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HttpResponse.WriteFile Method (IntPtr, Int64, Int64)

Writes the specified file directly to an HTTP response output stream.

Namespace:  System.Web
Assembly:  System.Web (in System.Web.dll)
[SecurityPermissionAttribute(SecurityAction.Demand, UnmanagedCode = true)]
public void WriteFile(
	IntPtr fileHandle,
	long offset,
	long size
)

Parameters

fileHandle
Type: System.IntPtr

The file handle of the file to write to the HTTP output stream.

offset
Type: System.Int64

The byte position in the file where writing will start.

size
Type: System.Int64

The number of bytes to write to the output stream.

ExceptionCondition
ArgumentNullException

fileHandler is null.

HttpException

offset is less than 0.

- or -

size is greater than the file size minus offset.

When this method is used with large files, calling the method might throw an exception. The size of the file that can be used with this method depends on the hardware configuration of the Web server. For more information, see article 812406, "PRB: Response.WriteFile Cannot Download a Large File" on the Microsoft Knowledge Base Web site.

The following example writes all the contents of a text file named Login.txt (which might contain literal HTML text and input controls) directly to the output stream.

String FileName;
 FileStream MyFileStream;
 IntPtr FileHandle;
 long StartPos = 0, FileSize;

 FileName = "c:\\temp\\Login.txt";

 MyFileStream = new FileStream(FileName, FileMode.Open);
 FileHandle = MyFileStream.Handle;
 FileSize = MyFileStream.Length;

 Response.Write("<b>Login: </b>");
 Response.Write("<input type=text id=user /> ");
 Response.Write("<input type=submit value=Submit /><br><br>");

 Response.WriteFile(FileHandle, StartPos, FileSize);

 MyFileStream.Close();
    

.NET Framework

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

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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