ReadByte Method

FileStream.ReadByte Method ()


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

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

public override int ReadByte()

Return Value

Type: System.Int32

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

Exception Condition

The current stream does not support reading.


The current stream is closed.

This method overrides ReadByte.


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

Notes to Implementers:

The default implementation on Stream creates a new single-byte array and then calls Read. 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 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);

            fileStream = new FileStream(fileName, FileMode.Create))
            // Write the data to the file, byte by byte.
            for(int i = 0; i < dataArray.Length; 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.");
            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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