FileStream::WriteByte Method (Byte)


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

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

virtual void WriteByte(
	unsigned char value
) override


Type: System::Byte

A byte to write to the stream.

Exception Condition

The stream is closed.


The stream does not support writing.

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.


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.

For a list of common file and directory operations, see Common I-O Tasks.

The following code example shows how to write data to a file, byte by byte, and then verify that the data was written correctly.

using namespace System;
using namespace System::IO;
int main()
   String^ fileName =  "Test@##@.dat";

   // Create random data to write to the file.
   array<Byte>^dataArray = gcnew array<Byte>(100000);
   (gcnew Random)->NextBytes( dataArray );
   FileStream^ fileStream = gcnew 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  -1;

      Console::WriteLine( "The data was written to {0} "
      "and verified.", fileStream->Name );


Universal Windows Platform
Available since 10
.NET Framework
Available since 1.1
Available since 2.0
Windows Phone Silverlight
Available since 7.0
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