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.NET Framework 3.5
BitArray Class

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This page is specific to
Microsoft Visual Studio 2008/.NET Framework 3.5

Other versions are also available for the following:
.NET Framework Class Library
BitArray Class

Manages a compact array of bit values, which are represented as Booleans, where true indicates that the bit is on (1) and false indicates the bit is off (0).

Namespace:  System.Collections
Assembly:  mscorlib (in mscorlib.dll)
Visual Basic (Declaration)
<SerializableAttribute> _
<ComVisibleAttribute(True)> _
Public NotInheritable Class BitArray _
    Implements ICollection, IEnumerable, ICloneable
Visual Basic (Usage)
Dim instance As BitArray
C#
[SerializableAttribute]
[ComVisibleAttribute(true)]
public sealed class BitArray : ICollection, 
    IEnumerable, ICloneable
Visual C++
[SerializableAttribute]
[ComVisibleAttribute(true)]
public ref class BitArray sealed : ICollection, 
    IEnumerable, ICloneable
JScript
public final class BitArray implements ICollection, IEnumerable, ICloneable

The size of a BitArray is controlled by the client; indexing past the end of the BitArray throws an ArgumentException.

Elements in this collection can be accessed using an integer index. Indexes in this collection are zero-based.

The following code example shows how to create and initialize a BitArray and how to print out its values.

Visual Basic
Imports System
Imports System.Collections

Public Class SamplesBitArray

    Public Shared Sub Main()

        ' Creates and initializes several BitArrays.
        Dim myBA1 As New BitArray(5)

        Dim myBA2 As New BitArray(5, False)

        Dim myBytes() As Byte = {1, 2, 3, 4, 5}
        Dim myBA3 As New BitArray(myBytes)

        Dim myBools() As Boolean = {True, False, True, True, False}
        Dim myBA4 As New BitArray(myBools)

        Dim myInts() As Integer = {6, 7, 8, 9, 10}
        Dim myBA5 As New BitArray(myInts)

        ' Displays the properties and values of the BitArrays.
        Console.WriteLine("myBA1")
        Console.WriteLine("   Count:    {0}", myBA1.Count)
        Console.WriteLine("   Length:   {0}", myBA1.Length)
        Console.WriteLine("   Values:")
        PrintValues(myBA1, 8)

        Console.WriteLine("myBA2")
        Console.WriteLine("   Count:    {0}", myBA2.Count)
        Console.WriteLine("   Length:   {0}", myBA2.Length)
        Console.WriteLine("   Values:")
        PrintValues(myBA2, 8)

        Console.WriteLine("myBA3")
        Console.WriteLine("   Count:    {0}", myBA3.Count)
        Console.WriteLine("   Length:   {0}", myBA3.Length)
        Console.WriteLine("   Values:")
        PrintValues(myBA3, 8)

        Console.WriteLine("myBA4")
        Console.WriteLine("   Count:    {0}", myBA4.Count)
        Console.WriteLine("   Length:   {0}", myBA4.Length)
        Console.WriteLine("   Values:")
        PrintValues(myBA4, 8)

        Console.WriteLine("myBA5")
        Console.WriteLine("   Count:    {0}", myBA5.Count)
        Console.WriteLine("   Length:   {0}", myBA5.Length)
        Console.WriteLine("   Values:")
        PrintValues(myBA5, 8)

    End Sub 'Main

    Public Shared Sub PrintValues(myList As IEnumerable, myWidth As Integer)
        Dim i As Integer = myWidth
        Dim obj As [Object]
        For Each obj In  myList
            If i <= 0 Then
                i = myWidth
                Console.WriteLine()
            End If
            i -= 1
            Console.Write("{0,8}", obj)
        Next obj
        Console.WriteLine()
    End Sub 'PrintValues

End Class 'SamplesBitArray 


' This code produces the following output.
' 
' myBA1
'    Count:    5
'    Length:   5
'    Values:
'    False   False   False   False   False
' myBA2
'    Count:    5
'    Length:   5
'    Values:
'    False   False   False   False   False
' myBA3
'    Count:    40
'    Length:   40
'    Values:
'     True   False   False   False   False   False   False   False
'    False    True   False   False   False   False   False   False
'     True    True   False   False   False   False   False   False
'    False   False    True   False   False   False   False   False
'     True   False    True   False   False   False   False   False
' myBA4
'    Count:    5
'    Length:   5
'    Values:
'     True   False    True    True   False
' myBA5
'    Count:    160
'    Length:   160
'    Values:
'    False    True    True   False   False   False   False   False
'    False   False   False   False   False   False   False   False
'    False   False   False   False   False   False   False   False
'    False   False   False   False   False   False   False   False
'     True    True    True   False   False   False   False   False
'    False   False   False   False   False   False   False   False
'    False   False   False   False   False   False   False   False
'    False   False   False   False   False   False   False   False
'    False   False   False    True   False   False   False   False
'    False   False   False   False   False   False   False   False
'    False   False   False   False   False   False   False   False
'    False   False   False   False   False   False   False   False
'     True   False   False    True   False   False   False   False
'    False   False   False   False   False   False   False   False
'    False   False   False   False   False   False   False   False
'    False   False   False   False   False   False   False   False
'    False    True   False    True   False   False   False   False
'    False   False   False   False   False   False   False   False
'    False   False   False   False   False   False   False   False
'    False   False   False   False   False   False   False   False
C#
using System;
using System.Collections;
public class SamplesBitArray  {

   public static void Main()  {

      // Creates and initializes several BitArrays.
      BitArray myBA1 = new BitArray( 5 );

      BitArray myBA2 = new BitArray( 5, false );

      byte[] myBytes = new byte[5] { 1, 2, 3, 4, 5 };
      BitArray myBA3 = new BitArray( myBytes );

      bool[] myBools = new bool[5] { true, false, true, true, false };
      BitArray myBA4 = new BitArray( myBools );

      int[]  myInts  = new int[5] { 6, 7, 8, 9, 10 };
      BitArray myBA5 = new BitArray( myInts );

      // Displays the properties and values of the BitArrays.
      Console.WriteLine( "myBA1" );
      Console.WriteLine( "   Count:    {0}", myBA1.Count );
      Console.WriteLine( "   Length:   {0}", myBA1.Length );
      Console.WriteLine( "   Values:" );
      PrintValues( myBA1, 8 );

      Console.WriteLine( "myBA2" );
      Console.WriteLine( "   Count:    {0}", myBA2.Count );
      Console.WriteLine( "   Length:   {0}", myBA2.Length );
      Console.WriteLine( "   Values:" );
      PrintValues( myBA2, 8 );

      Console.WriteLine( "myBA3" );
      Console.WriteLine( "   Count:    {0}", myBA3.Count );
      Console.WriteLine( "   Length:   {0}", myBA3.Length );
      Console.WriteLine( "   Values:" );
      PrintValues( myBA3, 8 );

      Console.WriteLine( "myBA4" );
      Console.WriteLine( "   Count:    {0}", myBA4.Count );
      Console.WriteLine( "   Length:   {0}", myBA4.Length );
      Console.WriteLine( "   Values:" );
      PrintValues( myBA4, 8 );

      Console.WriteLine( "myBA5" );
      Console.WriteLine( "   Count:    {0}", myBA5.Count );
      Console.WriteLine( "   Length:   {0}", myBA5.Length );
      Console.WriteLine( "   Values:" );
      PrintValues( myBA5, 8 );
   }

   public static void PrintValues( IEnumerable myList, int myWidth )  {
      int i = myWidth;
      foreach ( Object obj in myList ) {
         if ( i <= 0 )  {
            i = myWidth;
            Console.WriteLine();
         }
         i--;
         Console.Write( "{0,8}", obj );
      }
      Console.WriteLine();
   }

}


/* 
This code produces the following output.

myBA1
   Count:    5
   Length:   5
   Values:
   False   False   False   False   False
myBA2
   Count:    5
   Length:   5
   Values:
   False   False   False   False   False
myBA3
   Count:    40
   Length:   40
   Values:
    True   False   False   False   False   False   False   False
   False    True   False   False   False   False   False   False
    True    True   False   False   False   False   False   False
   False   False    True   False   False   False   False   False
    True   False    True   False   False   False   False   False
myBA4
   Count:    5
   Length:   5
   Values:
    True   False    True    True   False
myBA5
   Count:    160
   Length:   160
   Values:
   False    True    True   False   False   False   False   False
   False   False   False   False   False   False   False   False
   False   False   False   False   False   False   False   False
   False   False   False   False   False   False   False   False
    True    True    True   False   False   False   False   False
   False   False   False   False   False   False   False   False
   False   False   False   False   False   False   False   False
   False   False   False   False   False   False   False   False
   False   False   False    True   False   False   False   False
   False   False   False   False   False   False   False   False
   False   False   False   False   False   False   False   False
   False   False   False   False   False   False   False   False
    True   False   False    True   False   False   False   False
   False   False   False   False   False   False   False   False
   False   False   False   False   False   False   False   False
   False   False   False   False   False   False   False   False
   False    True   False    True   False   False   False   False
   False   False   False   False   False   False   False   False
   False   False   False   False   False   False   False   False
   False   False   False   False   False   False   False   False
*/
Visual C++
using namespace System;
using namespace System::Collections;
void PrintValues( IEnumerable^ myList, int myWidth );
int main()
{

   // Creates and initializes several BitArrays.
   BitArray^ myBA1 = gcnew BitArray( 5 );
   BitArray^ myBA2 = gcnew BitArray( 5,false );
   array<Byte>^myBytes = {1,2,3,4,5};
   BitArray^ myBA3 = gcnew BitArray( myBytes );
   array<Boolean>^myBools = {true,false,true,true,false};
   BitArray^ myBA4 = gcnew BitArray( myBools );
   array<Int32>^myInts = {6,7,8,9,10};
   BitArray^ myBA5 = gcnew BitArray( myInts );

   // Displays the properties and values of the BitArrays.
   Console::WriteLine( "myBA1" );
   Console::WriteLine( "   Count:    {0}", myBA1->Count );
   Console::WriteLine( "   Length:   {0}", myBA1->Length );
   Console::WriteLine( "   Values:" );
   PrintValues( myBA1, 8 );
   Console::WriteLine( "myBA2" );
   Console::WriteLine( "   Count:    {0}", myBA2->Count );
   Console::WriteLine( "   Length:   {0}", myBA2->Length );
   Console::WriteLine( "   Values:" );
   PrintValues( myBA2, 8 );
   Console::WriteLine( "myBA3" );
   Console::WriteLine( "   Count:    {0}", myBA3->Count );
   Console::WriteLine( "   Length:   {0}", myBA3->Length );
   Console::WriteLine( "   Values:" );
   PrintValues( myBA3, 8 );
   Console::WriteLine( "myBA4" );
   Console::WriteLine( "   Count:    {0}", myBA4->Count );
   Console::WriteLine( "   Length:   {0}", myBA4->Length );
   Console::WriteLine( "   Values:" );
   PrintValues( myBA4, 8 );
   Console::WriteLine( "myBA5" );
   Console::WriteLine( "   Count:    {0}", myBA5->Count );
   Console::WriteLine( "   Length:   {0}", myBA5->Length );
   Console::WriteLine( "   Values:" );
   PrintValues( myBA5, 8 );
}

void PrintValues( IEnumerable^ myList, int myWidth )
{
   int i = myWidth;
   IEnumerator^ myEnum = myList->GetEnumerator();
   while ( myEnum->MoveNext() )
   {
      Object^ obj = safe_cast<Object^>(myEnum->Current);
      if ( i <= 0 )
      {
         i = myWidth;
         Console::WriteLine();
      }

      i--;
      Console::Write( "{0,8}", obj );
   }

   Console::WriteLine();
}

/* 
 This code produces the following output.

 myBA1
    Count:    5
    Length:   5
    Values:
    False   False   False   False   False
 myBA2
    Count:    5
    Length:   5
    Values:
    False   False   False   False   False
 myBA3
    Count:    40
    Length:   40
    Values:
     True   False   False   False   False   False   False   False
    False    True   False   False   False   False   False   False
     True    True   False   False   False   False   False   False
    False   False    True   False   False   False   False   False
     True   False    True   False   False   False   False   False
 myBA4
    Count:    5
    Length:   5
    Values:
     True   False    True    True   False
 myBA5
    Count:    160
    Length:   160
    Values:
    False    True    True   False   False   False   False   False
    False   False   False   False   False   False   False   False
    False   False   False   False   False   False   False   False
    False   False   False   False   False   False   False   False
     True    True    True   False   False   False   False   False
    False   False   False   False   False   False   False   False
    False   False   False   False   False   False   False   False
    False   False   False   False   False   False   False   False
    False   False   False    True   False   False   False   False
    False   False   False   False   False   False   False   False
    False   False   False   False   False   False   False   False
    False   False   False   False   False   False   False   False
     True   False   False    True   False   False   False   False
    False   False   False   False   False   False   False   False
    False   False   False   False   False   False   False   False
    False   False   False   False   False   False   False   False
    False    True   False    True   False   False   False   False
    False   False   False   False   False   False   False   False
    False   False   False   False   False   False   False   False
    False   False   False   False   False   False   False   False
 */
System..::.Object
  System.Collections..::.BitArray

Public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

This implementation does not provide a synchronized (thread safe) wrapper for a BitArray.

Enumerating through a collection is intrinsically not a thread-safe procedure. Even when a collection is synchronized, other threads can still modify the collection, which causes the enumerator to throw an exception. To guarantee thread safety during enumeration, you can either lock the collection during the entire enumeration or catch the exceptions resulting from changes made by other threads.

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 3.5, 2.0, 1.0

XNA Framework

Supported in: 3.0, 2.0, 1.0
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BitArray.Equals may be surprising      BHarris ... Dave Sexton   |   Edit   |   Show History
The BitArray class does not override the Equals method, resulting in identity comparison sementics: Two BitArrays with the same length and bit values may not be Equal!

Dave: This shouldn't be surprising since BitArray is a class, not a struct. This implies (correctly) that it uses reference-type semantics.
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