See this

If you want to assign text box's value to gridview then just try it like;

int RowNo=0;

int ColNo=0;

GridView1[RowNo, ColNo].Value = Tebox1.Text;

It will add text box value into grid view's 1st row 1st col.

For label just try this one;

GridView1[RowNo, ColNo].Value = Label1.Text;

Best Luck!!!!!!!!!!!!!!
Sujit.