Q: Why don't nullable relational operators return “bool?” instead of “bool“? Nullable types are a new feature of C# 2.0 . When dealing with nullable types, if you write the following: int? i = 15; int? j = 16; the type...

Q: Why can't I do the following: namespace Bug { class Class1 { [ STAThread ] static void Main ( string [] args ) { for ( int i = 0; i < 100; i ++ ) { } int i = 0; } } } the compiler gives me an error...

Update: Named and optional (default) parameters are available starting from C# 4.0. For more information, see Named and Optional Arguments (C# Programming Guide) . Q: How do I write a method that accepts a variable number of parameters? ...

Q: In C++, it's possible to write a static method variable, and have a variable that can only be accessed from inside the method. C# doesn't provide this feature. Why? A: There are two reasons C# doesn't have this feature. First, it is possible...

Q: Why must attribute properties be read/write in C#? In the C# language, when you define an attribute class, you can define both constructor arguments and properties. For example: class MyAttribute: Attribute { string name; int number; public...

The code is trying to access a member of a reference type variable that is set to null . Given the following class, let's examine some code that could be in the Main method: using System; class Foo { static void Main() { // foo has not been...

You need to add a reference in your project to an assembly where that namespace is defined. If you are using VS.NET: 1. Right click on the References folder on your project. 2. Select Add Reference. 3. Select the .NET tab (or select the Browse button...

Delegates require information about the type that the method is associated with in order to make a call. In a single app-domain, this isn't a problem, because the server (the object firing the events) has access to the type information for the client...

If you set a property on a Windows Forms control which forces the creation of the control (e.g. the SelectedIndex property on the ComboBox class), the control (and perhaps the rest of the form) will not render with visual styles enabled. The resolution...

Q: Why aren't reference types polymorphic? A: Consider the following code: using System; class Dog { public string Name; } class Test { public static void Swap(ref object a, ref object b) { object temp; temp = a; a = b; b = temp; } public static...

The Equals method is just a virtual one defined in System.Object , and overridden by whichever classes choose to do so. The == operator is an operator which can be overloaded by classes, but which usually has identity behaviour. For reference...

Q: Should I assign null to my local variables after I use them? For example: string s = ...; Console.WriteLine(s); s = null; A: There is rarely a need to do this for local variables in C# The lifetime of variables is tracked by the JIT - it analyzes...

Q: Why do I need a null test before I invoke a delegate? A: If you have an event in a class, you need to add a null test before you call the delegate. Typically, you would write: if (Click != null ) Click(arg1, arg2); There is actually a possible...

Q: Why doesn't C# warn on unused methods? A: This is something that the C# compiler could do, subject to a few caveats: Virtual functions would have to be excluded Interface implementations wouldn have to be excluded You would get false...

When performing any action on a control which requires the updating of a user interface element (e.g. setting the Text property on almost any class derived from Control, updating the data source behind a DataGrid), these operations MUST take place on...

Q: Why can't I have static and instance methods with the same name? class Test { static void Process(); void Process(); void AmbiguousCaller() { Process(); } } there's no ambiguity, since the first can only be called through the type...

Refer to the System.Threading namespace on MSDN for full details. Meanwhile here is a quick taste. using System; using System.Threading; class ThreadTest { public void Runme() { Console.WriteLine( "Runme Called" ); Thread.Sleep(10000...

Q: How do C# generics compare to C++ templates? A: This is really a fairly complex topic. Anders has touched on it in an interview . I should state at the outset that the goals of generics are not the same as the goals of templates. There are...

Microsoft provides a very full language equivalents page which compares not only C# and VB.NET, but also other languages targeted at the .NET framework. It looks at the equivalent concepts, keywords, types, operators etc. A very valuable resource...

No, C# doesn't have an equivalent of VB.NET's MyClass keyword. If you want to guarantee not to call an overridden version of a method, you need to make it non-virtual in the first place. [Author: Jon Skeet]

To create delegate instances in C#, you just specify the delegate type, the method, and (if you want to create a delegate targetting a different instance or type from the current one) the target. For instance, each of these creates a ThreadStart delegate...

Use String.Substring . Assuming that x is a string of length at least n , to get the last n characters, you would use x.Substring(x.Length-n) . Note that the above assumes that the string is at least n characters long. For a more robust version...

Me in C# is this , and MyBase in C# is base . To access normal members, just use this.memberName or base.memberName . For information about chaining constructors together, see my article on constructors . [Author: Jon Skeet]

For reference types, the equivalent of VB's Nothing is C#'s null . For value types, it's the default value - 0 , false , etc. [Author: Jon Skeet]

If you need to tell C# that you want it to treat a literal as a particular type of number, you may do so by adding a number type suffix at the end of the literal you provide. For example: 1u; // An unsigned int 1l; // A signed long 1ul;...