C# Programming/Keywords/typeof

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The typeof keyword returns an instance of the System.Type class when passed a name of a class. It is similar to the sizeof|sizeof keyword in that it returns a value instead of starting a section (block) of code (see if, try, while).

An example:

using System;
 
namespace MyNamespace
{
    class MyClass
    {
        static void Main(string[] args)
        {
            Type t = typeof(int);
            Console.Out.WriteLine(t.ToString());
            Console.In.Read();
        }
    }
}

The output will be:

System.Int32

It should be noted that unlike sizeof, only class names themselves and not variables can be passed to typeof as shown here:

using System;

namespace MyNamespace
{
    class MyClass2
    {
        static void Main(string[] args)
        {
            char ch;
            
            // This line will cause compilation to fail
            Type t = typeof(ch);
            Console.Out.WriteLine(t.ToString());
            Console.In.Read();
        }
    }
}

Sometimes, classes will include their own GetType() method that will be similar, if not identical, to typeof.



C# Keywords
abstract as base bool break
byte case catch char checked
class const continue decimal default
delegate do double else enum
event explicit extern false finally
fixed float for foreach
goto if implicit in int
interface internal is lock long
namespace new null object operator
out override params private protected
public readonly ref return sbyte
sealed short sizeof stackalloc
static string struct switch this
throw true try typeof uint
ulong unchecked unsafe ushort using
var virtual void volatile while
Special C# Identifiers
add alias get global partial
remove set value where yield