Enum.HasFlag(Enum) Метод

Определение

Пространство имен:

System

Сборка:

System.Runtime.dll

Исходный код:

Enum.cs

Определяет, установлены ли в текущем экземпляре одно или несколько битовых полей.

public:
 bool HasFlag(Enum ^ flag);

public bool HasFlag (Enum flag);

member this.HasFlag : Enum -> bool

Public Function HasFlag (flag As Enum) As Boolean

Параметры

flag

Enum

Значение перечисления.

Возвращаемое значение

Boolean

Значение true, если одно или несколько битовых полей, установленных в параметре flag, также установлены в текущем экземпляре; в противном случае — значение false.

Исключения

ArgumentException

flag — тип, отличный от текущего экземпляра.

Примеры

В следующем примере определяется DinnerItems перечисление, отражающее категории элементов, которые клиент может заказать в ресторане. В примере проверяется, заказал ли клиент как запись, так и напиток.

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

Комментарии

Метод HasFlag возвращает результат следующего логического выражения.

(thisInstance & flag) == flag

Если базовое значение равно flag нулю, метод возвращает true. Если такое поведение нежелательно, можно использовать Equals метод для проверки на равенство с нулевым значением и вызывать HasFlag только в том случае, если базовое значение flag параметра не равно нулю, как показано в следующем примере.

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.

Метод HasFlag предназначен для использования с типами перечисления, помеченными атрибутом FlagsAttribute , и может использоваться для определения того, заданы ли многобитовые поля. Для типов перечисления, которые не помечены атрибутом FlagsAttribute , вызовите Equals метод или CompareTo метод .

См. также раздел

• FlagsAttribute
• Equals(Object)