C＃动态地将文本添加到tabcontrol

Having a slight problem on C#, still quite new to the language but hoping you can help. I have a program which dynamically creates tab forms and then I'm trying to add controls to the tabform (text boxes and labels), but no matter what I try it just doesn't seem to want to work. Here's the code I'm currently using (just to get one textbox in each form):Having a slight problem on C#, still quite new