单击按钮后如何在数据库中保存下拉菜单项模板的选定值？

请找到图片。这是我的整个代码，我想在保存按钮单击时保存每一行。我能够从单元格0和单元格1获取值，但无法从单元格2获取值，在该单元格中我已下拉列表中的选定值。我正在获取默认值“忽略”而不是选定项。那么如何获得下拉列表的选定值？

<div>
    <asp:GridView ID="GridView2" runat="server" AutoGenerateColumns = "False" 
           OnRowDataBound = "OnRowDataBound" Width="544px">
    <Columns>
        <asp:BoundField DataField="Id" HeaderText="Id" />
        <asp:BoundField HeaderText="Name" DataField="Name" />       
        <asp:TemplateField HeaderText = "Mapping" >
        <ItemTemplate>
            <asp:DropDownList ID="DropDownList1" runat="server" style="font-size: medium; font-family: Cambria" Width="300px">
            </asp:DropDownList>
        </ItemTemplate>
    </asp:TemplateField>
    </Columns>
    </asp:GridView>
    <br />
    <asp:Button ID="Button2" runat="server" Text="Save" 
           style="font-size: medium; font-family: Cambria" BorderStyle="Groove" 
           height="32px"  Width="116px" onclick="Save_Click" />
    </div>





 private void BindGrid()
{
    DataTable dt = new DataTable();
    connection();
    cmd = new SqlCommand("Select top 0 * from  F3_BC_Product_Mapping_Data", con);
    con.Open();
    adapter = new SqlDataAdapter(cmd);
    ds = new DataSet();        
    adapter.Fill(ds, "mytable");
    int j = 1;
    dt.Columns.AddRange(new DataColumn[2] { new DataColumn("Id", typeof(int)), new DataColumn("Name", typeof(string)) });
    foreach (DataColumn column in ds.Tables[0].Columns)
    {
        dt.Rows.Add(j,column.ColumnName);
        j++;
    } 
    GridView2.DataSource = dt;
    GridView2.DataBind();
    con.Close();

}

  protected void OnRowDataBound(object sender, GridViewRowEventArgs e)
{
    if (e.Row.RowType == DataControlRowType.DataRow)
    {
        DropDownList ddlMap = (e.Row.FindControl("DropDownList1") as DropDownList);
        DataTable dt = new DataTable();
        dt = (DataTable)Session["data"];
        for (int i = 0; i < dt.Columns.Count; i++)
        {
            ddlMap.Items.Add(dt.Columns[i].Caption.ToString());
        }
        ddlMap.Items.Insert(0, new ListItem("Ignore"));
    }
}

 protected void Save_Click(object sender, EventArgs e)
{
    foreach (GridViewRow gr in GridView2.Rows)
    {

        string cell_1_Value = GridView2.Rows[gr.RowIndex].Cells[0].Text;
        string cell_2_Value = GridView2.Rows[gr.RowIndex].Cells[1].Text;
        string cell_3_Value = ((DropDownList)gr.FindControl("DropDownList1")).SelectedItem.Value;
    }
}