Question

The following code outputs the result to a csv file. Lets say there are 10 values in the ‘valueDataList’ … When this is run, only one row is outputted to the file. How can I loop through the code to print the file for all values ‘at once’ in “valueDataList”.

   foreach (var value in valueDataList)

    {
        var value1 = xxxxxxx    // this value is set here based on a query.. 
        int value2 = xxxxxxxx   // this value is set here based on a query.. 

        byte[] content;

        using (var ms = new MemoryStream())  
           {
              using (var writer = new StreamWriter(ms))
                {
                  writer.WriteLine("ValueHeading1   " + " ValueHeading2");
                  writer.WriteLine(value1 + "              " + value2);                         
                }
                  content = ms.ToArray();
                  return File(content, "text/csv", "demo.csv");
           }
    }   

Basically I want to be able to append to an existing csv file on each loop iteration. How can I do this? thanks for your help.

Answer 1

Do you mean you want to write all rows from valueDataList to a csv-file?
If so;

using (var ms = new MemoryStream())  
using (var writer = new StreamWriter(ms))
{
    writer.WriteLine("ValueHeading1   " + " ValueHeading2");

    foreach (var value in valueDataList)
    {
        var value1 = xxxxxxx    // this value is set here based on a query.. 
        int value2 = xxxxxxxx   // this value is set here based on a query.. 

        writer.WriteLine(value1 + "              " + value2);                         
    }   

    byte[] content = ms.ToArray();
    return File(content, "text/csv", "demo.csv");
}