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File.OpenText Method

.NET Framework 4

Opens an existing UTF-8 encoded text file for reading.

Namespace:  System.IO
Assembly:  mscorlib (in mscorlib.dll)
C#
C++
F#
VB
Copy 
public static StreamReader OpenText(
	string path
)

Parameters

path
Type: System.String
The file to be opened for reading.

Return Value

Type: System.IO.StreamReader
A StreamReader on the specified path.
Exception Condition
UnauthorizedAccessException

The caller does not have the required permission.

ArgumentException

path is a zero-length string, contains only white space, or contains one or more invalid characters as defined by InvalidPathChars.

ArgumentNullException

path is null.

PathTooLongException

The specified path, file name, or both exceed the system-defined maximum length. For example, on Windows-based platforms, paths must be less than 248 characters, and file names must be less than 260 characters.

DirectoryNotFoundException

The specified path is invalid, (for example, it is on an unmapped drive).

FileNotFoundException

The file specified in path was not found.

NotSupportedException

path is in an invalid format.

This method is equivalent to the StreamReader(String) constructor overload.

The path parameter is permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. To obtain the current working directory, see GetCurrentDirectory.

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

The following example opens a text file for reading.

C#
C++
VB
Copy 

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

class Test 
{
    public static void Main() 
    {
        string path = @"c:\temp\MyTest.txt";

        // Delete the file if it exists.
        if (!File.Exists(path)) 
        {
            // Create the file.
            using (FileStream fs = File.Create(path)) 
            {
                Byte[] info = 
                    new UTF8Encoding(true).GetBytes("This is some text in the file.");

                // Add some information to the file.
                fs.Write(info, 0, info.Length);
            }
        }

        // Open the stream and read it back.
        using (StreamReader sr = File.OpenText(path)) 
        {
            string s = "";
            while ((s = sr.ReadLine()) != null) 
            {
                Console.WriteLine(s);
            }
        }
    }
}

.NET Framework

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

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

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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Sample Using PowerShell 
<#
.SYNOPSIS
    This script creates a file, then reads it and displays the output.
.DESCRIPTION
    This script reimplements the MSDN sample for this page. It first creates a file (assuming the file
    does not already exist) and writes three lines to it. The script then opens the file, reads each
    line and displays it.

.NOTES
    File Name  : Copy-File2.ps1
    Author     : Thomas Lee - tfl@psp.co.uk
    Requires   : PowerShell Version 2.0
.LINK
    This script posted to:
       http://pshscripts.blogspot.com/2010/07/copy-file2ps1.html 
    MSDN Sample posted at:
        http://msdn.microsoft.com/en-us/library/system.io.file.aspx 
.EXAMPLE
    PSH [C:\foo]: . 'E:\PowerShellScriptLib\System.Io.File\Copy-File2.PS1'
    Hello
    And
    Welcome 
#>

# Set name of file to use for this script
$path = "c:\foo\MyTest.txt"

# Create the file if it does not already exist
if (![System.IO.File]::Exists($path))  {
  $sw = [System.Io.File]::CreateText($path)
  $sw.WriteLine("Hello")
  $sw.WriteLine("And")
  $sw.WriteLine("Welcome")
}

# Open the file to read from and set $s to an empty string
$sr = [System.Io.File]::OpenText($path)
$s = "";

# Loop through the file, line at a time and display the output
while (($s = $sr.ReadLine()) -ne $null)  {
  $s
}

# And close the reader/writer
$sw.Close()
$sr.Close()
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