Enum.IsDefined Method (System)

.NET Framework Class Library

Enum..::.IsDefined Method

Updated: March 2009

Returns an indication whether a constant with a specified value exists in a specified enumeration.

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

Syntax

Visual Basic (Declaration)

<ComVisibleAttribute(True)> _
Public Shared Function IsDefined ( _
    enumType As Type, _
    value As Object _
) As Boolean

Visual Basic (Usage)

Dim enumType As Type
Dim value As Object
Dim returnValue As Boolean

returnValue = Enum.IsDefined(enumType, _
    value)

[ComVisibleAttribute(true)]
public static bool IsDefined(
    Type enumType,
    Object value
)

Visual C++

[ComVisibleAttribute(true)]
public:
static bool IsDefined(
    Type^ enumType, 
    Object^ value
)

JScript

public static function IsDefined(
    enumType : Type, 
    value : Object
) : boolean

Parameters

enumType: Type: System..::.Type
An enumeration type.

value: Type: System..::.Object
The value or name of a constant in enumType.

Return Value

Type: System..::.Boolean
true if a constant in enumType has a value equal to value; otherwise, false.

Exceptions

Exception	Condition
ArgumentNullException	enumType or value is nullNothingnullptra null reference (Nothing in Visual Basic).
ArgumentException	enumType is not an Enum. -or- The type of value is an enumeration, but it is not an enumeration of type enumType. -or- The type of value is not an underlying type of enumType.
InvalidOperationException	value is not type SByte, Int16, Int32, Int64, Byte, UInt16, UInt32, or UInt64, or String.

Exception

Condition

ArgumentNullException

enumType or value is nullNothingnullptra null reference (Nothing in Visual Basic).

ArgumentException

enumType is not an Enum.

-or-

The type of value is an enumeration, but it is not an enumeration of type enumType.

-or-

The type of value is not an underlying type of enumType.

InvalidOperationException

value is not type SByte, Int16, Int32, Int64, Byte, UInt16, UInt32, or UInt64, or String.

Remarks

The value parameter can be any of the following:

Any member of type enumType.
A variable whose value is an enumeration member of type enumType.
The string representation of the name of an enumeration member. The characters in the string must have the same case as the enumeration member name.
A value of the underlying type of enumType.

If the constants in enumType define a set of bit fields and value contains the values, names, or underlying values of multiple bit fields, the IsDefined method returns false. In other words, for enumerations that define a set of bit fields, the method is designed to determine only whether a single bit field belongs to the enumeration.

Examples

The following example defines an enumeration named PetType that consists of individual bit fields. It then calls the IsDefined method with possible underlying enumeration values, string names, and composite values that result from setting multiple bit fields.

Visual Basic

<Flags> Public Enum PetType As Integer
   None = 0
   Dog = 1
   Cat = 2
   Rodent = 4
   Bird = 8
   Reptile = 16
   Other = 32
End Enum

Module Example
   Public Sub Main()
      Dim value As Object

      ' Call IsDefined with underlying integral value of member.
      value = 1
      Console.WriteLine("{0}: {1}", value, [Enum].IsDefined(GetType(PetType), value))
      ' Call IsDefined with invalid underlying integral value.
      value = 64
      Console.WriteLine("{0}: {1}", value, [Enum].IsDefined(GetType(PetType), value))
      ' Call IsDefined with string containing member name.
      value = "Rodent"
      Console.WriteLine("{0}: {1}", value, [Enum].IsDefined(GetType(PetType), value))
      ' Call IsDefined with a variable of type PetType.
      value = PetType.Dog
      Console.WriteLine("{0}: {1}", value, [Enum].IsDefined(GetType(PetType), value))
      value = PetType.Dog Or PetType.Cat
      Console.WriteLine("{0}: {1}", value, [Enum].IsDefined(GetType(PetType), value))
      ' Call IsDefined with uppercase member name.      
      value = "None"
      Console.WriteLine("{0}: {1}", value, [Enum].IsDefined(GetType(PetType), value))
      value = "NONE"
      Console.WriteLine("{0}: {1}", value, [Enum].IsDefined(GetType(PetType), value))
      ' Call IsDefined with combined value
      value = PetType.Dog Or PetType.Bird
      Console.WriteLine("{0:D}: {1}", value, [Enum].IsDefined(GetType(PetType), value))
      value = value.ToString()
      Console.WriteLine("{0:D}: {1}", value, [Enum].IsDefined(GetType(PetType), value))
   End Sub
End Module
' The example displays the following output:
'       1: True
'       64: False 
'       Rodent: True
'       Dog: True
'       Dog, Cat: False
'       None: True
'       NONE: False
'       9: False
'       Dog, Bird: False

using System;

[Flags] public enum PetType
{
   None = 0, Dog = 1, Cat = 2, Rodent = 4, Bird = 8, Reptile = 16, Other = 32
};

public class Example
{
   public static void Main()
   {
      object value; 

      // Call IsDefined with underlying integral value of member.
      value = 1;
      Console.WriteLine("{0}: {1}", value, Enum.IsDefined(typeof(PetType), value));
      // Call IsDefined with invalid underlying integral value.
      value = 64;
      Console.WriteLine("{0}: {1}", value, Enum.IsDefined(typeof(PetType), value));
      // Call IsDefined with string containing member name.
      value = "Rodent";
      Console.WriteLine("{0}: {1}", value, Enum.IsDefined(typeof(PetType), value));
      // Call IsDefined with a variable of type PetType.
      value = PetType.Dog;
      Console.WriteLine("{0}: {1}", value, Enum.IsDefined(typeof(PetType), value));
      value = PetType.Dog | PetType.Cat;
      Console.WriteLine("{0}: {1}", value, Enum.IsDefined(typeof(PetType), value));
      // Call IsDefined with uppercase member name.      
      value = "None";
      Console.WriteLine("{0}: {1}", value, Enum.IsDefined(typeof(PetType), value));
      value = "NONE";
      Console.WriteLine("{0}: {1}", value, Enum.IsDefined(typeof(PetType), value));
      // Call IsDefined with combined value
      value = PetType.Dog | PetType.Bird;
      Console.WriteLine("{0:D}: {1}", value, Enum.IsDefined(typeof(PetType), value));
      value = value.ToString();
      Console.WriteLine("{0:D}: {1}", value, Enum.IsDefined(typeof(PetType), value));
   }
}
// The example displays the following output:
//       1: True
//       64: False
//       Rodent: True
//       Dog: True
//       Dog, Cat: False
//       None: True
//       NONE: False
//       9: False
//       Dog, Bird: False

Platforms

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.

Version Information