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.

Exception Condition

fileHandler is null.


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
Available since 1.1
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