C# Interview Questions And Answers Part - 6

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 is 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.


Why do I get a security exception when I try to run my C# app?
Some security exceptions are thrown if you are working on a network share. There are some parts of the frameworks that will not run if being run off a share (roaming profile, mapped drives, etc.). To see if this is what's happening, just move the executable over to your local drive and see if it runs without the exceptions. One of the common exceptions thrown under these conditions is
System.Security.SecurityException.
To get around this, you can change your security policy for the intranet zone, code group 1.2, (the zone that running off shared folders falls into) by using the caspol.exe tool.


Is there any sample C# code for simple threading?
Some sample code follows: using System;
using System.Threading;
class ThreadTest
{
public void runme()
{
Console.WriteLine("Runme Called");
}
public static void Main(String[] args)
{
ThreadTest b = new ThreadTest();
Thread t = new Thread(new ThreadStart(b.runme));
t.Start();
}
}


What is the difference between // comments, /* */ comments and /// comments?
Single-line, multi-line and XML documentation comments.


What is the difference between and XML documentation tag?
Single line code example and multiple-line code example.


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


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).


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


How do I port "synchronized" functions from Visual J++ to C#?
Original Visual J++ code: public synchronized void Run()
{
// function body
}
Ported C# code: class C
{
public void Run()
{
lock(this)
{
// function body
}
}
public static void Main() {}
}


Can I define a type that is an alias of another type (like typedef in C++)?
Not exactly. You can create an alias within a single file with the "using" directive: using System; using Integer = System.Int32; // alias
But you can't create a true alias, one that extends beyond the file in which it is declared. Refer to the C# spec for more info on the 'using' statement's scope.


Is it possible to have different access modifiers on the get/set methods of a property?
No. The access modifier on a property applies to both its get and set accessors. What you need to do if you want them to be different is make the property read-only (by only providing a get accessor) and create a private/internal set method that is separate from the property.


Is it possible to have a static indexer in C#?
No. Static indexers are not allowed in C#.


Does C# support #define for defining global constants?
No. If you want to get something that works like the following C code:
#define A 1
use the following C# code: class MyConstants
{
public const int A = 1;
}
Then you use MyConstants.A where you would otherwise use the A macro.
Using MyConstants.A has the same generated code as using the literal 1.


Does C# support templates?
No. However, there are plans for C# to support a type of template known as a generic. These generic types have similar syntax but are instantiated at run time as opposed to compile time. You can read more about them here.


Does C# support parameterized properties?
No. C# does, however, support the concept of an indexer from language spec. An indexer is a member that enables an object to be indexed in the same way as an array. Whereas properties enable field-like access, indexers enable array-like access. As an example, consider the Stack class presented earlier. The designer of this class may want to expose array-like access so that it is possible to inspect or alter the items on the stack without performing unnecessary Push and Pop operations. That is, Stack is implemented as a linked list, but it also provides the convenience of array access.
Indexer declarations are similar to property declarations, with the main differences being that indexers are nameless (the name used in the declaration is this, since this is being indexed) and that indexers include indexing parameters. The indexing parameters are provided between square brackets.


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