WriteFile Method (IntPtr, Int64, Int64)
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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 Sub WriteFile ( _
	fileHandle As IntPtr, _
	offset As Long, _
	size As Long _


Type: System.IntPtr
The file handle 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.


fileHandler is Nothing.


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.

Dim FileName As String
Dim MyFileStream As FileStream
Dim FileHandle As IntPtr
Dim StartPos As Long = 0
Dim FileSize As Long

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)


.NET Framework

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

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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