Useful for preparation, but too specific to be used in the interview.
Yes. The code in the finally always runs. If you return out of the try block, or even if you do a “goto” out of the try, the finally block always runs: using System; class main { public static void Main() { try { Console.WriteLine("In Try block"); return; } finally { Console.WriteLine("In Finally block"); } } } Both “In Try block” and “In Finally block” will be displayed. Whether the return is in the try block or after the try-finally block, performance is not affected either way. The compiler treats it as if the return were outside the try block anyway. If it’s a return without an expression (as it is above), the IL emitted is identical whetherthe return is inside or outside of the try. If the return has an expression, there’s an extra store/load of the value of the expression (since it has to be computed within the try block).
Note that in an IDE-created project, by convention, these attributes are placed in AssemblyInfo.cs.
[Obsolete] public int Foo() {...} or [Obsolete("This is a message describing why this method is obsolete")] public int Foo() {...} Note: The O in Obsolete is always capitalized.
<![if !supportLists]>30.<![endif]>lock(obj) { // code } translates to try { CriticalSection.Enter(obj); // code } finally { CriticalSection.Exit(obj); } <![if !supportLineBreakNewLine]> <![endif]>
<![if !supportLists]>32.<![endif]>using System.Runtime.InteropServices; <![if !supportLists]>33.<![endif]>class C <![if !supportLists]>34.<![endif]>{ <![if !supportLists]>35.<![endif]> [DllImport("user32.dll")] <![if !supportLists]>36.<![endif]> public static extern int MessageBoxA(int h, string m, string c, int type); <![if !supportLists]>37.<![endif]> public static int Main() <![if !supportLists]>38.<![endif]> { <![if !supportLists]>39.<![endif]> return MessageBoxA(0, "Hello World!", "Caption", 0); <![if !supportLists]>40.<![endif]> } <![if !supportLists]>41.<![endif]>} This example shows the minimum requirements for declaring a C# method that is implemented in a native DLL. The method C.MessageBoxA() is declared with the static and external modifiers, and has the DllImport attribute, which tells the compiler that the implementation comes from the user32.dll, using the default name of MessageBoxA. For more information, look at the Platform Invoke tutorial in the documentation.
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Good for preparation and general self-testing, but too specific for the actual job interview. This was sent in by a job applicant getting ready to step into the .NET field in India.
All methods marked with the DllImport attribute must be marked as public static extern.
- If you leave off the return type on a method declaration, the compiler thinks you are trying to declare a constructor. So if you are trying to declare a method that returns nothing, use void. The following is an example: // This results in a CS1006 error public static staticMethod (mainStatic obj) // This will work as wanted public static void staticMethod (mainStatic obj)
- The word checked is a keyword in C#.
- 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. Oneof 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.
- The following is a response from a developer on the C# compiler team: We get rid of unused locals (i.e., locals that are never read, even if assigned). We get rid of unreachable code. We get rid of try-catch with an empty try. We get rid of try-finally with an empty try. We get rid of try-finally with an empty finally. We optimize branches over branches: gotoif A, lab1 goto lab2: lab1: turns into: gotoif !A, lab2 lab1: We optimize branches to ret, branches to next instruction, and branches to branches.
- The syntax for calling another constructor is as follows: class B { B(int i) { } } class C : B { C() : base(5) // call base constructor B(5) { } C(int i) : this() // call C() { } publicstatic void Main() {} }
- Try using RegAsm.exe. Search MSDN on Assembly Registration Tool.
- From language spec: The list of similarities between classes and structs is as follows. Longstructs can implement interfaces and can have the same kinds of members as classes. Structs differ from classes in several important ways; however, structs are value types rather than reference types, and inheritance is not upported for structs. Struct values are stored on the stack or in-line. Careful programmers can sometimes enhance performance through judicious use of structs. For example, the use of a struct rather than a class for a Point can make a large difference in the number of memory allocations performed at runtime. The program below creates and initializes an array of 100 points. With Point implemented as a class, 101 separate objects are instantiated-one for the array and one each for the 100 elements.
<![if !supportLists]>13.<![endif]>switch(x) <![if !supportLists]>14.<![endif]>{ <![if !supportLists]>15.<![endif]> case 0: // do something <![if !supportLists]>16.<![endif]> case 1: // do something as continuation of case 0 <![if !supportLists]>17.<![endif]> default: // do something in common with <![if !supportLists]>18.<![endif]> //0, 1 and everything else <![if !supportLists]>19.<![endif]> break; <![if !supportLists]>20.<![endif]>} To achieve the same effect in C#, the code must be modified as shown below (notice how the control flows are explicit): class Test { public static void Main() { int x = 3; switch(x) { case 0: // do something goto case 1; case 1: // do something in common with 0 goto default; default: // do something in common with 0, 1, and anything else break; } } }
- Yes. The .NET class libraries provide support for regular expressions. Look at the System.Text.RegularExpressions namespace.
<![if !supportLists]>23.<![endif]>using System; <![if !supportLists]>24.<![endif]>using System.Threading; <![if !supportLists]>25.<![endif]>class ThreadTest <![if !supportLists]>26.<![endif]>{ <![if !supportLists]>27.<![endif]> public void runme() <![if !supportLists]>28.<![endif]> { <![if !supportLists]>29.<![endif]> Console.WriteLine("Runme Called"); <![if !supportLists]>30.<![endif]> } <![if !supportLists]>31.<![endif]> public static void Main(String[] args) <![if !supportLists]>32.<![endif]> { <![if !supportLists]>33.<![endif]> ThreadTest b = new ThreadTest(); <![if !supportLists]>34.<![endif]> Thread t = new Thread(new ThreadStart(b.runme)); <![if !supportLists]>35.<![endif]> t.Start(); <![if !supportLists]>36.<![endif]> } }
- Yes, you can use System.Environment.Exit(int exitCode) to exit the application or Application.Exit() if it’s a Windows Forms app.
- The easiest way is to use goto: <![if !supportLists]>40.<![endif]>using System; <![if !supportLists]>41.<![endif]>class BreakExample <![if !supportLists]>42.<![endif]>{ <![if !supportLists]>43.<![endif]> public static void Main(String[] args) { <![if !supportLists]>44.<![endif]> for(int i=0; i<3; i++) <![if !supportLists]>45.<![endif]> { <![if !supportLists]>46.<![endif]> Console.WriteLine("Pass {0}: ", i); <![if !supportLists]>47.<![endif]> for( int j=0 ; j<100 ; j++ ) <![if !supportLists]>48.<![endif]> { <![if !supportLists]>49.<![endif]> if ( j == 10) <![if !supportLists]>50.<![endif]> goto done; <![if !supportLists]>51.<![endif]> Console.WriteLine("{0} ", j); <![if !supportLists]>52.<![endif]> } <![if !supportLists]>53.<![endif]> Console.WriteLine("This will not print"); <![if !supportLists]>54.<![endif]> } <![if !supportLists]>55.<![endif]> done: <![if !supportLists]>56.<![endif]> Console.WriteLine("Loops complete."); <![if !supportLists]>57.<![endif]> } <![if !supportLists]>58.<![endif]>} <![if !supportLineBreakNewLine]> <![endif]>
- There is no way to restrict to a namespace. Namespaces are never units of protection. But if you’re using assemblies, you can use the ‘internal’ access modifier to restrict access to only within the assembly. |