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BinaryWriter.Seek Method

Sets the position within the current stream.

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

public virtual long Seek(
	int offset,
	SeekOrigin origin
)

Parameters

offset
Type: System.Int32

A byte offset relative to origin.

origin
Type: System.IO.SeekOrigin

A field of SeekOrigin indicating the reference point from which the new position is to be obtained.

Return Value

Type: System.Int64
The position with the current stream.

ExceptionCondition
IOException

The file pointer was moved to an invalid location.

ArgumentException

The SeekOrigin value is invalid.

For a list of common I/O tasks, see Common I/O Tasks.

The following example writes a series of byte values to a file. The example uses Seek to move to various locations in the file, and then writes marker bytes by using the Write method.

using System;
using System.IO;
using System.Text;

public class BinReadWrite
{
    public static void Main()
    {
        string testfile = @"C:\testfile.bin";

        // create a test file using BinaryWriter
        FileStream fs = File.Create(testfile);
        UTF8Encoding utf8 = new UTF8Encoding();

        BinaryWriter bw = new BinaryWriter(fs, utf8);
        // write a series of bytes to the file, each time incrementing 
        // the value from 0 - 127 
        int pos;

        for (pos = 0; pos < 128; pos++)
        {
            bw.Write((byte)pos);
        }

        // reset the stream position for the next write pass
        bw.Seek(0, SeekOrigin.Begin);
        // write marks in file with the value of 255 going forward 
        for (pos = 0; pos < 120; pos += 8)
        {
            bw.Seek(7, SeekOrigin.Current);
            bw.Write((byte)255);
        }

        // reset the stream position for the next write pass
        bw.Seek(0, SeekOrigin.End);
        // write marks in file with the value of 254 going backward 
        for (pos = 128; pos > 6; pos -= 6)
        {
            bw.Seek(-6, SeekOrigin.Current);
            bw.Write((byte)254);
            bw.Seek(-1, SeekOrigin.Current);
        }

        // now dump the contents of the file using the original file stream
        fs.Seek(0, SeekOrigin.Begin);
        byte[] rawbytes = new byte[fs.Length];
        fs.Read(rawbytes, 0, (int)fs.Length);

        int i = 0;
        foreach (byte b in rawbytes)
        {
             switch (b)
             {
                 case 254:
                 {
                     Console.Write("-%- ");
                 }
                 break;

                 case 255:
                 {
                     Console.Write("-*- ");
                 }
                 break;

                 default:
                 {
                     Console.Write("{0:d3} ", b);
                 }
                 break;
             }
             i++;
             if (i == 16)
             {
                 Console.WriteLine();
                 i = 0;
             }
        }
        fs.Close();
    }
}

//The output from the program is this: 
// 
// 000 001 -%- 003 004 005 006 -*- -%- 009 010 011 012 013 -%- -*- 
// 016 017 018 019 -%- 021 022 -*- 024 025 -%- 027 028 029 030 -*- 
// -%- 033 034 035 036 037 -%- -*- 040 041 042 043 -%- 045 046 -*- 
// 048 049 -%- 051 052 053 054 -*- -%- 057 058 059 060 061 -%- -*- 
// 064 065 066 067 -%- 069 070 -*- 072 073 -%- 075 076 077 078 -*- 
// -%- 081 082 083 084 085 -%- -*- 088 089 090 091 -%- 093 094 -*- 
// 096 097 -%- 099 100 101 102 -*- -%- 105 106 107 108 109 -%- -*- 
// 112 113 114 115 -%- 117 118 -*- 120 121 -%- 123 124 125 126 127

.NET Framework

Supported in: 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

.NET for Windows Store apps

Supported in: Windows 8

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone Silverlight 8.1, Windows Phone Silverlight 8

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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