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GetUnderlyingType Method

Enum.GetUnderlyingType Method

Updated: August 2011

Returns the underlying type of the specified enumeration.

Namespace:  System
Assembly:  mscorlib (in mscorlib.dll)

[ComVisibleAttribute(true)]
public static Type GetUnderlyingType(
	Type enumType
)

Parameters

enumType
Type: System.Type

An enumeration type.

Return Value

Type: System.Type
The underlying Type of enumType.

ExceptionCondition
ArgumentNullException

enumType is null.

ArgumentException

enumType is not an Enum.

The Enum structure enables values to be represented as named constants. The data type of the enumeration's values is known as its underlying type. For example, the underlying type of the DayOfWeek enumeration, which consists of constants that represent each day of the week (DayOfWeek.Monday, DayOfWeek.Tuesday, and so on), is Int32.

The following example calls the GetUnderlyingType method to display the underlying type of some enumeration members.

using System;

public class Example
{
   public static void Main()
   {
      Enum[] enumValues = { ConsoleColor.Red, DayOfWeek.Monday, 
                            MidpointRounding.ToEven, PlatformID.Win32NT, 
                            DateTimeKind.Utc, StringComparison.Ordinal };
      Console.WriteLine("{0,-10} {1, 18}   {2,15}\n", 
                        "Member", "Enumeration", "Underlying Type");
      foreach (var enumValue in enumValues)
         DisplayEnumInfo(enumValue);
   }

   static void DisplayEnumInfo(Enum enumValue)
   {
      Type enumType = enumValue.GetType();
      Type underlyingType = Enum.GetUnderlyingType(enumType);
      Console.WriteLine("{0,-10} {1, 18}   {2,15}",
                        enumValue, enumType.Name, underlyingType.Name);   
   }
}
// The example displays the following output: 
//       Member            Enumeration   Underlying Type 
//        
//       Red              ConsoleColor             Int32 
//       Monday              DayOfWeek             Int32 
//       ToEven       MidpointRounding             Int32 
//       Win32NT            PlatformID             Int32 
//       Utc              DateTimeKind             Int32 
//       Ordinal      StringComparison             Int32

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 3.5, 2.0, 1.0

XNA Framework

Supported in: 3.0, 2.0, 1.0

Date

History

Reason

August 2011

Expanded the Remarks section and replaced the example.

Customer feedback.

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