Enum.IsDefined 方法

定义

命名空间:: System

程序集:: mscorlib.dll, System.Runtime.dll

程序集:: netstandard.dll, System.Runtime.dll

程序集:: System.Runtime.dll

程序集:: mscorlib.dll

程序集:: netstandard.dll

重要

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重载

名称	说明
IsDefined(Type, Object)	返回一个布尔值，指示给定的整数值或其名称是否在指定的枚举中存在。
IsDefined<TEnum>(TEnum)	返回一个布尔值，指示给定整数值或其名称是否存在于指定的枚举中。

IsDefined(Type, Object)

Source:: Enum.cs

Source:: Enum.cs

Source:: Enum.cs

Source:: Enum.cs

Source:: Enum.cs

返回一个布尔值，指示给定的整数值或其名称是否在指定的枚举中存在。

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

中的 enumType常量的值或名称。

Boolean

true 如果常量中的 enumType 常量的值等于 value;否则为 false。

属性: ComVisibleAttribute

例外

ArgumentNullException

enumType 或 value 为 null.

ArgumentException

enumType不是 .Enum

-或-

value类型为枚举，但它不是类型的enumType枚举。

-或-

value类型不是基础类型的 enumType。

InvalidOperationException

value不是类型SByte、、、Int16、Int32、Int64 Byte、或UInt16 UInt32。UInt64 String

示例

以下示例定义一个名为由单个位字段组成的枚举 PetType 。然后，它使用可能的基础枚举值、字符串名称和复合值调用 IsDefined 该方法，这些值由设置多个位字段产生。

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

该 value 参数可以是以下任一参数：

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。

enumType如果定义一组位字段并value包含多个位字段的值、名称或基础值，该方法IsDefined将false返回。换句话说，对于定义一组位字段的枚举，该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 特性标记的枚举类型中设置多个位字段，可以调用该方法 HasFlag 。

调用方说明

如果 enumType 为使用 FlagsAttribute 特性定义的枚举，则该方法返回 false 如果设置了多个位字段 value ，但 value 与复合枚举值不对应，或者是否 value 是多个位标志名称的字符串串联。在以下示例中， Pets 使用特性定义 FlagsAttribute 枚举。此方法 IsDefined(Type, Object) 在 false 传递时返回一个枚举值，该值设置了两个位字段（Pets.Dog 和 Pets.Cat），并在传递该枚举值的字符串表示形式（“Dog，Cat”）时返回。

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) 该方法来确定是否设置了多个位字段。

另请参阅

适用于

IsDefined<TEnum>(TEnum)

Source:: Enum.cs

Source:: Enum.cs

Source:: Enum.cs

Source:: Enum.cs

Source:: Enum.cs

返回一个布尔值，指示给定整数值或其名称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

中的 TEnum常量的值或名称。

Boolean

true 如果给定整数值或其名称作为字符串存在，则为指定枚举中; false 否则。

适用于

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