C# Writing debug output to .txt file

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C#

I'm running code and I want my debug output to write to a text file. how does this work?
I tried to write :

TextWriterTraceListener[] listeners = new TextWriterTraceListener[] {
                new TextWriterTraceListener("W:\\C.txt"),
              new TextWriterTraceListener(Console.Out)

Debug.Listeners.AddRange(listeners);
Debug.WriteLine("Some Value", "Some Category");

but it still write to the output window...
What should I do?
thanks.