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FileInfo.OpenRead Method

Creates a read-only FileStream.

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

public FileStream OpenRead()

Return Value

Type: System.IO.FileStream
A new read-only FileStream object.

ExceptionCondition
UnauthorizedAccessException

path is read-only or is a directory.

DirectoryNotFoundException

The specified path is invalid, such as being on an unmapped drive.

IOException

The file is already open.

This method returns a read-only FileStream object with the FileShare mode set to Read.

The following example opens a file as read-only and reads from it.

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

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

        // Delete the file if it exists. 
        if (!fi.Exists) 
        {
            //Create the file. 
            using (FileStream fs = fi.Create()) 
            {
                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 (FileStream fs = fi.OpenRead()) 
        {
            byte[] b = new byte[1024];
            UTF8Encoding temp = new UTF8Encoding(true);

            while (fs.Read(b,0,b.Length) > 0) 
            {
                Console.WriteLine(temp.GetString(b));
            }
        }
    }
}
//This code produces output similar to the following;  
//results may vary based on the computer/file structure/etc.: 
// 
//This is some text in the file. 
// 
// 
// 
// 
// 
// 
// 
// 
// 
// 
// 
//

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

.NET for Windows Phone apps

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

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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