Yes. It's UTF8 encoding, I beleive.  Here is my code:

class Class1
{
    public static void Main(string[] args)
    {
        string degree = ("°");
        string sFile = "testingAscii.csv";
        System.IO.StreamWriter writer =
            System.IO.File.CreateText(sFile);
       
        try
        {
            writer.Write(degree);
        }
        finally
        {
            writer.Close();
        }
        System.Diagnostics.Process.Start(sFile);
    }
}

Thanks for any advice.