[C#] Create/Open File and Clear all the text

Stream myStream;

myStream = File.Open(SetupFilePath, FileMode.OpenOrCreate); //Open or Create

myStream.Close();

myStream = File.Open(SetupFilePath, FileMode.Truncate); //Reopen and clear all the text

StreamWriter sw = new StreamWriter(myStream, System.Text.Encoding.Unicode);

sw.WriteLine("test");