.NET Framework Class Library
BinaryWriter Class

Updated: November 2007

Writes primitive types in binary to a stream and supports writing strings in a specific encoding.

Namespace:  System.IO
Assembly:  mscorlib (in mscorlib.dll)

Visual Basic (Declaration)
<SerializableAttribute> _
<ComVisibleAttribute(True)> _
Public Class BinaryWriter _
    Implements IDisposable
Visual Basic (Usage)
Dim instance As BinaryWriter
C#
[SerializableAttribute]
[ComVisibleAttribute(true)]
public class BinaryWriter : IDisposable
Visual C++
[SerializableAttribute]
[ComVisibleAttribute(true)]
public ref class BinaryWriter : IDisposable
J#
/** @attribute SerializableAttribute */ 
/** @attribute ComVisibleAttribute(true) */
public class BinaryWriter implements IDisposable
JScript
public class BinaryWriter implements IDisposable

A derived class can override the methods of this class to give unique character encodings.

For a list of common I/O tasks, see Common I/O Tasks.

The following code example demonstrates how to store and retrieve application settings in a file.

Visual Basic
Imports Microsoft.VisualBasic
Imports System
Imports System.IO
Imports System.Security.Permissions

Public Class Test

    Shared Sub Main()

        ' Load application settings.
        Dim appSettings As New AppSettings()
        Console.WriteLine("App settings." & vbcrLf & "Aspect " & _
            "Ratio: {0}, Lookup directory: {1}," & vbcrLf & "Auto " & _
            "save time: {2} minutes, Show status bar: {3}" & vbCrLf, _
            New Object(3){appSettings.AspectRatio.ToString(), _
            appSettings.LookupDir, _
            appSettings.AutoSaveTime.ToString(), _
            appSettings.ShowStatusBar.ToString()})

        ' Change the settings.
        appSettings.AspectRatio   = 1.250
        appSettings.LookupDir     = "C:\Temp"
        appSettings.AutoSaveTime  = 10
        appSettings.ShowStatusBar = True

        ' Save the new settings.
        appSettings.Close()

    End Sub
End Class

' Store and retrieve application settings.
Public Class AppSettings

    Const fileName As String = "AppSettings#@@#.dat"
    Dim aspRatio As Single
    Dim lkupDir As String
    Dim saveTime As Integer
    Dim statusBar As Boolean

    Property AspectRatio As Single
        Get
            Return aspRatio
        End Get
        Set
            aspRatio = Value
        End Set
    End Property

    Property LookupDir As String
        Get
            Return lkupDir
        End Get
        Set
            lkupDir = Value
        End Set
    End Property

    Property AutoSaveTime As Integer
        Get
            Return saveTime
        End Get
        Set
            saveTime = Value
        End Set
    End Property

    Property ShowStatusBar As Boolean
        Get
            Return statusBar
        End Get
        Set
            statusBar = Value
        End Set
    End Property

    Sub New()

        ' Create default application settings.
        aspRatio   = 1.3333
        lkupDir     = "C:\AppDirectory"
        saveTime  = 30
        statusBar = False

        If File.Exists(fileName) Then
            Dim binReader As New BinaryReader( _
                File.Open(fileName, FileMode.Open))
            Try

                ' If the file is not empty,
                ' read the application settings.
                ' Read 4 bytes into a buffer to 
                ' determine if the file is empty.
                Dim testArray As Byte() = {0,0,0,0}
                Dim count As Integer = binReader.Read(testArray, 0, 3)

                If count <> 0 Then
                    aspRatio   = binReader.ReadSingle()
                    lkupDir     = binReader.ReadString()
                    saveTime  = binReader.ReadInt32()
                    statusBar = binReader.ReadBoolean()
                    Return
                End If

            ' If the end of the stream is reached before reading
            ' the four data values, ignore the error and use the
            ' default settings for the remaining values.
            Catch ex As EndOfStreamException
                Console.WriteLine("{0} caught and ignored. " & _ 
                    "Using default values.", ex.GetType().Name)
            Finally
                binReader.Close()
            End Try
        End If

    End Sub

    ' Create a file and store the application settings.
    Sub Close()
        Dim binWriter As New BinaryWriter( _
            File.Open(fileName, FileMode.Create))
        Try
            binWriter.Write(aspRatio)
            binWriter.Write(lkupDir)
            binWriter.Write(saveTime)
            binWriter.Write(statusBar)
        Finally
            binWriter.Close()
        End Try
    End Sub

End Class

C#
using System;
using System.IO;
using System.Security.Permissions;

class Test
{
    static void Main()
    {
        // Load application settings.
        AppSettings appSettings = new AppSettings();
        Console.WriteLine("App settings.\nAspect Ratio: {0}, " +
            "Lookup directory: {1},\nAuto save time: {2} minutes, " +
            "Show status bar: {3}\n",
            new Object[4]{appSettings.AspectRatio.ToString(),
            appSettings.LookupDir, appSettings.AutoSaveTime.ToString(),
            appSettings.ShowStatusBar.ToString()});

        // Change the settings.
        appSettings.AspectRatio   = 1.250F;
        appSettings.LookupDir     = @"C:\Temp";
        appSettings.AutoSaveTime  = 10;
        appSettings.ShowStatusBar = true;

        // Save the new settings.
        appSettings.Close();
    }
}

// Store and retrieve application settings.
class AppSettings
{
    const string fileName = "AppSettings#@@#.dat";
    float  aspectRatio;
    string lookupDir;
    int    autoSaveTime;
    bool   showStatusBar;

    public float AspectRatio
    {
        get{ return aspectRatio; }
        set{ aspectRatio = value; }
    }

    public string LookupDir
    {
        get{ return lookupDir; }
        set{ lookupDir = value; }
    }

    public int AutoSaveTime
    {
        get{ return autoSaveTime; }
        set{ autoSaveTime = value; }
    }

    public bool ShowStatusBar
    {
        get{ return showStatusBar; }
        set{ showStatusBar = value; }
    }

    public AppSettings()
    {
        // Create default application settings.
        aspectRatio   = 1.3333F;
        lookupDir     = @"C:\AppDirectory";
        autoSaveTime  = 30;
        showStatusBar = false;

        if(File.Exists(fileName))
        {
            BinaryReader binReader =
                new BinaryReader(File.Open(fileName, FileMode.Open));
            try
            {
                // If the file is not empty,
                // read the application settings.
                // Read 4 bytes into a buffer to
                // determine if the file is empty.
                byte[] testArray = new byte[3];
                int count = binReader.Read(testArray, 0, 3);

                if (count != 0)
                {
                    aspectRatio   = binReader.ReadSingle();
                    lookupDir     = binReader.ReadString();
                    autoSaveTime  = binReader.ReadInt32();
                    showStatusBar = binReader.ReadBoolean();
                }
            }

            // If the end of the stream is reached before reading
            // the four data values, ignore the error and use the
            // default settings for the remaining values.
            catch(EndOfStreamException e)
            {
                Console.WriteLine("{0} caught and ignored. " +
                    "Using default values.", e.GetType().Name);
            }
            finally
            {
                binReader.Close();
            }
        }

    }

    // Create a file and store the application settings.
    public void Close()
    {
        using(BinaryWriter binWriter =
            new BinaryWriter(File.Open(fileName, FileMode.Create)))
        {
            binWriter.Write(aspectRatio);
            binWriter.Write(lookupDir);
            binWriter.Write(autoSaveTime);
            binWriter.Write(showStatusBar);
        }
    }
}

Visual C++
using namespace System;
using namespace System::IO;
using namespace System::Security::Permissions;

// Store and retrieve application settings.
ref class AppSettings
{
private:
   static String^ fileName =  "AppSettings#@@#.dat";
   float aspectRatio;
   String^ lookupDir;
   int autoSaveTime;
   Boolean showStatusBar;

public:

   property float AspectRatio
   {
      float get()
      {
         return aspectRatio;
      }

      void set( float value )
      {
         aspectRatio = value;
      }

   }

   property String^ LookupDir
   {
      String^ get()
      {
         return lookupDir;
      }

      void set( String^ value )
      {
         lookupDir = value;
      }

   }

   property int AutoSaveTime
   {
      int get()
      {
         return autoSaveTime;
      }

      void set( int value )
      {
         autoSaveTime = value;
      }

   }

   property Boolean ShowStatusBar
   {
      Boolean get()
      {
         return showStatusBar;
      }

      void set( Boolean value )
      {
         showStatusBar = value;
      }

   }
   AppSettings()
   {

      // Create default application settings.
      aspectRatio = 1.3333F;
      lookupDir =  "C:\\AppDirectory";
      autoSaveTime = 30;
      showStatusBar = false;
      if ( File::Exists( fileName ) )
      {

         BinaryReader^ binReader = gcnew BinaryReader( File::Open( fileName, FileMode::Open ) );
         try
         {


            // If the file is not empty,
            // read the application settings.
            // Read 4 bytes into a buffer to
            // determine if the file is empty.
            array<Byte>^testArray = gcnew array<Byte>(3);
            int count = binReader->Read(testArray, 0, 3);
            if ( count != -1 )
            {
               aspectRatio = binReader->ReadSingle();
               lookupDir = binReader->ReadString();
               autoSaveTime = binReader->ReadInt32();
               showStatusBar = binReader->ReadBoolean();
               return;
            }
         }
         // If the end of the stream is reached before reading
         // the four data values, ignore the error and use the
         // default settings for the remaining values.
         catch ( EndOfStreamException^ e )
         {
            Console::WriteLine( "{0} caught and ignored. "
            "Using default values.", e->GetType()->Name );
         }
         finally
         {
            binReader->Close();
         }


      }
   }


   // Create a file and store the application settings.
   void Close()
   {

      BinaryWriter^ binWriter = gcnew BinaryWriter( File::Open( fileName, FileMode::Create ) );
      try
      {
         binWriter->Write( aspectRatio );
         binWriter->Write( lookupDir );
         binWriter->Write( autoSaveTime );
         binWriter->Write( showStatusBar );
      }
      finally
      {
         binWriter->Close();
      }


   }

};

int main()
{

   // Load application settings.
   AppSettings^ appSettings = gcnew AppSettings;
   array<Object^>^someObject = {appSettings->AspectRatio.ToString(),appSettings->LookupDir,appSettings->AutoSaveTime.ToString(),appSettings->ShowStatusBar.ToString()};
   Console::WriteLine( "App settings.\nAspect Ratio: {0}, "
   "Lookup directory: {1},\nAuto save time: {2} minutes, "
   "Show status bar: {3}\n", someObject );

   // Change the settings.
   appSettings->AspectRatio = 1.250F;
   appSettings->LookupDir =  "C:\\Temp";
   appSettings->AutoSaveTime = 10;
   appSettings->ShowStatusBar = true;

   // Save the new settings.
   appSettings->Close();
}


J#
import System.*;
import System.IO.*;
import System.Security.Permissions.*;

class Test
{
    public static void main(String[] args)
    {
        // Load application settings.
        AppSettings appSettings = new AppSettings();
        Console.WriteLine("App settings.\nAspect Ratio: {0}, "
            + "Lookup directory: {1},\nAuto save time: {2} minutes, "
            + "Show status bar: {3}\n",
            new Object[]{System.Convert.ToString(appSettings.get_AspectRatio()),
            appSettings.get_LookupDir(),
            System.Convert.ToString(appSettings.get_AutoSaveTime()),
            System.Convert.ToString(appSettings.get_ShowStatusBar())});

        // Change the settings.
        appSettings.set_AspectRatio(1.25F);
        appSettings.set_LookupDir("C:\\Temp");
        appSettings.set_AutoSaveTime ( 10);
        appSettings.set_ShowStatusBar( true);

        // Save the new settings.
        appSettings.Close();
    } //main
} //Test

// Store and retrieve application settings.
class AppSettings
{
    private String fileName = "AppSettings#@@#.dat";
    private float aspectRatio;
    private String lookupDir;
    private int autoSaveTime;
    private boolean showStatusBar;

    /** @property
     */
    public float get_AspectRatio()
    {
        return aspectRatio ;
    }//get_AspectRatio

    /** @property
     */
    public void set_AspectRatio ( float value )
    {
        aspectRatio = value;
    }//set_AspectRatio

    /** @property
     */
    public String get_LookupDir()
    {
        return lookupDir ;
    }//get_LookupDir

    /** @property
     */
    public void set_LookupDir ( String value )
    {
        lookupDir = value;
    }//set_LookupDir

    /** @property
     */
    public int get_AutoSaveTime()
    {
        return autoSaveTime ;
    }//get_AutoSaveTime

    /** @property
     */
    public void set_AutoSaveTime ( int value )
    {
        autoSaveTime = value;
    }//set_AutoSaveTime

    /** @property
     */
    public boolean get_ShowStatusBar()
    {
        return showStatusBar ;
    }//get_ShowStatusBar

    /** @property
     */
    public void set_ShowStatusBar ( boolean value )
    {
        showStatusBar = value;
    }//set_ShowStatusBar

    public AppSettings()
    {
        // Create default application settings.
        aspectRatio = 1.3333F;
        lookupDir = "C:\\AppDirectory";
        autoSaveTime = 30;
        showStatusBar = false;

        if ( File.Exists(fileName) ) {
            BinaryReader binReader =
                new BinaryReader(File.Open(fileName, FileMode.Open));
            try {

                // If the file is not empty,
                // read the application settings.
                // Read 4 bytes into a buffer to
                // determine if the file is empty.
                ubyte[] testArray = new ubyte[3];
                int count = binReader.Read(testArray, 0, 3);
                if (count != 0)
                {
                    aspectRatio = binReader.ReadSingle();
                    lookupDir = binReader.ReadString();
                    autoSaveTime = binReader.ReadInt32();
                    showStatusBar = binReader.ReadBoolean();
                }
            }

            // If the end of the stream is reached before reading
            // the four data values, ignore the error and use the
            // default settings for the remaining values.
            catch(EndOfStreamException e) {
                Console.WriteLine("{0} caught and ignored. "
                    + "Using default values.", e.GetType().get_Name());
            }
            finally {
                binReader.Close();
            }
        }
    } //AppSettings

    // Create a file and store the application settings.
    public void Close()
    {
        BinaryWriter binWriter =
            new BinaryWriter(File.Open(fileName, FileMode.Create));
        try {
            binWriter.Write(aspectRatio);
            binWriter.Write(lookupDir);
            binWriter.Write(autoSaveTime);
            binWriter.Write(showStatusBar);
        }
        finally {
            if ( binWriter != null ) {
                binWriter= null;
            }
        }
    } //Close
} //AppSettings

System..::.Object
  System.IO..::.BinaryWriter
Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, 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

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: 2.0, 1.0
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