using C# How to Import Data from a asp.net GridView to a CSV File

Can you import data from a CSV file and insert it into a ASP.NET GridView?  If so, can you provide a code example.

My code that I have so far: (which does not work):

 //CSV file input
        if (radDataInputFormat.SelectedValue == "3") -- I am allowing the user to select which data format that they want to use to insert/import data into the grid - this is for CSV
        {
            if (System.IO.File.Exists(fileUploadSI.FileName.ToString()))
            {
                System.IO.StreamReader fileReader = new StreamReader(fileUploadSI.FileName);

                //Check the end of file's content
                if (fileReader.Peek() != -1)
                {
                    string fileRow = fileReader.ReadLine();
                    string[] fileDateField = fileRow.Split(',');
                }
                //Close the StreamReader
                fileReader.Close();
            }
        }

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