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What is System.Void?
Why not System.Void?
I noticed that it is not allowed to use typeof(System.Void). But typeof(void) is allowed.
When you use typeof(System.String) or typeof(string) there is no difference.
Why is this the case?
This is because C# defines aliases to keep the original C flavor.
The .NET Framework uses specific naming conventions: for instance it states that a class name should start with a Capital. Therefore, String -- which is not a C# native type but a .NET class defined in the System namespace -- is actually called System.String, or String for short if you have a using System; in your file.
C# defines string as an alias of System.String so that code can look like it does in C and other C-based languages (C++, Java, ...). I think it's more readable. In the same fashion, int is the same as System.Int32.
void is not like string. In almost all cases where void is used in C#, it is given special treatment by the compiler, for example by not requiring a return statement in a void-"returning" method, and by not allowing a return statement with an expression with a "value" of type void. typeof(void) is one of the few cases where void is really treated as a regular type. And it works both ways: the compiler can assume that any type that is not void shouldn't get void's special treatment. Allowing other ways to spell void would make interpreting C# more complicated, and there is no reason why you would ever need it.
string is an alias of class System.String.
other list of aliases
thanks to Jon Skeet for this.
