Enum.HasFlag(Enum) Method
Definition
Important
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Determines whether one or more bit fields are set in the current instance.
public:
bool HasFlag(Enum ^ flag);public bool HasFlag (Enum flag);member this.HasFlag : Enum -> boolPublic Function HasFlag (flag As Enum) As BooleanParameters
- flag
- Enum
An enumeration value.
Returns
true if the bit field or bit fields that are set in flag are also set in the current instance; otherwise, false.
Exceptions
flag is a different type than the current instance.
Examples
The following example defines an DinnerItems enumeration that reflects categories of items that a customer can order in a restaurant. The example tests whether the customer has ordered both an entrée and a beverage.
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
Remarks
The HasFlag method returns the result of the following Boolean expression.
(thisInstance & flag) == flag
If the underlying value of flag is zero, the method returns true. If this behavior is not desirable, you can use the Equals method to test for equality with zero and call HasFlag only if the underlying value of flag is non-zero, as the following example illustrates.
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.
The HasFlag method is designed to be used with enumeration types that are marked with the FlagsAttribute attribute and can be used to determine whether multiple bit fields are set. For enumeration types that are not marked with the FlagsAttribute attribute, call either the Equals method or the CompareTo method.
