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)

public void WriteFile (
	IntPtr fileHandle,
	long offset,
	long size
public void WriteFile (
	IntPtr fileHandle, 
	long offset, 
	long size
public function WriteFile (
	fileHandle : IntPtr, 
	offset : long, 
	size : long
Not applicable.



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


The byte position in the file where writing will start.


The number of bytes to write to the output stream.

Exception typeCondition


fileHandler is a null reference (Nothing in Visual Basic).


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 result in 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" in the Microsoft Knowledge Base.

The following example writes the entire 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);

String fileName;
FileStream myFileStream;
IntPtr fileHandle;
long startPos = 0;
long fileSize;

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

myFileStream = new FileStream(fileName, FileMode.Open);
fileHandle = myFileStream.get_Handle();
fileSize = myFileStream.get_Length();

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

get_Response().WriteFile(fileHandle, startPos, fileSize);


Windows 98, Windows Server 2000 SP4, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

Community Additions