deleting text only after comment(--)

My project is currently spposd to delete all thetext after the -- signs, as it represents a comment.
my code now is deleting all the text in the text in the text file, een before the comment.

here is my code so far:

static void Main( string[] args )
     {
         string line = null;
         string line_to_delete = "--";
         string desktopLocation = Environment.GetFolderPath( Environment.SpecialFolder.Desktop );
         string text = Path.Combine( desktopLocation, "tim3.txt" );
         string file = Path.Combine( desktopLocation, "tim4.txt" );
 
         using (StreamReader reader = new StreamReader( text ))
         {
             using (StreamWriter writer = new StreamWriter( file ))
             {
                 while (( line = reader.ReadLine() ) != null)
                 {
                     if (string.Compare( line, line_to_delete ) == 0)
                         File.WriteAllText( file, File.ReadAllText( text ).Replace( line_to_delete, "" ) );
                     continue;
                 }
             }
 

how can i specify that it must only delete the te
Thanks

---