Why do I get error message ‘The control ‘_ctl1’ of type ‘TextBox’ must be inside a form label with runat=server’ while trying to place a control inside a form dynamically

You are probably adding the textbox into the Page directly instead of adding it to the Page’s form. Try doing this:

VB.NET

Me.Page.Controls(1).Controls.Add(txtboxctrl)

C#

this.Page.Controls[1].Controls.Add(txtboxctrl);