Dynamic create controls problem

I wanted dynamic create some html and asp.net controls from code behind. When i click button (asp.net controls), it will run code below.
If Session("tbox") Is Nothing Then Session("tbox") = 1 Else Session("tbox") += 1 End If Dim newcontrol As New HtmlGenericControl("div") newcontrol.ID = "div" & Session("tbox") newcontrol.Style.Add("background-color", "Green") newcontrol.Style.Add("width", "150px") newcontrol.Style.Add("height", "200px") newcontrol.Style.Add("margin-left", "10px") newcontrol.InnerHtml = "This is a dynamically created HTML server control. " & Session("tbox") Mydiv.Controls.Add(newcontrol) Dim newcontrol1 As New TextBox n ...