Enum.IsDefined Method
Returns an indication whether a constant with a specified value exists in a specified enumeration.
Namespace: System
Assembly: mscorlib (in mscorlib.dll)
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.Booleantrue if a constant in enumType has a value equal to value; otherwise, false.
| Exception | Condition |
|---|---|
| ArgumentNullException | enumType or value is null. |
| 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. |
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 determines only whether a single bit field belongs to the enumeration.
Notes to CallersIf 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. In the following example, a Pets enumeration is defined with the FlagsAttribute attribute. The IsDefined method returns false when you pass it an enumeration value that has two bit fields (Pets.Dog and Pets.Cat) set, and when you pass it the string representation of that enumeration value ("Dog, Cat").
using System; [Flags] public enum Pets { None = 0, Dog = 1, Cat = 2, Bird = 4, Rodent = 8, Other = 16 }; public class Example { public static void Main() { Pets value = Pets.Dog | Pets.Cat; Console.WriteLine("{0:D} Exists: {1}", value, Pets.IsDefined(typeof(Pets), value)); string name = value.ToString(); Console.WriteLine("{0} Exists: {1}", name, Pets.IsDefined(typeof(Pets), name)); } } // The example displays the following output: // 3 Exists: False // Dog, Cat Exists: False
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.
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
Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
