ABAP interview questions and answers

1. What is an ABAP data dictionary?- ABAP 4 data dictionary describes the logical structures of the objects used in application development and shows how they are mapped to the underlying relational database in tables/views.
2. What are domains and data element?- Domains:Domain is the central object for describing the technical characteristics of an attribute of an business objects. It describes the value range of the field. Data Element: It is used to describe the semantic definition of the table fields like description the field. Data element describes how a field can be displayed to end-user.
3. What is foreign key relationship?- A relationship which can be defined between tables and must be explicitly defined at field level. Foreign keys are used to ensure the consistency of data. Data entered should be checked against existing data to ensure that there are now contradiction. While defining foreign key relationship cardinality has to be specified. Cardinality mentions how many dependent records or how referenced records are possible.
4. Describe data classes.- Master data: It is the data which is seldomly changed. Transaction data: It is the data which is often changed. Organization data: It is a customizing data which is entered in the system when the system is configured and is then rarely changed. System data:It is the data which R/3 system needs for itself.
5. What are indexes?- Indexes are described as a copy of a database table reduced to specific fields. This data exists in sorted form. This sorting form ease fast access to the field of the tables. In order that other fields are also read, a pointer to the associated record of the actual table are included in the index. Yhe indexes are activated along with the table and are created automatically with it in the database.
6. Difference between transparent tables and pooled tables.- Transparent tables: Transparent tables in the dictionary has a one-to-one relation with the table in database. Its structure corresponds to single database field. Table in the database has the same name as in the dictionary. Transparent table holds application data. Pooled tables. Pooled tables in the dictionary has a many-to-one relation with the table in database. Table in the database has the different name as in the dictionary. Pooled table are stored in table pool at the database level.
7. What is an ABAP/4 Query?- ABAP/4 Query is a powerful tool to generate simple reports without any coding. ABAP/4 Query can generate the following 3 simple reports: Basic List: It is the simple reports. Statistics: Reports with statistical functions like Average, Percentages. Ranked Lists: For analytical reports. - For creating a ABAP/4 Query, programmer has to create user group and a functional group. Functional group can be created using with or without logical database table. Finally, assign user group to functional group. Finally, create a query on the functional group generated.
8. What is BDC programming?- Transferring of large/external/legacy data into SAP system using Batch Input programming. Batch input is a automatic procedure referred to as BDC(Batch Data Communications).The central component of the transfer is a queue file which receives the data vie a batch input programs and groups associated data into “sessions”.
9. What are the functional modules used in sequence in BDC?- These are the 3 functional modules which are used in a sequence to perform a data transfer successfully using BDC programming: BDC_OPEN_GROUP - Parameters like Name of the client, sessions and user name are specified in this functional modules. BDC_INSERT - It is used to insert the data for one transaction into a session. BDC_CLOSE_GROUP - This is used to close the batch input session.
10. What are internal tables?- Internal tables are a standard data type object which exists only during the runtime of the program. They are used to perform table calculations on subsets of database tables and for re-organising the contents of database tables according to users need.
11. What is ITS? What are the merits of ITS?- ITS is a Internet Transaction Server. ITS forms an interface between HTTP server and R/3 system, which converts screen provided data by the R/3 system into HTML documents and vice-versa. Merits of ITS: A complete web transaction can be developed and tested in R/3 system. All transaction components, including those used by the ITS outside the R/3 system at runtime, can be stored in the R/3 system. The advantage of automatic language processing in the R/3 system can be utilized to language-dependent HTML documents at runtime.
12. What is DynPro?- DynPro is a Dynamic Programming which is a combination of screen and the associated flow logic Screen is also called as DynPro.
13. What are screen painter and menu painter?- Screen painter: Screen painter is a tool to design and maintain screen and its elements. It allows user to create GUI screens for the transactions. Attributes, layout, filed attributes and flow logic are the elements of Screen painter. Menu painter: Menu painter is a tool to design the interface components. Status, menu bars, menu lists, F-key settings, functions and titles are the components of Menu painters. Screen painter and menu painter both are the graphical interface of an ABAP/4 applications.
14. What are the components of SAP scripts?- SAP scripts is a word processing tool of SAP which has the following components: Standard text. It is like a standard normal documents. Layout sets. - Layout set consists of the following components: Windows and pages, Paragraph formats, Character formats. Creating forms in the R/3 system. Every layout set consists of Header, paragraph, and character string. ABAP/4 program.
15. What is ALV programming in ABAP? When is this grid used in ABAP?- ALV is Application List viewer. Sap provides a set of ALV (ABAP LIST VIEWER) function modules which can be put into use to embellish the output of a report. This set of ALV functions is used to enhance the readability and functionality of any report output. Cases arise in sap when the output of a report contains columns extending more than 255 characters in length. In such cases, this set of ALV functions can help choose selected columns and arrange the different columns from a report output and also save different variants for report display. This is a very efficient tool for dynamically sorting and arranging the columns from a report output. The report output can contain up to 90 columns in the display with the wide array of display options.
16. What are the events in ABAP/4 language?- Initialization, At selection-screen, Start-of-selection, end-of-selection, top-of-page, end-of-page, At line-selection, At user-command, At PF, Get, At New, At LAST, AT END, AT FIRST.
17. What is CTS and what do you know about it?- The Change and Transport System (CTS) is a tool that helps you to organize development projects in the ABAP Workbench and in Customizing, and then transport the changes between the SAP Systems and clients in your system landscape. This documentation provides you with an overview of how to manage changes with the CTS and essential information on setting up your system and client landscape and deciding on a transport strategy. Read and follow this documentation when planning your development project.
18. What are logical databases? What are the advantages/ dis-advantages of logical databases?- To read data from a database tables we use logical database. A logical database provides read-only access to a group of related tables to an ABAP/4 program. Advantages: i)check functions which check that user input is complete, correct,and plausible. ii)Meaningful data selection. iii)central authorization checks for database accesses. iv)good read access performance while retaining the hierarchical data view determined by the application logic. dis advantages: i)If you donot specify a logical database in the program attributes,the GET events never occur. ii)There is no ENDGET command,so the code block associated with an event ends with the next event statement (such as another GET or an END-OF-SELECTION).
19. What is a batch input session?- BATCH INPUT SESSION is an intermediate step between internal table and database table. Data along with the action is stored in session ie data for screen fields, to which screen it is passed, program name behind it, and how next screen is processed.
20. How to upload data using CATT ?- These are the steps to be followed to Upload data through CATT: Creation of the CATT test case & recording the sample data input. Download of the source file template. Modification of the source file. Upload of the data from the source file.
21. What is Smart Forms?- Smart Forms allows you to create forms using a graphical design tool with robust functionality, color, and more. Additionally, all new forms developed at SAP will be created with the new Smart Form solution.
22. How can I make a differentiation between dependent and independent data?- Client dependent or independent transfer requirements include client specific or cross client objects in the change requests. Workbench objects like SAPscripts are client specific, some entries in customizing are client independent. If you display the object list for one change request, and then for each object the object attributes, you will find the flag client specific. If one object in the task list has this flag on, then that transport will be client dependent.
23. What is the difference between macro and subroutine?- Macros can only be used in the program the are defined in and only after the definition are expanded at compilation / generation. Subroutines (FORM) can be called from both the program the are defined in and other programs . A MACRO is more or less an abbreviation for some lines of code that are used more than once or twice. A FORM is a local subroutine (which can be called external). A FUNCTION is (more or less) a subroutine that is called external. Since debugging a MACRO is not really possible, prevent the use of them (I’ve never used them, but seen them in action). If the subroutine is used only local (called internal) use a FORM. If the subroutine is called external (used by more than one program) use a FUNCTION.

C# interview questions and answers

1. What’s the advantage of using System.Text.StringBuilder over System.String? StringBuilder is more efficient in the cases, where a lot of manipulation is done to the text. Strings are immutable, so each time it’s being operated on, a new instance is created.
2. Can you store multiple data types in System.Array? No.
3. What’s the difference between the System.Array.CopyTo() and System.Array.Clone()? The first one performs a deep copy of the array, the second one is shallow.
4. How can you sort the elements of the array in descending order? By calling Sort() and then Reverse() methods.
5. What’s the .NET datatype that allows the retrieval of data by a unique key? HashTable.
6. What’s class SortedList underneath? A sorted HashTable.
7. Will finally block get executed if the exception had not occurred? Yes.
8. What’s the C# equivalent of C++ catch (…), which was a catch-all statement for any possible exception? A catch block that catches the exception of type System.Exception. You can also omit the parameter data type in this case and just write catch {}.
9. Can multiple catch blocks be executed? No, once the proper catch code fires off, the control is transferred to the finally block (if there are any), and then whatever follows the finally block.
10. Why is it a bad idea to throw your own exceptions? Well, if at that point you know that an error has occurred, then why not write the proper code to handle that error instead of passing a new Exception object to the catch block? Throwing your own exceptions signifies some design flaws in the project.
11. What’s a delegate? A delegate object encapsulates a reference to a method. In C++ they were referred to as function pointers.
12. What’s a multicast delegate? It’s a delegate that points to and eventually fires off several methods.
13. How’s the DLL Hell problem solved in .NET? Assembly versioning allows the application to specify not only the library it needs to run (which was available under Win32), but also the version of the assembly.
14. What are the ways to deploy an assembly? An MSI installer, a CAB archive, and XCOPY command.
15. What’s a satellite assembly? When you write a multilingual or multi-cultural application in .NET, and want to distribute the core application separately from the localized modules, the localized assemblies that modify the core application are called satellite assemblies.
16. What namespaces are necessary to create a localized application? System.Globalization, System.Resources.
17. What’s the difference between // comments, /* */ comments and /// comments? Single-line, multi-line and XML documentation comments.
18. How do you generate documentation from the C# file commented properly with a command-line compiler? Compile it with a /doc switch.
19. What’s the difference between and XML documentation tag? Single line code example and multiple-line code example.
20. Is XML case-sensitive? Yes, so and are different elements.
21. What debugging tools come with the .NET SDK? CorDBG – command-line debugger, and DbgCLR – graphic debugger. Visual Studio .NET uses the DbgCLR. To use CorDbg, you must compile the original C# file using the /debug switch.
22. What does the This window show in the debugger? It points to the object that’s pointed to by this reference. Object’s instance data is shown.
23. What does assert() do? In debug compilation, assert takes in a Boolean condition as a parameter, and shows the error dialog if the condition is false. The program proceeds without any interruption if the condition is true.
24. What’s the difference between the Debug class and Trace class? Documentation looks the same. Use Debug class for debug builds, use Trace class for both debug and release builds.
25. Why are there five tracing levels in System.Diagnostics.TraceSwitcher? The tracing dumps can be quite verbose and for some applications that are constantly running you run the risk of overloading the machine and the hard drive there. Five levels range from None to Verbose, allowing to fine-tune the tracing activities.
26. Where is the output of TextWriterTraceListener redirected? To the Console or a text file depending on the parameter passed to the constructor.
27. How do you debug an ASP.NET Web application? Attach the aspnet_wp.exe process to the DbgClr debugger.
28. What are three test cases you should go through in unit testing? Positive test cases (correct data, correct output), negative test cases (broken or missing data, proper handling), exception test cases (exceptions are thrown and caught properly).
29. Can you change the value of a variable while debugging a C# application? Yes, if you are debugging via Visual Studio.NET, just go to Immediate window.
30. Explain the three services model (three-tier application). Presentation (UI), business (logic and underlying code) and data (from storage or other sources).
31. What are advantages and disadvantages of Microsoft-provided data provider classes in ADO.NET? SQLServer.NET data provider is high-speed and robust, but requires SQL Server license purchased from Microsoft. OLE-DB.NET is universal for accessing other sources, like Oracle, DB2, Microsoft Access and Informix, but it’s a .NET layer on top of OLE layer, so not the fastest thing in the world. ODBC.NET is a deprecated layer provided for backward compatibility to ODBC engines.
32. What’s the role of the DataReader class in ADO.NET connections? It returns a read-only dataset from the data source when the command is executed.
33. What is the wildcard character in SQL? Let’s say you want to query database with LIKE for all employees whose name starts with La. The wildcard character is %, the proper query with LIKE would involve ‘La%’.
34. Explain ACID rule of thumb for transactions. Transaction must be Atomic (it is one unit of work and does not dependent on previous and following transactions), Consistent (data is either committed or roll back, no “in-between” case where something has been updated and something hasn’t), Isolated (no transaction sees the intermediate results of the current transaction), Durable (the values persist if the data had been committed even if the system crashes right after).
35. What connections does Microsoft SQL Server support? Windows Authentication (via Active Directory) and SQL Server authentication (via Microsoft SQL Server username and passwords).
36. Which one is trusted and which one is untrusted? Windows Authentication is trusted because the username and password are checked with the Active Directory, the SQL Server authentication is untrusted, since SQL Server is the only verifier participating in the transaction.
37. Why would you use untrusted verificaion? Web Services might use it, as well as non-Windows applications.
38. What does the parameter Initial Catalog define inside Connection String? The database name to connect to.
39. What’s the data provider name to connect to Access database? Microsoft.Access.
40. What does Dispose method do with the connection object? Deletes it from the memory.
41. What is a pre-requisite for connection pooling? Multiple processes must agree that they will share the same connection, where every parameter is the same, including the security settings.

SQL Server 2008 Interview Questions

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MS SQL Server interview questions

1. What is normalization? - Well a relational database is basically composed of tables that contain related data. So the Process of organizing this data into tables is actually referred to as normalization.
2. What is a Stored Procedure? - Its nothing but a set of T-SQL statements combined to perform a single task of several tasks. Its basically like a Macro so when you invoke the Stored procedure, you actually run a set of statements.
3. Can you give an example of Stored Procedure? - sp_helpdb , sp_who2, sp_renamedb are a set of system defined stored procedures. We can also have user defined stored procedures which can be called in similar way.
4. What is a trigger? - Triggers are basically used to implement business rules. Triggers is also similar to stored procedures. The difference is that it can be activated when data is added or edited or deleted from a table in a database.
5. What is a view? - If we have several tables in a db and we want to view only specific columns from specific tables we can go for views. It would also suffice the needs of security some times allowing specfic users to see only specific columns based on the permission that we can configure on the view. Views also reduce the effort that is required for writing queries to access specific columns every time.
6. What is an Index? - When queries are run against a db, an index on that db basically helps in the way the data is sorted to process the query for faster and data retrievals are much faster when we have an index.
7. What are the types of indexes available with SQL Server? - There are basically two types of indexes that we use with the SQL Server. Clustered and the Non-Clustered.
8. What is the basic difference between clustered and a non-clustered index? - The difference is that, Clustered index is unique for any given table and we can have only one clustered index on a table. The leaf level of a clustered index is the actual data and the data is resorted in case of clustered index. Whereas in case of non-clustered index the leaf level is actually a pointer to the data in rows so we can have as many non-clustered indexes as we can on the db.
9. What are cursors? - Well cursors help us to do an operation on a set of data that we retreive by commands such as Select columns from table. For example : If we have duplicate records in a table we can remove it by declaring a cursor which would check the records during retreival one by one and remove rows which have duplicate values.
10. When do we use the UPDATE_STATISTICS command? - This command is basically used when we do a large processing of data. If we do a large amount of deletions any modification or Bulk Copy into the tables, we need to basically update the indexes to take these changes into account. UPDATE_STATISTICS updates the indexes on these tables accordingly.
11. Which TCP/IP port does SQL Server run on? - SQL Server runs on port 1433 but we can also change it for better security.
12. From where can you change the default port? - From the Network Utility TCP/IP properties –> Port number.both on client and the server.
13. Can you tell me the difference between DELETE & TRUNCATE commands? - Delete command removes the rows from a table based on the condition that we provide with a WHERE clause. Truncate will actually remove all the rows from a table and there will be no data in the table after we run the truncate command.
14. Can we use Truncate command on a table which is referenced by FOREIGN KEY? - No. We cannot use Truncate command on a table with Foreign Key because of referential integrity.
15. What is the use of DBCC commands? - DBCC stands for database consistency checker. We use these commands to check the consistency of the databases, i.e., maintenance, validation task and status checks.
16. Can you give me some DBCC command options?(Database consistency check) - DBCC CHECKDB - Ensures that tables in the db and the indexes are correctly linked.and DBCC CHECKALLOC - To check that all pages in a db are correctly allocated. DBCC SQLPERF - It gives report on current usage of transaction log in percentage. DBCC CHECKFILEGROUP - Checks all tables file group for any damage.
17. What command do we use to rename a db? - sp_renamedb ‘oldname’ , ‘newname’
18. Well sometimes sp_reanmedb may not work you know because if some one is using the db it will not accept this command so what do you think you can do in such cases? - In such cases we can first bring to db to single user using sp_dboptions and then we can rename that db and then we can rerun the sp_dboptions command to remove the single user mode.
19. What is the difference between a HAVING CLAUSE and a WHERE CLAUSE? - Having Clause is basically used only with the GROUP BY function in a query. WHERE Clause is applied to each row before they are part of the GROUP BY function in a query.
20. What do you mean by COLLATION? - Collation is basically the sort order. There are three types of sort order Dictionary case sensitive, Dictonary - case insensitive and Binary.
21. What is a Join in SQL Server? - Join actually puts data from two or more tables into a single result set.
22. Can you explain the types of Joins that we can have with Sql Server? - There are three types of joins: Inner Join, Outer Join, Cross Join
23. When do you use SQL Profiler? - SQL Profiler utility allows us to basically track connections to the SQL Server and also determine activities such as which SQL Scripts are running, failed jobs etc..
24. What is a Linked Server? - Linked Servers is a concept in SQL Server by which we can add other SQL Server to a Group and query both the SQL Server dbs using T-SQL Statements.
25. Can you link only other SQL Servers or any database servers such as Oracle? - We can link any server provided we have the OLE-DB provider from Microsoft to allow a link. For Oracle we have a OLE-DB provider for oracle that microsoft provides to add it as a linked server to the sql server group.
26. Which stored procedure will you be running to add a linked server? - sp_addlinkedserver, sp_addlinkedsrvlogin
27. What are the OS services that the SQL Server installation adds? - MS SQL SERVER SERVICE, SQL AGENT SERVICE, DTC (Distribution transac co-ordinator)
28. Can you explain the role of each service? - SQL SERVER - is for running the databases SQL AGENT - is for automation such as Jobs, DB Maintanance, Backups DTC - Is for linking and connecting to other SQL Servers
29. How do you troubleshoot SQL Server if its running very slow? - First check the processor and memory usage to see that processor is not above 80% utilization and memory not above 40-45% utilization then check the disk utilization using Performance Monitor, Secondly, use SQL Profiler to check for the users and current SQL activities and jobs running which might be a problem. Third would be to run UPDATE_STATISTICS command to update the indexes
30. Lets say due to N/W or Security issues client is not able to connect to server or vice versa. How do you troubleshoot? - First I will look to ensure that port settings are proper on server and client Network utility for connections. ODBC is properly configured at client end for connection ——Makepipe & readpipe are utilities to check for connection. Makepipe is run on Server and readpipe on client to check for any connection issues.
31. What are the authentication modes in SQL Server? - Windows mode and mixed mode (SQL & Windows).
32. Where do you think the users names and passwords will be stored in sql server? - They get stored in master db in the sysxlogins table.
33. What is log shipping? Can we do logshipping with SQL Server 7.0 - Logshipping is a new feature of SQL Server 2000. We should have two SQL Server - Enterprise Editions. From Enterprise Manager we can configure the logshipping. In logshipping the transactional log file from one server is automatically updated into the backup database on the other server. If one server fails, the other server will have the same db and we can use this as the DR (disaster recovery) plan.
34. Let us say the SQL Server crashed and you are rebuilding the databases including the master database what procedure to you follow? - For restoring the master db we have to stop the SQL Server first and then from command line we can type SQLSERVER –m which will basically bring it into the maintenance mode after which we can restore the master db.
35. Let us say master db itself has no backup. Now you have to rebuild the db so what kind of action do you take? - (I am not sure- but I think we have a command to do it).
36. What is BCP? When do we use it? - BulkCopy is a tool used to copy huge amount of data from tables and views. But it won’t copy the structures of the same.
37. What should we do to copy the tables, schema and views from one SQL Server to another? - We have to write some DTS packages for it.
38. What are the different types of joins and what dies each do?
39. What are the four main query statements?
40. What is a sub-query? When would you use one?
41. What is a NOLOCK?
42. What are three SQL keywords used to change or set someone’s permissions?
43. What is the difference between HAVING clause and the WHERE clause?
44. What is referential integrity? What are the advantages of it?
45. What is database normalization?
46. Which command using Query Analyzer will give you the version of SQL server and operating system?
47. Using query analyzer, name 3 ways you can get an accurate count of the number of records in a table?
48. What is the purpose of using COLLATE in a query?
49. What is a trigger?
50. What is one of the first things you would do to increase performance of a query? For example, a boss tells you that “a query that ran yesterday took 30 seconds, but today it takes 6 minutes”
51. What is an execution plan? When would you use it? How would you view the execution plan?
52. What is the STUFF function and how does it differ from the REPLACE function?
53. What does it mean to have quoted_identifier on? What are the implications of having it off?
54. What are the different types of replication? How are they used?
55. What is the difference between a local and a global variable?
56. What is the difference between a Local temporary table and a Global temporary table? How is each one used?
57. What are cursors? Name four types of cursors and when each one would be applied?
58. What is the purpose of UPDATE STATISTICS?
59. How do you use DBCC statements to monitor various aspects of a SQL server installation?
60. How do you load large data to the SQL server database?
61. How do you check the performance of a query and how do you optimize it?
62. How do SQL server 2000 and XML linked? Can XML be used to access data?
63. What is SQL server agent?
64. What is referential integrity and how is it achieved?
65. What is indexing?
66. What is normalization and what are the different forms of normalizations?
67. Difference between server.transfer and server.execute method?
68. What id de-normalization and when do you do it?
69. What is better - 2nd Normal form or 3rd normal form? Why?
70. Can we rewrite subqueries into simple select statements or with joins? Example?
71. What is a function? Give some example?
72. What is a stored procedure?
73. Difference between Function and Procedure-in general?
74. Difference between Function and Stored Procedure?
75. Can a stored procedure call another stored procedure. If yes what level and can it be controlled?
76. Can a stored procedure call itself(recursive). If yes what level and can it be controlled.?
77. How do you find the number of rows in a table?
78. Difference between Cluster and Non-cluster index?
79. What is a table called, if it does not have neither Cluster nor Non-cluster Index?
80. Explain DBMS, RDBMS?
81. Explain basic SQL queries with SELECT from where Order By, Group By-Having?
82. Explain the basic concepts of SQL server architecture?
83. Explain couple pf features of SQL server
84. Scalability, Availability, Integration with internet, etc.)?
85. Explain fundamentals of Data ware housing & OLAP?
86. Explain the new features of SQL server 2000?
87. How do we upgrade from SQL Server 6.5 to 7.0 and 7.0 to 2000?
88. What is data integrity? Explain constraints?
89. Explain some DBCC commands?
90. Explain sp_configure commands, set commands?
91. Explain what are db_options used for?
92. What is the basic functions for master, msdb, tempdb databases?
93. What is a job?
94. What are tasks?
95. What are primary keys and foreign keys?
96. How would you Update the rows which are divisible by 10, given a set of numbers in column?
97. If a stored procedure is taking a table data type, how it looks?
98. How m-m relationships are implemented?
99. How do you know which index a table is using?
100. How will oyu test the stored procedure taking two parameters namely first name and last name returning full name?
101. How do you find the error, how can you know the number of rows effected by last SQL statement?
102. How can you get @@error and @@rowcount at the same time?
103. What are sub-queries? Give example? In which case sub-queries are not feasible?
104. What are the type of joins? When do we use Outer and Self joins?
105. Which virtual table does a trigger use?
106. How do you measure the performance of a stored procedure?
107. Questions regarding Raiseerror?
108. Questions on identity?
109. If there is failure during updation of certain rows, what will be the state?

C# Questions

Question: What’s the implicit name of the parameter that gets passed into the class’ set method?
Answer: Value, and its datatype depends on whatever variable we’re changing.

Question: How do you inherit from a class in C#?
Answer Place a colon and then the name of the base class. Notice that it’s double colon in C++.

Question: Does C# support multiple inheritance?
Answer No, use interfaces instead.

Question When you inherit a protected class-level variable, who is it available to?
Answer: Classes in the same namespace.

Question Are private class-level variables inherited?
Answer: Yes, but they are not accessible, so looking at it you can honestly say that they are not inherited. But they are.

Question Describe the accessibility modifier protected internal.
Answer: It’s available to derived classes and classes within the same Assembly (and naturally from the base class it’s declared in).

Question C# provides a default constructor for me. I write a constructor that takes a string as a parameter, but want to keep the no parameter one. How many constructors should I write?
Answer: Two. Once you write at least one constructor, C# cancels the freebie constructor, and now you have to write one yourself, even if there’s no implementation in it.

Question What’s the top .NET class that everything is derived from?
Answer: System.Object.

Question How’s method overriding different from overloading?
Answer: When overriding, you change the method behavior for a derived class. Overloading simply involves having a method with the same name within the class.

Question What does the keyword virtual mean in the method definition?
Answer: The method can be over-ridden.

Question Can you declare the override method static while the original method is non-static?
Answer: No, you can’t, the signature of the virtual method must remain the same, only the keyword virtual is changed to keyword override.

Question Can you override private virtual methods?
Answer: No, moreover, you cannot access private methods in inherited classes, have to be protected in the base class to allow any sort of access.

Question Can you prevent your class from being inherited and becoming a base class for some other classes?
Answer: Yes, that’s what keyword sealed in the class definition is for. The developer trying to derive from your class will get a message: cannot inherit from Sealed class WhateverBaseClassName. It’s the same concept as final class in Java.

Question Can you allow class to be inherited, but prevent the method from being over-ridden?
Answer: Yes, just leave the class public and make the method sealed.

Question What’s an abstract class?
Answer: A class that cannot be instantiated. A concept in C++ known as pure virtual method. A class that must be inherited and have the methods over-ridden. Essentially, it’s a blueprint for a class without any implementation.

Question When do you absolutely have to declare a class as abstract (as opposed to free-willed educated choice or decision based on UML diagram)?
Answer: When at least one of the methods in the class is abstract. When the class itself is inherited from an abstract class, but not all base abstract methods have been over-ridden.

Question What’s an interface class?
Answer: It’s an abstract class with public abstract methods all of which must be implemented in the inherited classes.

Question Why can’t you specify the accessibility modifier for methods inside the interface?
Answer: They all must be public. Therefore, to prevent you from getting the false impression that you have any freedom of choice, you are not allowed to specify any accessibility, it’s public by default.

Question Can you inherit multiple interfaces?
Answer: Yes, why not.

Question What’s the difference between an interface and abstract class?
Answer: In the interface all methods must be abstract; in the abstract class some methods can be concrete. In the interface no accessibility modifiers are allowed, which is ok in abstract classes.

Question How can you overload a method?
Answer: Different parameter data types, different number of parameters, different order of parameters.

Question If a base class has a bunch of overloaded constructors, and an inherited class has another bunch of overloaded constructors, can you enforce a call from an inherited constructor to an arbitrary base constructor?
Answer: Yes, just place a colon, and then keyword base (parameter list to invoke the appropriate constructor) in the overloaded constructor definition inside the inherited class.

Question What’s the difference between System.String and System.StringBuilder classes?
Answer: System.String is immutable; System.StringBuilder was designed with the purpose of having a mutable string where a variety of operations can be performed.

Question What’s the advantage of using System.Text.StringBuilder over System.String?
Answer: StringBuilder is more efficient in the cases, where a lot of manipulation is done to the text. Strings are immutable, so each time it’s being operated on, a new instance is created.

Question Can you store multiple data types in System.Array?
Answer: No.

Question What’s the difference between the System.Array.CopyTo() and System.Array.Clone()?
Answer: The first one performs a deep copy of the array, the second one is shallow.

Question How can you sort the elements of the array in descending order?
Answer: By calling Sort() and then Reverse() methods.

Question What’s the .NET datatype that allows the retrieval of data by a unique key?
Answer: HashTable.

Question What’s class SortedList underneath?
Answer: A sorted HashTable.

Question Will finally block get executed if the exception had not occurred?
Answer: Yes.

Question What’s the C# equivalent of C++ catch (…), which was a catch-all statement for any possible exception?
Answer: A catch block that catches the exception of type System.Exception. You can also omit the parameter data type in this case and just write catch {}.

Question Can multiple catch blocks be executed?
Answer: No, once the proper catch code fires off, the control is transferred to the finally block (if there are any), and then whatever follows the finally block.

Question Why is it a bad idea to throw your own exceptions?
Answer: Well, if at that point you know that an error has occurred, then why not write the proper code to handle that error instead of passing a new Exception object to the catch block? Throwing your own exceptions signifies some design flaws in the project.

Question What’s a delegate?
Answer: A delegate object encapsulates a reference to a method. In C++ they were referred to as function pointers.

Question What’s a multicast delegate?
Answer: It’s a delegate that points to and eventually fires off several methods.

Question How’s the DLL Hell problem solved in .NET?
Answer: Assembly versioning allows the application to specify not only the library it needs to run (which was available under Win32), but also the version of the assembly.

Question What are the ways to deploy an assembly?
Answer: An MSI installer, a CAB archive, and XCOPY command.



Question What’s a satellite assembly?
Answer: When you write a multilingual or multi-cultural application in .NET, and want to distribute the core application separately from the localized modules, the localized assemblies that modify the core application are called satellite assemblies.

Question What namespaces are necessary to create a localized application?
Answer: System.Globalization, System.Resources.

Question What’s the difference between // comments, /* */ comments and /// comments?
Answer: Single-line, multi-line and XML documentation comments.

Question How do you generate documentation from the C# file commented properly with a command-line compiler?
Answer: Compile it with a /doc switch.

Question What’s the difference between and XML documentation tag?
Answer: Single line code example and multiple-line code example.

Question Is XML case-sensitive?
Answer: Yes, so and are different elements.

Question What debugging tools come with the .NET SDK?
Answer: CorDBG – command-line debugger, and DbgCLR – graphic debugger. Visual Studio .NET uses the DbgCLR. To use CorDbg, you must compile the original C# file using the /debug switch.

Question What does the This window show in the debugger?
Answer: It points to the object that’s pointed to by this reference. Object’s instance data is shown.

Question What does assert() do?
Answer: In debug compilation, assert takes in a Boolean condition as a parameter, and shows the error dialog if the condition is false. The program proceeds without any interruption if the condition is true.

Question What’s the difference between the Debug class and Trace class?
Answer: Documentation looks the same. Use Debug class for debug builds, use Trace class for both debug and release builds.

Question Why are there five tracing levels in System.Diagnostics.TraceSwitcher?
Answer: The tracing dumps can be quite verbose and for some applications that are constantly running you run the risk of overloading the machine and the hard drive there. Five levels range from None to Verbose, allowing to fine-tune the tracing activities.

Question Where is the output of TextWriterTraceListener redirected? To the Console or a text file depending on the parameter passed to the constructor.

Question How do you debug an ASP.NET Web application?

Answer: Attach the aspnet_wp.exe process to the DbgClr debugger.

Question What are three test cases you should go through in unit testing?
Answer: Positive test cases (correct data, correct output), negative test cases (broken or missing data, proper handling), exception test cases (exceptions are thrown and caught properly).



Question Can you change the value of a variable while debugging a C# application?
Answer: Yes, if you are debugging via Visual Studio.NET, just go to Immediate window.

Question Explain the three services model (three-tier application). Presentation (UI), business (logic and underlying code) and data (from storage or other sources).

Question What are advantages and disadvantages of Microsoft-provided data provider classes in ADO.NET?

Answer: SQLServer.NET data provider is high-speed and robust, but requires SQL Server license purchased from Microsoft. OLE-DB.NET is universal for accessing other sources, like Oracle, DB2, Microsoft Access and Informix, but it’s a .NET layer on top of OLE layer, so not the fastest thing in the world. ODBC.NET is a deprecated layer provided for backward compatibility to ODBC engines.
Question What’s the role of the DataReader class in ADO.NET connections?
Answer: It returns a read-only dataset from the data source when the command is executed.

Question What is the wildcard character in SQL?
Answer: Let’s say you want to query database with LIKE for all employees whose name starts with La. The wildcard character is %, the proper query with LIKE would involve ‘La%’.

Question Explain ACID rule of thumb for transactions. Transaction must be Atomic (it is one unit of work and does not dependent on previous and following transactions), Consistent (data is either committed or roll back, no “in-between” case where something has been updated and something hasn’t), Isolated (no transaction sees the intermediate results of the current transaction), Durable (the values persist if the data had been committed even if the system crashes right after).

Question What connections does Microsoft SQL Server support?

Answer: Windows Authentication (via Active Directory) and SQL Server authentication (via Microsoft SQL Server username and passwords).

Question Which one is trusted and which one is untrusted?
Answer: Windows Authentication is trusted because the username and password are checked with the Active Directory, the SQL Server authentication is untrusted, since SQL Server is the only verifier participating in the transaction.

Question Why would you use untrusted verificaion?
Answer: Web Services might use it, as well as non-Windows applications.

Question What does the parameter Initial Catalog define inside Connection String? The database name to connect to.

Question What’s the data provider name to connect to Access database?
Answer: Microsoft.Access.

Question What does Dispose method do with the connection object?
Answer: Deletes it from the memory.

Question What is a pre-requisite for connection pooling?
Answer: Multiple processes must agree that they will share the same connection, where every parameter is the same, including the security settings.

1.Does C# support multiple-inheritance?
No. But you can use Interfaces.

2.Where is a protected class-level variable available?
It is available to any sub-class derived from base class

3.Are private class-level variables inherited?
Yes, but they are not accessible.


4.Describe the accessibility modifier “protected internal”.
It is available to classes that are within the same assembly and derived from the specified base class.

6.Which class is at the top of .NET class hierarchy?
System.Object.

7.What does the term immutable mean?
The data value may not be changed.
Note: The variable value may be changed, but the original immutable data value was discarded and a new data value was created in memory.

8.What’s the difference between System.String and System.Text.StringBuilder classes?
System.String is immutable.
System.StringBuilder was designed with the purpose of having a mutable string where a variety of operations can be performed.

9.What’s the advantage of using System.Text.StringBuilder over System.String?

StringBuilder is more efficient in cases where there is a large amount of string manipulation. Strings are immutable, so each time a string is changed, a new instance in memory is created.

10.Can you store multiple data types in System.Array?
No.

11.What’s the difference between the System.Array.CopyTo() and System.Array.Clone()?
The Clone() method returns a new array (a shallow copy) object containing all the elements in the original array. The CopyTo() method copies the elements into another existing array. Both perform a shallow copy. A shallow copy means the contents (each array element) contains references to the same object as the elements in the original array. A deep copy (which neither of these methods performs) would create a new instance of each element's object, resulting in a different, yet identacle object.

12.How can you sort the elements of the array in descending order?
By calling Sort() and then Reverse() methods.

13.What’s the .NET collection class that allows an element to be accessed using a unique key?
HashTable.

14.What class is underneath the SortedList class?
A sorted HashTable.

15.Will the finally block get executed if an exception has not occurred?
Yes.

16.What’s the C# syntax to catch any possible exception?
A catch block that catches the exception of type System.Exception. You can also omit the parameter data type in this case and just write catch {}.

17.Can multiple catch blocks be executed for a single try statement?
No. Once the proper catch block processed, control is transferred to the finally block .

18.Explain the three services model commonly know as a three-tier application?
Presentation (UI), Business (logic and underlying code) and Data (from storage or other sources).

Class Questions

1.What is the syntax to inherit from a class in C#?
Place a colon and then the name of the base class.
Example: class MyNewClass : MyBaseClass

2.Can you prevent your class from being inherited by another class?
Yes. The keyword “sealed” will prevent the class from being inherited.

3.Can you allow a class to be inherited, but prevent the method from being over-ridden?
Yes. Just leave the class public and make the method sealed.

4.What’s an abstract class?
A class that cannot be instantiated. An abstract class is a class that must be inherited and have the methods overridden. An abstract class is essentially a blueprint for a class without any implementation.

5.When do you absolutely have to declare a class as abstract?

1. When the class itself is inherited from an abstract class, but not all base abstract methods have been overridden.

2. When at least one of the methods in the class is abstract.


6.What is an interface class?
Interfaces, like classes, define a set of properties, methods, and events. But unlike classes, interfaces do not provide implementation. They are implemented by classes, and defined as separate entities from classes.

7.Why can’t you specify the accessibility modifier for methods inside the interface?
They all must be public, and are therefore public by default.

8.Can you inherit multiple interfaces?
Yes. .NET does support multiple interfaces.

9.What happens if you inherit multiple interfaces and they have conflicting method names?
It’s up to you to implement the method inside your own class, so implementation is left entirely up to you. This might cause a problem on a higher-level scale if similarly named methods from different interfaces expect different data, but as far as compiler cares you’re okay.

10. What’s the difference between an interface and abstract class?
In an interface class, all methods are abstract - there is no implementation. In an abstract class some methods can be concrete. In an interface class, no accessibility modifiers are allowed. An abstract class may have accessibility modifiers.

11. What is the difference between a Struct and a Class?
Structs are value-type variables and are thus saved on the stack, additional overhead but faster retrieval. Another difference is that structs cannot inherit.

Method and Property Questions

1. What’s the implicit name of the parameter that gets passed into the set method/property of a class?
Value. The data type of the value parameter is defined by whatever data type the property is declared .

2. What does the keyword “virtual” declare for a method or property?
The method or property can be overridden.

3. How is method overriding different from method overloading?
When overriding a method, you change the behavior of the method for the derived class. Overloading a method simply involves having another method with the same name within the class.

4. Can you declare an override method to be static if the original method is not static?
No. The signature of the virtual method must remain the same. (Note: Only the keyword virtual is changed to keyword override)

5. What are the different ways a method can be overloaded?
Different parameter data types, different number of parameters, different order of parameters.

6. If a base class has a number of overloaded constructors, and an inheriting class has a number of overloaded constructors; can you enforce a call from an inherited constructor to a specific base constructor?
Yes, just place a colon, and then keyword base (parameter list to invoke the appropriate constructor) in the overloaded constructor definition inside the inherited class.

Events and Delegates

1. What’s a delegate?
A delegate object encapsulates a reference to a method.

2. What’s a multicast delegate?
A delegate that has multiple handlers assigned to it. Each assigned handler (method) is called.

3. What’s the implicit name of the parameter that gets passed into the class’ set method?
Value, and it’s datatype depends on whatever variable we’re changing.

4. How do you inherit from a class in C#?
Place a colon and then the name of the base class.

5. Does C# support multiple inheritance?
No, use interfaces instead.

6. When you inherit a protected class-level variable, who is it available to?
Classes in the same namespace.

7. Are private class-level variables inherited?
Yes, but they are not accessible, so looking at it you can honestly say that they are not inherited.

8. Describe the accessibility modifier protected internal.?
It’s available to derived classes and classes within the same Assembly (and naturally from the base class it’s declared in).

9. C# provides a default constructor for me. I write a constructor that takes a string as a parameter, but want to keep the no parameter one. How many constructors should I write?
Two. Once you write at least one constructor, C# cancels the freebie constructor, and now you have to write one yourself, even if there’s no implementation in it.

10. What’s the top .NET class that everything is derived from?
System.Object.

11. How’s method overriding different from overloading?
When overriding, you change the method behavior for a derived class. Overloading simply involves having a method with the same name within the class.

12. What does the keyword virtual mean in the method definition?
The method can be over-ridden.

13. Can you declare the override method static while the original method is non-static?
No, you can’t, the signature of the virtual method must remain the same, only the keyword virtual is changed to keyword override.

14. Can you override private virtual methods?
No, moreover, you cannot access private methods in inherited classes, have to be protected in the base class to allow any sort of access.

15. Can you prevent your class from being inherited and becoming a base class for some other classes?
Yes, that’s what keyword sealed in the class definition is for. The developer trying to derive from your class will get a message: cannot inherit from Sealed class WhateverBaseClassName.
It’s the same concept as final class in Java.

16. Can you allow class to be inherited, but prevent the method from being over-ridden?
Yes, just leave the class public and make the method sealed.

17. What’s an abstract class?
A class that cannot be instantiated. A concept in C++ known as pure virtual method. A class that must be inherited and have the methods over-ridden.
Essentially, it’s a blueprint for a class without any implementation.

18. When do you absolutely have to declare a class as abstract (as opposed to free-willed educated choice or decision based on UML diagram)?
When at least one of the methods in the class is abstract. When the class itself is inherited from an abstract class, but not all base abstract methods have been over-ridden.

19. What’s an interface class?
It’s an abstract class with public abstract methods all of which must be implemented in the inherited classes.

20. Why can’t you specify the accessibility modifier for methods inside the interface?
They all must be public. Therefore, to prevent you from getting the false impression that you have any freedom of choice, you are not allowed to specify any accessibility, it’s public by default.

21. Can you inherit multiple interfaces?
Yes, why not.

22. And if they have conflicting method names?
It’s up to you to implement the method inside your own class, so implementation is left entirely up to you.
This might cause a problem on a higher-level scale if similarly named methods from different interfaces expect different data, but as far as compiler cares you’re okay.

23. What’s the difference between an interface and abstract class?
In the interface all methods must be abstract, in the abstract class some methods can be concrete. In the interface no accessibility modifiers are allowed, which is ok in abstract classes.

24. How can you overload a method?
Different parameter data types, different number of parameters, different order of parameters.

25. If a base class has a bunch of overloaded constructors, and an inherited class has another bunch of overloaded constructors, can you enforce a call from an inherited constructor to an arbitrary base constructor?
Yes, just place a colon, and then keyword base (parameter list to invoke the appropriate constructor) in the overloaded constructor definition inside the inherited class.

26. What’s the difference between System.String and System.StringBuilder classes?
System.String is immutable, System.StringBuilder was designed with the purpose of having a mutable string where a variety of operations can be performed.

27. Is it namespace class or class namespace?
The .NET class library is organized into namespaces. Each namespace contains a functionally related group of classes so natural namespace comes first.

.NET Questions

1. Write a simple Windows Forms MessageBox statement.?

System.Windows.Forms.MessageBox.Show ("Hello, Windows Forms");

2. Can you write a class without specifying namespace? Which namespace does it belong to by default??

Yes, you can, then the class belongs to global namespace which has no name. For commercial products, naturally, you wouldn’t want global namespace.

3. You are designing a GUI application with a window and several widgets on it. The user then resizes the app window and sees a lot of grey space, while the widgets stay in place. What’s the problem?

One should use anchoring for correct resizing. Otherwise the default property of a widget on a form is top-left, so it stays at the same location when resized.

4. How can you save the desired properties of Windows Forms application?
.config files in .NET are supported through the API to allow storing and retrieving information.

They are nothing more than simple XML files, sort of like what .ini files were before for Win32 apps.

5. So how do you retrieve the customized properties of a .NET application from XML .config file?

Initialize an instance of AppSettingsReader class. Call the GetValue method of AppSettingsReader class, passing in the name of the property and the type expected. Assign the result to the appropriate variable.

6. Can you automate this process?

In Visual Studio yes, use Dynamic Properties for automatic .config creation, storage and retrieval.

7. My progress bar freezes up and dialog window shows blank, when an intensive background process takes over.

Yes, you should’ve multi-threaded your GUI, with taskbar and main form being one thread, and the background process being the other.

8. What’s the safest way to deploy a Windows Forms app?

Web deployment: the user always downloads the latest version of the code; the program runs within security sandbox, properly written app will not require additional security privileges.

9. Why is it not a good idea to insert code into InitializeComponent method when working with Visual Studio?

The designer will likely throw it away; most of the code inside InitializeComponent is auto-generated.

10. What’s the difference between WindowsDefaultLocation and WindowsDefaultBounds?

WindowsDefaultLocation tells the form to start up at a location selected by OS, but with internally specified size. WindowsDefaultBounds delegates both size and starting position choices to the OS.

11. What’s the difference between Move and LocationChanged? Resize and SizeChanged?

Both methods do the same, Move and Resize are the names adopted from VB to ease migration to C#.

12. How would you create a non-rectangular window, let’s say an ellipse?

Create a rectangular form, set the TransparencyKey property to the same value as BackColor, which will effectively make the background of the form transparent. Then set the FormBorderStyle to FormBorderStyle.None, which will remove the contour and contents of the form.

13. How do you create a separator in the Menu Designer?

A hyphen ‘-’ would do it. Also, an ampersand ‘&\’ would underline the next letter.

14. How’s anchoring different from docking?

Anchoring treats the component as having the absolute size and adjusts its location relative to the parent form. Docking treats the component location as absolute and disregards the component size. So if a status bar must always be at the bottom no matter what, use docking. If a button should be on the top right, but change its position with the form being resized, use anchoring.

New Technologies

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Here we discuss the new technologies available in current trend.