Right Click on GridView select Edit Column.
U will find "Template" , Add Template Field.
In template Field U can Drag Textbox,Button, RadioButton,CheckBox.
For Adding some value/row to Grid, just insert a data into database and rebind the Grid. Below is the code for binding the grid ;) .
public void LoadGrid()
{
DataTable dt = new DataTable();
sqlcon = new SqlConnection(con );
sqlcon.Open();
SqlDataAdapter sda = new SqlDataAdapter();
string strQuery = "select * from employee ";
SqlCommand cmd = new SqlCommand(strQuery);
cmd.CommandType = CommandType.Text;
cmd.Connection = sqlcon;
sda.SelectCommand = cmd;
sda.Fill(dt);
GridView1.DataSource = dt;
GridView1.DataBind();
}
Hope this is enough to solve ur problem