Enum.HasFlag(Enum) 方法

定義

命名空間:

System

組件:

System.Runtime.dll

來源:

Enum.cs

判斷目前執行個體中是否設定一或多個位元欄位。

public:
 bool HasFlag(Enum ^ flag);

public bool HasFlag (Enum flag);

member this.HasFlag : Enum -> bool

Public Function HasFlag (flag As Enum) As Boolean

參數

flag

Enum

列舉值。

傳回

Boolean

如果目前執行個體中設定了 flag 中設定的一或多個位元欄位，則為 true；否則為 false。

例外狀況

ArgumentException

flag 的類型與目前執行個體的類型不同。

範例

下列範例會 DinnerItems 定義列舉，以反映客戶可以在餐廳中訂購的專案類別。 此範例會測試客戶是否已訂購專案和飲料。

using System;

[Flags] public enum DinnerItems {
   None = 0,
   Entree = 1,
   Appetizer = 2,
   Side = 4,
   Dessert = 8,
   Beverage = 16,
   BarBeverage = 32
}

public class Example
{
   public static void Main()
   {
      DinnerItems myOrder = DinnerItems.Appetizer | DinnerItems.Entree |
                            DinnerItems.Beverage | DinnerItems.Dessert;
      DinnerItems flagValue = DinnerItems.Entree | DinnerItems.Beverage;
      Console.WriteLine("{0} includes {1}: {2}",
                        myOrder, flagValue, myOrder.HasFlag(flagValue));
   }
}
// The example displays the following output:
//    Entree, Appetizer, Dessert, Beverage includes Entree, Beverage: True

open System

[<Flags>] 
type DinnerItems =
    | None = 0
    | Entree = 1
    | Appetizer = 2
    | Side = 4
    | Dessert = 8
    | Beverage = 16
    | BarBeverage = 32

let myOrder = 
    DinnerItems.Appetizer ||| DinnerItems.Entree ||| DinnerItems.Beverage ||| DinnerItems.Dessert
let flagValue = 
    DinnerItems.Entree ||| DinnerItems.Beverage
printfn $"{myOrder} includes {flagValue}: {myOrder.HasFlag flagValue}"
// The example displays the following output:
//    Entree, Appetizer, Dessert, Beverage includes Entree, Beverage: True

<Flags> Public Enum DinnerItems As Integer
   None = 0
   Entree = 1
   Appetizer = 2
   Side = 4
   Dessert = 8
   Beverage = 16 
   BarBeverage = 32
End Enum

Module Example
   Public Sub Main()
      Dim myOrder As DinnerItems = DinnerItems.Appetizer Or DinnerItems.Entree Or
                                   DinnerItems.Beverage Or DinnerItems.Dessert
      Dim flagValue As DinnerItems = DinnerItems.Entree Or DinnerItems.Beverage
      Console.WriteLine("{0} includes {1}: {2}", 
                        myOrder, flagValue, myOrder.HasFlag(flagValue))
   End Sub
End Module
' The example displays the following output:
'    Entree, Appetizer, Dessert, Beverage includes Entree, Beverage: True

備註

方法 HasFlag 會傳回下列布林運算式的結果。

(thisInstance & flag) == flag

如果 的基礎值為 flag 零，則方法會傳 true 回 。 如果不需要此行為，您可以使用 Equals 方法來測試是否與零相等，而且只有在 的基礎值為 flag 非零時才呼叫 HasFlag ，如下列範例所示。

using System;

[Flags] public enum Pets {
   None = 0,
   Dog = 1,
   Cat = 2,
   Bird = 4,
   Rabbit = 8,
   Other = 16
}

public class Example
{
   public static void Main()
   {
      Pets[] petsInFamilies = { Pets.None, Pets.Dog | Pets.Cat, Pets.Dog };
      int familiesWithoutPets = 0;
      int familiesWithDog = 0;

      foreach (var petsInFamily in petsInFamilies)
      {
         // Count families that have no pets.
         if (petsInFamily.Equals(Pets.None))
            familiesWithoutPets++;
         // Of families with pets, count families that have a dog.
         else if (petsInFamily.HasFlag(Pets.Dog))
            familiesWithDog++;
      }
      Console.WriteLine("{0} of {1} families in the sample have no pets.",
                        familiesWithoutPets, petsInFamilies.Length);
      Console.WriteLine("{0} of {1} families in the sample have a dog.",
                        familiesWithDog, petsInFamilies.Length);
   }
}
// The example displays the following output:
//       1 of 3 families in the sample have no pets.
//       2 of 3 families in the sample have a dog.

open System

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

let petsInFamilies = [| Pets.None; Pets.Dog ||| Pets.Cat; Pets.Dog |]
let mutable familiesWithoutPets = 0
let mutable familiesWithDog = 0

for petsInFamily in petsInFamilies do
    // Count families that have no pets.
    if petsInFamily.Equals Pets.None then
        familiesWithoutPets <- familiesWithoutPets + 1
    // Of families with pets, count families that have a dog.
    elif petsInFamily.HasFlag Pets.Dog then
        familiesWithDog <- familiesWithDog + 1

printfn $"{familiesWithoutPets} of {petsInFamilies.Length} families in the sample have no pets."
printfn $"{familiesWithDog} of {petsInFamilies} families in the sample have a dog."
// The example displays the following output:
//       1 of 3 families in the sample have no pets.
//       2 of 3 families in the sample have a dog.

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

Module Example
   Public Sub Main()
      Dim petsInFamilies() As Pets = { Pets.None, Pets.Dog Or Pets.Cat, Pets.Dog }
      Dim familiesWithoutPets As Integer
      Dim familiesWithDog As Integer
      
      For Each petsInFamily In petsInFamilies
         ' Count the number of families that have no pets.
         If petsInFamily.Equals(Pets.None) Then
            familiesWithoutPets += 1 
        ' Of families that have pets, count the number of families with a dog.
         Else If petsInFamily.HasFlag(Pets.Dog) Then
            familiesWithDog += 1
         End If
      Next
      Console.WriteLine("{0} of {1} families in the sample have no pets.", 
                        familiesWithoutPets, petsInFamilies.Length)   
      Console.WriteLine("{0} of {1} families in the sample have a dog.", 
                        familiesWithDog, petsInFamilies.Length)   
   End Sub
End Module
' The example displays the following output:
'       1 of 3 families in the sample have no pets.
'       2 of 3 families in the sample have a dog.

方法 HasFlag 的設計目的是要與以 FlagsAttribute 屬性標記的列舉型別搭配使用，而且可用來判斷是否已設定多個位欄位。 針對未以 屬性標記的 FlagsAttribute 列舉型別，請呼叫 Equals 方法或 CompareTo 方法。

另請參閱

• FlagsAttribute
• Equals(Object)