How to stop an Excel process that I started from a C# .Net application?

I'm running Excel from a C# .Net application and having trouble getting the process to shut down. How can I get the Excel process to shut down correctly from my C# program?

Try this:

foreach (System.Diagnostics.Process process in System.Diagnostics.Process.GetProcessesByName("EXCEL"))
        {
            if (process.MainModule.ModuleName.ToUpper().Equals("EXCEL.EXE"))
            {
                process.Kill();
                break;
            }
        }