GridView Add TextBox TemplateField Into Footer CodeBehind

Question

Suppose I have one template field

TemplateField FooterField = new TemplateField();

FooterField.ItemTemplate = //my code (basically setting it to display a button)

I then define what the FooterField should do during gridview editing mode like this:

FooterField.EditItemTemplate = //my code (entering editing mode when the button is clicked)

Now my question is: how can I insert this TemplateField into the gridview Footer?