Enum.IsDefined 方法

  • 参考

定义

命名空间:
System
程序集:
System.Runtime.dll
程序集:
mscorlib.dll
程序集:
netstandard.dll

重载

IsDefined(Type, Object)

返回一个布尔值，该值指示给定的整数值或其名称字符串是否存在于指定的枚举中。
IsDefined<TEnum>(TEnum)

返回一个布尔值，该值指示给定的整数值或其名称字符串是否存在于指定的枚举中。

IsDefined(Type, Object)

Source:
Enum.cs
Source:
Enum.cs
Source:
Enum.cs

返回一个布尔值，该值指示给定的整数值或其名称字符串是否存在于指定的枚举中。

public:
 static bool IsDefined(Type ^ enumType, System::Object ^ value);
public static bool IsDefined (Type enumType, object value);
[System.Runtime.InteropServices.ComVisible(true)]
public static bool IsDefined (Type enumType, object value);
static member IsDefined : Type * obj -> bool
[<System.Runtime.InteropServices.ComVisible(true)>]
static member IsDefined : Type * obj -> bool
Public Shared Function IsDefined (enumType As Type, value As Object) As Boolean

参数

enumType
Type

枚举类型。

value
Object

enumType 中的常量的值或名称。

返回

Boolean

如果 enumType 中的某个常量的值等于 value，则为 true；否则为 false。

属性
ComVisibleAttribute

例外

ArgumentNullException

enumType 或 value 为 null。

ArgumentException

enumType 不是 Enum。

- 或 -

value 的类型是枚举，但它不是类型 enumType 的枚举。

- 或 -

value 的类型不是 enumType 的基础类型。

InvalidOperationException

value 的类型不为 SByte、Int16、Int32、Int64、Byte、UInt16、UInt32UInt64 或 String。

示例

以下示例定义一个名为 PetType 的枚举，该枚举由单个位字段组成。 然后， IsDefined 它使用可能的基础枚举值、字符串名称和设置多个位字段产生的复合值调用 方法。

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

open System

[<Flags>]
type PetType =
    | None = 0
    | Dog = 1
    | Cat = 2
    | Rodent = 4
    | Bird = 8
    | Reptile = 16
    | Other = 32

[<EntryPoint>]
let main _ =
    // Call IsDefined with underlying integral value of member.
    let value = 1
    printfn $"{value}: {Enum.IsDefined(typeof<PetType>, value)}"
    // Call IsDefined with invalid underlying integral value.
    let value = 64
    printfn $"{value}: {Enum.IsDefined(typeof<PetType>, value)}"
    // Call IsDefined with string containing member name.
    let value = "Rodent"
    printfn $"{value}: {Enum.IsDefined(typeof<PetType>, value)}"
    // Call IsDefined with a variable of type PetType.
    let value = PetType.Dog
    printfn $"{value}: {Enum.IsDefined(typeof<PetType>, value)}"
    let value = PetType.Dog ||| PetType.Cat
    printfn $"{value}: {Enum.IsDefined(typeof<PetType>, value)}"
    // Call IsDefined with uppercase member name.
    let value = "None"
    printfn $"{value}: {Enum.IsDefined(typeof<PetType>, value)}"
    let value = "NONE"
    printfn $"{value}: {Enum.IsDefined(typeof<PetType>, value)}"
    // Call IsDefined with combined value
    let value = PetType.Dog ||| PetType.Bird
    printfn $"{value:D}: {Enum.IsDefined(typeof<PetType>, value)}"
    let value = value.ToString()
    printfn $"{value:D}: {Enum.IsDefined(typeof<PetType>, value)}"
    0
// 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

<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

注解

参数 value 可以是以下任一项：

  • 类型 enumType的任何成员。

  • 一个变量，其值为 类型的 enumType枚举成员。

  • 枚举成员名称的字符串表示形式。 字符串中的字符必须与枚举成员名称具有相同大小写。

  • 基础类型的 enumType值。

如果 中的 enumType 常量定义一组位字段并 value 包含多个位字段的值、名称或基础值，则 IsDefined 该方法返回 false。 换句话说，对于定义一组位字段的枚举， 方法仅确定单个位字段是否属于枚举。 若要确定是否在用 FlagsAttribute 属性标记的枚举类型中设置多个位字段，可以调用 HasFlag 方法。

调用方说明

如果 enumType 是使用 FlagsAttribute 特性定义的枚举，则如果 中的多个位字段value已设置但value与复合枚举值不对应，或者如果 value 是多个位标志名称的字符串串联，则方法返回 false 。 在下面的示例中， Pets 枚举是使用 FlagsAttribute 属性定义的。 向它传递具有两个位字段 (Pets.Dog和Pets.Cat) 集的枚举值时，该方法IsDefined(Type, Object)返回 false ;传递它时，该枚举值的字符串表示形式 (“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

open System

[<Flags>]
type Pets =
    | None = 0
    | Dog = 1
    | Cat = 2
    | Bird = 4
    | Rodent = 8
    | Other = 16

let value = Pets.Dog ||| Pets.Cat
printfn $"{value:D} Exists: {Pets.IsDefined(typeof<Pets>, value)}"
let name = string value
printfn $"{name} Exists: {Pets.IsDefined(typeof<Pets>, name)}"
// The example displays the following output:
//       3 Exists: False
//       Dog, Cat Exists: False

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

Module Example
   Public Sub Main()
      Dim value As Pets = Pets.Dog Or Pets.Cat
      Console.WriteLine("{0:D} Exists: {1}", 
                        value, Pets.IsDefined(GetType(Pets), value))
      Dim name As String = value.ToString()
      Console.WriteLine("{0} Exists: {1}", 
                        name, Pets.IsDefined(GetType(Pets), name))
   End Sub
End Module
' The example displays the following output:
'       3 Exists: False
'       Dog, Cat Exists: False

可以通过调用 HasFlag(Enum) 方法来确定是否设置多个位字段。

另请参阅

适用于

IsDefined<TEnum>(TEnum)

Source:
Enum.cs
Source:
Enum.cs
Source:
Enum.cs

返回一个布尔值，该值指示给定的整数值或其名称字符串是否存在于指定的枚举中。

public:
generic <typename TEnum>
 where TEnum : value class static bool IsDefined(TEnum value);
public static bool IsDefined<TEnum> (TEnum value) where TEnum : struct;
static member IsDefined : 'Enum -> bool (requires 'Enum : struct)
Public Shared Function IsDefined(Of TEnum As Structure) (value As TEnum) As Boolean

类型参数

TEnum

枚举的类型。

参数

value
TEnum

TEnum 中的常量的值或名称。

返回

Boolean

如果给定整数值或其名称字符串存在于指定的枚举中，则为 true，否则为 false。

适用于