CSV Download from a Web App

Question

First, Thanks for any assistance I receive.
I have a Dataset that I am using to populate a .CSV file and provide the ability for the end user to 'download' the resulting file. I am populating the dataset and populating a DataTable with it. I am then creating the Folder and File with the extension '.CSV'. I then populate the file row by row using a string. The file is in the correct location, format (.CSV) and properly populated at this point.

I then call a function that I have attempted to allow the user to download the file. I have attempted this in several different fashions using the Response object. All attempts are downloaded without the .CSV extension. I have pasted some of the code to preform this function below. I do trap an error that states "Unable to evaluate expression because the code is optimized or a native frame is on top of the call stack". I have 'Googled' this error and modified my VS Options>Debugging>Just-in-Time to all the Debug in mixed mode (Managed and Native). The error occurs when I step through the code at the Response.End
I have attempted this with the HtmlTextWriter, StringWriter, StreamWriter and StringBuilder all with the same result.

Can someone assist?


string strFileNameCSV = "C:\\ExportReports\\Export_CSV_" + ReportForm1.strUserID + ".csv";
//FileInfo fiBPM_Export = new FileInfo(strFileNameCSV);

//Clear Headers
Response.Clear();
Response.ClearHeaders();
//set the conttent type of the file to be downloaded
Response.ContentType = "text/comma-separated-values";

// initialize the http content-disposition header to indicate a file attachment with the filename
Response.AppendHeader("Content-Disposition", "Attachment; Filename=\"" + strFileNameCSV + "\"");

////// transfer the file byte-by-byte to the response object
//FileInfo fileToDownload = new FileInfo(strFileNameCSV);
//Response.Flush();
//Response.WriteFile(fileToDownload.FullName);
Response.WriteFile(strFileNameCSV);
//Response.TransmitFile(strFileNameCSV);
//Response.Redirect(strFileNameCSV);
Response.End();