Dynamically add textbox to RadDock

Question

I'm Trying to add Text Box to the raddock dynamically.When i add the text box.The textbox appears above the dock not inside the dock.Its part of dock but.Thanks in advance

        RadDock dock = CreateRadDock();//Creating the rad
        TextBox txt = new TextBox();
        dock.Controls.Add(txt);
        RadDockZone2.Controls.Add(dock);