FlagsAttribute Costruttore

public:
 FlagsAttribute();

public FlagsAttribute();

Public Sub New ()

Esempio

Nell'esempio seguente viene definita un'enumerazione PhoneService che rappresenta forme di comunicazione fornite da una società telefonica. Inizializza tre variabili che rappresentano il servizio fornito a tre famiglie diverse, e quindi indica quali famiglie non dispongono di servizi, quali famiglie hanno solo il servizio telefonico cellulare e quali famiglie dispongono sia di telefono cellulare che di servizio di linea fissa. Infine, chiama in modo implicito il Enum.ToString(String) metodo per visualizzare i tipi di servizio forniti a ogni famiglia.

using System;

[Flags]
public enum PhoneService
{
   None = 0,
   LandLine = 1,
   Cell = 2,
   Fax = 4,
   Internet = 8,
   Other = 16
}

public class Example
{
   public static void Main()
   {
      // Define three variables representing the types of phone service
      // in three households.
      var household1 = PhoneService.LandLine | PhoneService.Cell |
                       PhoneService.Internet;
      var household2 = PhoneService.None;
      var household3 = PhoneService.Cell | PhoneService.Internet;

      // Store the variables in an array for ease of access.
      PhoneService[] households = { household1, household2, household3 };

      // Which households have no service?
      for (int ctr = 0; ctr < households.Length; ctr++)
         Console.WriteLine("Household {0} has phone service: {1}",
                           ctr + 1,
                           households[ctr] == PhoneService.None ?
                               "No" : "Yes");
      Console.WriteLine();

      // Which households have cell phone service?
      for (int ctr = 0; ctr < households.Length; ctr++)
         Console.WriteLine("Household {0} has cell phone service: {1}",
                           ctr + 1,
                           (households[ctr] & PhoneService.Cell) == PhoneService.Cell ?
                              "Yes" : "No");
      Console.WriteLine();

      // Which households have cell phones and land lines?
      var cellAndLand = PhoneService.Cell | PhoneService.LandLine;
      for (int ctr = 0; ctr < households.Length; ctr++)
         Console.WriteLine("Household {0} has cell and land line service: {1}",
                           ctr + 1,
                           (households[ctr] & cellAndLand) == cellAndLand ?
                              "Yes" : "No");
      Console.WriteLine();

      // List all types of service of each household?//
      for (int ctr = 0; ctr < households.Length; ctr++)
         Console.WriteLine("Household {0} has: {1:G}",
                           ctr + 1, households[ctr]);
      Console.WriteLine();
   }
}
// The example displays the following output:
//    Household 1 has phone service: Yes
//    Household 2 has phone service: No
//    Household 3 has phone service: Yes
//
//    Household 1 has cell phone service: Yes
//    Household 2 has cell phone service: No
//    Household 3 has cell phone service: Yes
//
//    Household 1 has cell and land line service: Yes
//    Household 2 has cell and land line service: No
//    Household 3 has cell and land line service: No
//
//    Household 1 has: LandLine, Cell, Internet
//    Household 2 has: None
//    Household 3 has: Cell, Internet

<Flags()>
Public Enum PhoneService As Integer
   None = 0
   LandLine = 1
   Cell = 2
   Fax = 4
   Internet = 8
   Other = 16
End Enum

Module Example
   Public Sub Main()
      ' Define three variables representing the types of phone service
      ' in three households.
      Dim household1 As PhoneService = PhoneService.LandLine Or
                                       PhoneService.Cell Or
                                       PhoneService.Internet
      Dim household2 As PhoneService = PhoneService.None
      Dim household3 As PhoneService = PhoneService.Cell Or
                                       PhoneService.Internet

      ' Store the variables in an array for ease of access.
      Dim households() As PhoneService = { household1, household2,
                                           household3 }

      ' Which households have no service?
      For ctr As Integer = 0 To households.Length - 1
         Console.WriteLine("Household {0} has phone service: {1}",
                           ctr + 1,
                           If(households(ctr) = PhoneService.None,
                              "No", "Yes"))
      Next
      Console.WriteLine()
      
      ' Which households have cell phone service?
      For ctr As Integer = 0 To households.Length - 1
         Console.WriteLine("Household {0} has cell phone service: {1}",
                           ctr + 1,
                           If((households(ctr) And PhoneService.Cell) = PhoneService.Cell,
                              "Yes", "No"))
      Next
      Console.WriteLine()
      
      ' Which households have cell phones and land lines?
      Dim cellAndLand As PhoneService = PhoneService.Cell Or PhoneService.LandLine
      For ctr As Integer = 0 To households.Length - 1
         Console.WriteLine("Household {0} has cell and land line service: {1}",
                           ctr + 1,
                           If((households(ctr) And cellAndLand) = cellAndLand,
                              "Yes", "No"))
      Next
      Console.WriteLine()
      
      ' List all types of service of each household?'
      For ctr As Integer = 0 To households.Length - 1
         Console.WriteLine("Household {0} has: {1:G}",
                           ctr + 1, households(ctr))
      Next
      Console.WriteLine()
   End Sub
End Module
' The example displays the following output:
'    Household 1 has phone service: Yes
'    Household 2 has phone service: No
'    Household 3 has phone service: Yes
'
'    Household 1 has cell phone service: Yes
'    Household 2 has cell phone service: No
'    Household 3 has cell phone service: Yes
'
'    Household 1 has cell and land line service: Yes
'    Household 2 has cell and land line service: No
'    Household 3 has cell and land line service: No
'
'    Household 1 has: LandLine, Cell, Internet
'    Household 2 has: None
'    Household 3 has: Cell, Internet

Nell'esempio seguente viene mostrato l'uso dell'attributo FlagsAttribute e l'effetto sul metodo ToString dell'uso di FlagsAttribute in una dichiarazione Enum.

using System;

class Example
{
   // Define an Enum without FlagsAttribute.
   enum SingleHue : short
   {
      None = 0,
      Black = 1,
      Red = 2,
      Green = 4,
      Blue = 8
   };

   // Define an Enum with FlagsAttribute.
   [Flags]
   enum MultiHue : short
   {
      None = 0,
      Black = 1,
      Red = 2,
      Green = 4,
      Blue = 8
   };

   static void Main( )
   {
      // Display all possible combinations of values.
      Console.WriteLine(
           "All possible combinations of values without FlagsAttribute:");
      for(int val = 0; val <= 16; val++ )
         Console.WriteLine( "{0,3} - {1:G}", val, (SingleHue)val);

      // Display all combinations of values, and invalid values.
      Console.WriteLine(
           "\nAll possible combinations of values with FlagsAttribute:");
      for( int val = 0; val <= 16; val++ )
         Console.WriteLine( "{0,3} - {1:G}", val, (MultiHue)val);
   }
}
// The example displays the following output:
//       All possible combinations of values without FlagsAttribute:
//         0 - None
//         1 - Black
//         2 - Red
//         3 - 3
//         4 - Green
//         5 - 5
//         6 - 6
//         7 - 7
//         8 - Blue
//         9 - 9
//        10 - 10
//        11 - 11
//        12 - 12
//        13 - 13
//        14 - 14
//        15 - 15
//        16 - 16
//
//       All possible combinations of values with FlagsAttribute:
//         0 - None
//         1 - Black
//         2 - Red
//         3 - Black, Red
//         4 - Green
//         5 - Black, Green
//         6 - Red, Green
//         7 - Black, Red, Green
//         8 - Blue
//         9 - Black, Blue
//        10 - Red, Blue
//        11 - Black, Red, Blue
//        12 - Green, Blue
//        13 - Black, Green, Blue
//        14 - Red, Green, Blue
//        15 - Black, Red, Green, Blue
//        16 - 16

Module Example
   ' Define an Enum without FlagsAttribute.
   Enum SingleHue As Short
      None = 0
      Black = 1
      Red = 2
      Green = 4
      Blue = 8
   End Enum

   ' Define an Enum with FlagsAttribute.
   <Flags()> 
   Enum MultiHue As Short
      None = 0
      Black = 1
      Red = 2
      Green = 4
      Blue = 8
   End Enum

   Sub Main()
      ' Display all possible combinations of values.
      Console.WriteLine(
           "All possible combinations of values without FlagsAttribute:")
      For val As Integer = 0 To 16
         Console.WriteLine("{0,3} - {1:G}", val, CType(val, SingleHue))
     Next 
     Console.WriteLine()
     
     ' Display all combinations of values, and invalid values.
     Console.WriteLine( 
          "All possible combinations of values with FlagsAttribute:")
     For val As Integer = 0 To 16
        Console.WriteLine( "{0,3} - {1:G}", val, CType(val, MultiHue))
     Next 
   End Sub 
End Module 
' The example displays the following output:
'       All possible combinations of values without FlagsAttribute:
'         0 - None
'         1 - Black
'         2 - Red
'         3 - 3
'         4 - Green
'         5 - 5
'         6 - 6
'         7 - 7
'         8 - Blue
'         9 - 9
'        10 - 10
'        11 - 11
'        12 - 12
'        13 - 13
'        14 - 14
'        15 - 15
'        16 - 16
'       
'       All possible combinations of values with FlagsAttribute:
'         0 - None
'         1 - Black
'         2 - Red
'         3 - Black, Red
'         4 - Green
'         5 - Black, Green
'         6 - Red, Green
'         7 - Black, Red, Green
'         8 - Blue
'         9 - Black, Blue
'        10 - Red, Blue
'        11 - Black, Red, Blue
'        12 - Green, Blue
'        13 - Black, Green, Blue
'        14 - Red, Green, Blue
'        15 - Black, Red, Green, Blue
'        16 - 16