How to download file with asp.net on buttton's onClick event?

Question

I have a String variable (in C#) that contain the full path of PDF file on my server (like that \"~/doc/help.pdf\").

I want that in click on button, this file will down

Answer 1

I would suggest the following to be placed into your button click event code.

This will provide the user with a popup to download the file. I've tested it thoroughly and use it in production code.

void btnDownloadFile_Click(object sender, EventArgs e)
{    
    string strLocalFilePath = "~/doc/help.pdf";
    string fileName = "help.pdf";

    Response.Clear();

    Stream iStream = null;

    const int bufferSize = 64 * 1024;

    byte[] buffer = new Byte[bufferSize];

    int length;

    long dataToRead;

    try
    {
        iStream = new FileStream(strLocalFilePath, FileMode.Open, FileAccess.Read, FileShare.Read);
        dataToRead = iStream.Length;
        Response.ContentType = "application/octet-stream";
        Response.AddHeader("Content-Disposition", "attachment; filename=" + fileName);

        while (dataToRead > 0)
        {
            if (Response.IsClientConnected)
            {
                length = iStream.Read(buffer, 0, bufferSize);
                Response.OutputStream.Write(buffer, 0, length);
                Response.Flush();
                buffer = new byte[bufferSize];
                dataToRead = dataToRead - length;
            }
            else
            {
                //prevent infinate loop on disconnect
                dataToRead = -1;
            }
        }
    }
    catch (Exception ex)
    {
        //Your exception handling here
    }
    finally
    {
        if (iStream != null)
        {
            iStream.Close();
        }
        Response.Close();
    }
}