Lets your gridview id is gv_form, your textbox id is textbox1 and your radiobutton id is rdb1 then use the following code to get the values of column name "Column1"
for (int i = 0; i <= gv_form.Rows[i].Count - 1; i++)
{
GridViewRow row = gv_form.Rows[i];
RadioButton rdb = (RadioButton)row.FindControl("rdb1");
if (rdb.Checked == true)
{
textbox1.text = row[i]["Column1"].ToString();
}
}
Thanks & Regards,
BlueSathish