using System.IO;
            // create a writer and open the file
            TextWriter tw = new StreamWriter("test.txt");
 
            // write a line of text to the file
            tw.WriteLine("My output...");
 
            // close the stream
            tw.Close();

using System.IO;
            // create a writer and open the file
            TextWriter tw = new StreamWriter("test.csv");
 
            // write a line of text to the file
            tw.WriteLine("\"col1\",\"col2\",\"col3\"");
 
            // close the stream
            tw.Close();

using System.IO;
            // create a writer and open the file
            TextWriter tw = new StreamWriter("test.rtf");
 
            // write a line of text to the file
            tw.WriteLine("{\\rtf1{\\info{\\title some data}{\\author Ravenous Wolf}}\\par\\b Created: using c#\\b0\\tab\\par\\b\\b0\\tab\\tab\\line\\par");
 
            // close the stream
            tw.Close();
}