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BinaryWriter Class

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

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

public class BinaryWriter : 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.

using System;
using System.IO;
using System.Security.Permissions;

// 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;

            BinaryReader binReader =
                new BinaryReader(File.Open(fileName, FileMode.Open));
                // If the file is not empty, 
                // read the application settings. 
                // First 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)
                    // Reset the position in the stream to zero.
                    binReader.BaseStream.Seek(0, SeekOrigin.Begin);

                    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);


    // Create a file and store the application settings. 
    public void Close()
        using(BinaryWriter binWriter =
            new BinaryWriter(File.Open(fileName, FileMode.Create)))

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(),

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

        // Save the new settings.


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 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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