Index was out of range. Must be non-negative and less than the size of the collection. Parameter name: index

protected void GridView1_RowUpdating(object sender, GridViewUpdateEventArgs e)
{
    SqlConnection cn = new SqlConnection("Data Source=ANCYCHACKO-TOSH;Initial Catalog=tallysoftware;Integrated Security=True");
    SqlCommand cmd = new SqlCommand();
    cn.Open();
    GridViewRow row = GridView1.Rows[e.RowIndex];
    DropDownList dropdownlist1 = (DropDownList)GridView1.Rows[e.RowIndex].FindControl("dropdownlist1");
    TextBox txtEcollected = (TextBox)row.FindControl("txtEcollected");
    TextBox txtEplan = (TextBox)row.FindControl("txtEplan");
    TextBox txtEacoll = (TextBox)row.FindControl("txtEacoll");
    DropDownList dropdownlist2 = (DropDownList)GridView1.Rows[e.RowIndex].FindControl("dropdownlist2");
    TextBox txtEre = (TextBox)row.FindControl("txtEre");
    TextBox txtEdescrptn = (TextBox)row.FindControl("txtEdescrptn");
    int Id = Convert.ToInt32(GridView1.DataKeys[e.RowIndex].Value.ToString());
    string se_name = dropdownlist1.SelectedItem.Text;
    string collected_date = txtEcollected.Text;
    string amount_plan = txtEplan.Text;
    string amount_collected = txtEacoll.Text;
    string status_ar = dropdownlist2.SelectedItem.Text;
    string remark = txtEre.Text;
    string description = txtEdescrptn.Text;
    cmd.CommandText = "UPDATE tbl_bill SET se_name='" + dropdownlist1.SelectedItem.Text + "' ,collected_date ='" + txtEcollected.Text + "',amount_plan ='" + txtEplan.Text + "',amount_collected ='" + txtEacoll.Text + "',status_ar ='" + dropdownlist2.SelectedItem.Text + "',remark='" + txtEre.Text + "',description='" + txtEdescrptn.Text + "' WHERE id=" + Id + "'";
    cmd.ExecuteNonQuery();

    GridView1.EditIndex = -1;

    Grid();
    cn.Close();
}