How do I fix compiler error cs0101?

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C#

"The namespace 'classtester' already contains a definition for 'Control'." I am getting this error message and couldn't figure out how to fix it.

{
    public class Control
    {
        private int top;
        private int left;
        public Control(int top, int left)
        {
            top = top;
            left = left;
        }
        public void DrawControl()
        {
            Console.WriteLine("Drawing Control at {0}, {1}", top, left);
        }
      }
    public class ListBox: Control
{
    private string mListBoxContents;
    public ListBox(int top, int left, string theContent): base(top,left)
{
    mListBoxContents = theContent;
}
    public new void DrawControl()
{
    base.DrawControl();
    Console.WriteLine("Writing string to the ListBox: {0}", mListBoxContents);
}
}
    public class Tester
    {
        public static void Main()
        {
            Control myControl = new Control (5,10);
            myControl.DrawControl();
            ListBox lb = new ListBox (20, 30, "Hello World");
            lb.DrawControl();
        }
    }
}