Enum.IsDefined Method
Microsoft Silverlight will reach end of support after October 2021. Learn more.
Returns an indication whether a constant with a specified value exists in a specified enumeration.
Namespace: System
Assembly: mscorlib (in mscorlib.dll)
Syntax
'Declaration
<ComVisibleAttribute(True)> _
Public Shared Function IsDefined ( _
enumType As Type, _
value As Object _
) As Boolean
[ComVisibleAttribute(true)]
public static bool IsDefined(
Type enumType,
Object value
)
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 nulla null reference (Nothing in Visual Basic). |
| ArgumentException | enumType is not an Enum. -or- The type of value is not an 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.
Notes to Callers
If enumType is an enumeration that is defined by using the FlagsAttribute attribute, the method returns false if multiple bit fields in value are set but value does not correspond to a composite enumeration value, or if value is a string concatenation of the names of multiple bit flags.
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.
<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 Demo(outputBlock As System.Windows.Controls.TextBlock)
Dim value As Object
' Call IsDefined with underlying integral value of member.
value = 1
outputBlock.Text += String.Format("{0}: {1}", _
value, [Enum].IsDefined(GetType(PetType), value)) + vbCrLf
' Call IsDefined with invalid underlying integral value.
value = 64
outputBlock.Text += String.Format("{0}: {1}", _
value, [Enum].IsDefined(GetType(PetType), value)) + vbCrLf
' Call IsDefined with string containing member name.
value = "Rodent"
outputBlock.Text += String.Format("{0}: {1}", _
value, [Enum].IsDefined(GetType(PetType), value)) + vbCrLf
' Call IsDefined with a variable of type PetType.
value = PetType.Dog
outputBlock.Text += String.Format("{0}: {1}", _
value, [Enum].IsDefined(GetType(PetType), value)) + vbCrLf
value = PetType.Dog Or PetType.Cat
outputBlock.Text += String.Format("{0}: {1}", _
value, [Enum].IsDefined(GetType(PetType), value)) + vbCrLf
' Call IsDefined with uppercase member name.
value = "None"
outputBlock.Text += String.Format("{0}: {1}", _
value, [Enum].IsDefined(GetType(PetType), value)) + vbCrLf
value = "NONE"
outputBlock.Text += String.Format("{0}: {1}", _
value, [Enum].IsDefined(GetType(PetType), value)) + vbCrLf
' Call IsDefined with combined value
value = PetType.Dog Or PetType.Bird
outputBlock.Text += String.Format("{0:D}: {1}", _
value, [Enum].IsDefined(GetType(PetType), value)) + vbCrLf
value = value.ToString()
outputBlock.Text += String.Format("{0:D}: {1}", _
value, [Enum].IsDefined(GetType(PetType), value)) + vbCrLf
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 Demo(System.Windows.Controls.TextBlock outputBlock)
{
object value;
// Call IsDefined with underlying integral value of member.
value = 1;
outputBlock.Text += String.Format("{0}: {1}\n",
value, Enum.IsDefined(typeof(PetType), value));
// Call IsDefined with invalid underlying integral value.
value = 64;
outputBlock.Text += String.Format("{0}: {1}\n",
value, Enum.IsDefined(typeof(PetType), value));
// Call IsDefined with string containing member name.
value = "Rodent";
outputBlock.Text += String.Format("{0}: {1}\n",
value, Enum.IsDefined(typeof(PetType), value));
// Call IsDefined with a variable of type PetType.
value = PetType.Dog;
outputBlock.Text += String.Format("{0}: {1}\n",
value, Enum.IsDefined(typeof(PetType), value));
value = PetType.Dog | PetType.Cat;
outputBlock.Text += String.Format("{0}: {1}\n",
value, Enum.IsDefined(typeof(PetType), value));
// Call IsDefined with uppercase member name.
value = "None";
outputBlock.Text += String.Format("{0}: {1}\n",
value, Enum.IsDefined(typeof(PetType), value));
value = "NONE";
outputBlock.Text += String.Format("{0}: {1}\n",
value, Enum.IsDefined(typeof(PetType), value));
// Call IsDefined with combined value
value = PetType.Dog | PetType.Bird;
outputBlock.Text += String.Format("{0:D}: {1}\n",
value, Enum.IsDefined(typeof(PetType), value));
value = value.ToString();
outputBlock.Text += String.Format("{0:D}: {1}\n",
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
Version Information
Silverlight
Supported in: 5, 4, 3
Silverlight for Windows Phone
Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0
XNA Framework
Supported in: Xbox 360, Windows Phone OS 7.0
Platforms
For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.