FileStream.ReadByte Method

Definition

Namespace:

System.IO

Assembly:

System.Runtime.dll

Source:

FileStream.cs

Reads a byte from the file and advances the read position one byte.

public:
 override int ReadByte();

public override int ReadByte ();

override this.ReadByte : unit -> int

Public Overrides Function ReadByte () As Integer

Returns

Int32

The byte, cast to an Int32, or -1 if the end of the stream has been reached.

Exceptions

NotSupportedException

The current stream does not support reading.

ObjectDisposedException

The current stream is closed.

Examples

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 );
   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( "Error writing data." );
            return  -1;
         }

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

}

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);
        }
    }
}

open System
open System.IO


let fileName = "Test#@@#.dat"

// Create random data to write to the file.
let dataArray = Array.zeroCreate 100000
Random.Shared.NextBytes dataArray

do
    use fileStream = new FileStream(fileName, FileMode.Create)
    // Write the data to the file, byte by byte.
    for i = 0 to dataArray.Length - 1 do
        fileStream.WriteByte dataArray[i]

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

    // Read and verify the data.
    for i in 0L .. fileStream.Length - 1L do
        if dataArray[int i] <> (fileStream.ReadByte() |> byte) then
            printfn "Error writing data."
            exit 1

    printfn $"The data was written to {fileStream.Name} and verified."

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

Remarks

This method overrides ReadByte.

Note

Use the CanRead property to determine whether the current instance supports reading. For additional information, see CanRead.

Notes to Inheritors

The default implementation on Stream creates a new single-byte array and then calls Read(Byte[], Int32, Int32). 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.

See also

• File and Stream I/O
• How to: Read Text from a File
• How to: Write Text to a File