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FileStream.WriteByte Method

Writes a byte to the current position in the file stream.

[Visual Basic]
Overrides Public Sub WriteByte( _
   ByVal value As Byte _
)
[C#]
public override void WriteByte(
 byte value
);
[C++]
public: void WriteByte(
 unsigned char value
);
[JScript]
public override function WriteByte(
   value : Byte
);

Parameters

value
A byte to write to the stream.

Exceptions

Exception Type Condition
ObjectDisposedException The stream is closed.
NotSupportedException The stream does not support writing.

Remarks

This method overrides WriteByte.

Use WriteByte to write a byte to a FileStream efficiently. If the stream is closed or not writable, an exception will be thrown.

Note   Use the CanWrite property to determine whether the current instance supports writing. For additional information, see CanWrite.

Notes to Implementers:  The default implementation on Stream creates a new single-byte array and then calls Write. While this is formally correct, it is inefficient. Any stream with an internal buffer should override this method and provide a much more efficient version that reads the buffer directly, avoiding the extra array allocation on every call.

The following table lists examples of other typical or related I/O tasks.

To do this... See the example in this topic...
Create a text file. Writing Text to a File
Write to a text file. Writing Text to a File
Read from a text file. Reading Text from a File
Append text to a file. Opening and Appending to a Log File

File.AppendText

FileInfo.AppendText

Rename or move a file. File.Move

FileInfo.MoveTo

Copy a file. File.Copy

FileInfo.CopyTo

Get the size of a file. FileInfo.Length
Get the attributes of a file. File.GetAttributes
Set the attributes of a file. File.SetAttributes
Determine if a file exists. File.Exists
Read from a binary file. Reading and Writing to a Newly Created Data File
Write to a binary file. Reading and Writing to a Newly Created Data File
Create a directory. Directory.CreateDirectory

Directory.CreateDirectory

Example

[Visual Basic, C#, C++] The following code example shows how to write data to a file, byte by byte, and then verify that the data was written correctly.

[Visual Basic] 
Imports Microsoft.VisualBasic
Imports System
Imports System.IO
Imports System.Text

Class FStream

    Shared Sub Main()

        Const fileName As String = "Test#@@#.dat"

        ' Create random data to write to the file.
        Dim dataArray(100000) As Byte
        Dim randomGenerator As New Random()
        randomGenerator.NextBytes(dataArray)

        Dim fileStream As FileStream = _
            new FileStream(fileName, FileMode.Create)
        Try

            ' Write the data to the file, byte by byte.
            For i As Integer = 0 To dataArray.Length - 1
                fileStream.WriteByte(dataArray(i))
            Next i

            ' Set the stream position to the beginning of the stream.
            fileStream.Seek(0, SeekOrigin.Begin)

            ' Read and verify the data.
            For i As Integer = 0 To _
                CType(fileStream.Length, Integer) - 1

                If dataArray(i) <> fileStream.ReadByte() Then
                    Console.WriteLine("Error writing data.")
                    Return
                End If
            Next i
            Console.WriteLine("The data was written to {0} " & _
                "and verified.", fileStream.Name)
        Finally
            fileStream.Close()
        End Try
    
    End Sub
End Class

[C#] 
using System;
using System.IO;

class FStream
{
    static void Main()
    {
        const string fileName = "Test#@@#.dat";

        // Create random data to write to the file.
        byte[] dataArray = new byte[100000];
        new Random().NextBytes(dataArray);

        using(FileStream  
            fileStream = new FileStream(fileName, FileMode.Create))
        {
            // Write the data to the file, byte by byte.
            for(int i = 0; i < dataArray.Length; i++)
            {
                fileStream.WriteByte(dataArray[i]);
            }

            // Set the stream position to the beginning of the file.
            fileStream.Seek(0, SeekOrigin.Begin);

            // Read and verify the data.
            for(int i = 0; i < fileStream.Length; i++)
            {
                if(dataArray[i] != fileStream.ReadByte())
                {
                    Console.WriteLine("Error writing data.");
                    return;
                }
            }
            Console.WriteLine("The data was written to {0} " +
                "and verified.", fileStream.Name);
        }
    }
}

[C++] 
#using <mscorlib.dll>
using namespace System;
using namespace System::IO;

void main()
{
    String* fileName = "Test@##@.dat";

    // Create random data to write to the file.
    Byte dataArray __gc[]  = new Byte __gc[100000];
    (new Random())->NextBytes(dataArray);

    FileStream* fileStream = 
        new FileStream(fileName, FileMode::Create);
    try
    {
        // Write the data to the file, byte by byte.
        for(int i = 0; i < dataArray->Length; i++)
        {
            fileStream->WriteByte(dataArray[i]);
        }

        // Set the stream position to the beginning of the file.
        fileStream->Seek(0, SeekOrigin::Begin);

        // Read and verify the data.
        for(int i = 0; i < fileStream->Length; i++)
        {
            if(dataArray[i] != fileStream->ReadByte())
            {
                Console::WriteLine(S"Error writing data.");
                return;
            }
        }
        Console::WriteLine(S"The data was written to {0} " 
            S"and verified.", fileStream->Name);
    }
    __finally
    {
        fileStream->Close();
    }
}

[JScript] No example is available for JScript. To view a Visual Basic, C#, or C++ example, click the Language Filter button Language Filter in the upper-left corner of the page.

Requirements

Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family, .NET Compact Framework, Common Language Infrastructure (CLI) Standard

See Also

FileStream Class | FileStream Members | System.IO Namespace | Working with I/O | Reading Text from a File | Writing Text to a File

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