typeof (C# Reference)

Switch View

typeof

Collapse All

Language Filter

This page is specific to

Microsoft Visual Studio 2008/.NET Framework 3.5

Other versions are also available for the following:

C# Language Reference

typeof (C# Reference)

Used to obtain the System.Type object for a type. A typeof expression takes the following form:

System.Type type = typeof(int);

Remarks

To obtain the run-time type of an expression, you can use the .NET Framework method GetType, as in the following example:

int i = 0;
System.Type type = i.GetType();

The typeof operator cannot be overloaded.

The typeof operator can also be used on open generic types. Types with more than one type parameter must have the appropriate number of commas in the specification. The following example shows how to determine whether the return type of a method is a generic IEnumerable<(Of <(T>)>). Assume that method is an instance of a MethodInfo type:

string s = method.ReturnType.GetInterface
    (typeof(System.Collections.Generic.IEnumerable<>).FullName);

Example

public class ExampleClass
{
    public int sampleMember;
    public void SampleMethod() { }

    static void Main()
    {
        Type t = typeof(ExampleClass);
        // Alternatively, you could use
        // ExampleClass obj = new ExampleClass();
        // Type t = obj.GetType();

        Console.WriteLine("Methods:");
        System.Reflection.MethodInfo[] methodInfo = t.GetMethods();

        foreach (System.Reflection.MethodInfo mInfo in methodInfo)
            Console.WriteLine(mInfo.ToString());

        Console.WriteLine("Members:");
        System.Reflection.MemberInfo[] memberInfo = t.GetMembers();

        foreach (System.Reflection.MemberInfo mInfo in memberInfo)
            Console.WriteLine(mInfo.ToString());
    }
}
/*
 Output:
    Methods:
    Void SampleMethod()
    System.String ToString()
    Boolean Equals(System.Object)
    Int32 GetHashCode()
    System.Type GetType()
    Members:
    Void SampleMethod()
    System.String ToString()
    Boolean Equals(System.Object)
    Int32 GetHashCode()
    System.Type GetType()
    Void .ctor()
    Int32 sampleMember
*/

This sample uses the GetType method to determine the type that is used to contain the result of a numeric calculation. This depends on the storage requirements of the resulting number.

class GetTypeTest
{
    static void Main()
    {
        int radius = 3;
        Console.WriteLine("Area = {0}", radius * radius * Math.PI);
        Console.WriteLine("The type is {0}",
                          (radius * radius * Math.PI).GetType()
        );
    }
}
/*
Output:
Area = 28.2743338823081
The type is System.Double
*/

C# Language Specification

For more information, see the following sections in the C# Language Specification:

7.5.11 The typeof operator

Tags

: Add a tag

Flag as ContentBug

GetType Example - Using PowerShell

Thomas Lee | Edit | Show History

<#
.SYNOPSIS
    This script displays the value, and type, of an expression.
.DESCRIPTION
    This script is a rewrite of the second example on this page, The 
    script illustrates how to use the GetType method to return
    the type that results from a calculation. in this case, two 
    multiplying two int32 with the Pi field results in a System.Double.
.NOTES
    File Name  : get-typetest.ps1
    Author     : Thomas Lee - tfl@psp.co.uk
    Requires   : PowerShell V2 CTP3
.LINK
    This script posted to:
http://pshscripts.blogspot.com/2009/06/get-typetestps1.html
    MSDN Sample posted at:
http://msdn.microsoft.com/en-us/library/58918ffs.aspx
.EXAMPLE
    PSH [C:\foo]: .\get-typetest.PS1
    The type of $Radius is       : System.Int32
    Area =                         28.2743338823081
    The type is the expression is: System.Double
#>

##
# Start of Script
##

# Set and display type of radius
[int] $radius = 3
"The type of `$Radius is       : {0}" -f $radius.GetType()

# Display Area, and the type of an expression.
"Area                           {0}" -f ($radius * $radius * [System.Math]::PI)
"The type is the expression is: {0}" -f ($radius * $radius * [System.Math]::PI).GetType()
# End of Script

Concepts

Reference

Other Resources