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GetUnderlyingType Method

Enum.GetUnderlyingType Method

Returns the underlying type of the specified enumeration.

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

public static Type GetUnderlyingType(
	Type enumType


Type: System.Type

The enumeration whose underlying type will be retrieved.

Return Value

Type: System.Type
The underlying type of enumType.


enumType is null.


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)

   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

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

XNA Framework

Supported in: 3.0, 2.0, 1.0

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone Silverlight 8.1, Windows Phone Silverlight 8

Portable Class Library

Supported in: Portable Class Library
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