How to download a file in ASP.Net

Here is perhaps the simplest, shortest way to download a file in an ASP.Net application:

Response.ContentType = "application/pdf";

Response.AppendHeader("Content-Disposition", "attachment; filename=MyFile.pdf");

Response.TransmitFile(Server.MapPath("~/Files/MyFile.pdf"));

Response.End();

The first step is to set the content type.   In the example above, we're downloading a .pdf file.  Here are some of the most common content types:

.htm, .html     Response.ContentType = "text/HTML";

.txt    Response.ContentType = "text/plain";

.doc, .rtf, .docx    Response.ContentType = "Application/msword";

.xls, .xlsx    Response.ContentType = "Application/x-msexcel";

.jpg, .jpeg    Response.ContentType = "image/jpeg";

.gif    Response.ContentType =  "image/GIF";

.pdf    Response.ContentType = "application/pdf";

Response.TransmitFile retrieves a file and writes it to the Response.  By calling TransmitFile, you are ensuring that the Open / Save dialong will open on the browser, as opposed to simply opening the file in the browser window.

 

In some cases, we can't call TransmitFile because we can't map a path to the file.  Instead, we'll get the file as a Stream and write it to the Response object: 

Response.ContentType = "application/pdf";

Response.AppendHeader("Content-Disposition", "attachment; filename=MyFile.pdf");

// Write the file to the Response

const int bufferLength = 10000;

byte[] buffer = new Byte[bufferLength];

int length = 0;

Stream download = null;

try

{

    download = new FileStream(Server.MapPath("~/Files/Lincoln.txt"),

                                                   FileMode.Open,

                                                   FileAccess.Read);

    do

    {

        if (Response.IsClientConnected)

        {

            length = download.Read(buffer, 0, bufferLength);

            Response.OutputStream.Write(buffer, 0, length);

            buffer = new Byte[bufferLength];

        }

        else

        {

            length = -1;

        }

    }

    while (length > 0);

    Response.Flush();

    Response.End();

}

finally

{

    if (download != null)

        download.Close();

}

As before, the Open / Save dialog should open in the browser.