For Windows Forms you can control cursor position (and selection) with txtbox.SelectionStart and txtbox.SelectionLength properties. If you want to set caret to end try this:
You can set the caret position using TextBox.CaretIndex. If the only thing you need is to set the cursor at the end, you can simply pass the string's length, eg:
txtBox.CaretIndex=txtBox.Text.Length;
You need to set the caret index at the length, not length-1, because this would put the caret before the last character.