HttpResponse.WriteFile Method (String, 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(
	string filename,
	long offset,
	long size


Type: System.String

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

Type: System.Int64

The byte position in the file where writing will start.

Type: System.Int64

The number of bytes to write to the output stream.


offset is less than 0.

- or -

size is greater than the file size minus offset.


The filename parameter is null.

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 text and HTML input controls) directly to the output stream.

String FileName;
 FileInfo MyFileInfo;
 long StartPos = 0, FileSize;

 FileName = "c:\\temp\\login.txt";
 MyFileInfo = new FileInfo(FileName);
 FileSize = MyFileInfo.Length;

 Response.Write("Please Login: <br>");
 Response.WriteFile(FileName, StartPos, FileSize);

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1
Was this page helpful?
(1500 characters remaining)
Thank you for your feedback
© 2015 Microsoft