在网格视图中获取选定的索引和下拉菜单行

Question

I have a gridview in which a cell is populated with a drop down list if certain conditions are met:

protected void viewThemeTypeAssociationsGridView_OnRowDataBound(Object sender, GridViewRowEventArgs e)
{
    if (e.Row.Cells[1].Text == " ")
    {
        if (e.Row.RowType == DataControlRowType.DataRow)
        {
            e.Row.Cells[1].Text = "Not Assigned";
            DropDownList chooseThemeTypeDropDown = (DropDownList)e.Row.FindControl("chooseThemeTypeDropDown");
            chooseThemeTypeDropDown.Visible = true;
        }
    }
}

Here is a picture:

This is many copies of a drop down list what is made visible in certain rows. How do get access to the selected index for the changed dropdown list and which row it is on?

I was thinking something like this but it doesn't work:

protected void chooseThemeTypeDropDown_OnSelectedIndexChanged(object sender, EventArgs e)
{
    DropDownList chooseThemeTypeDropDown = (DropDownList)e.Row.FindControl("chooseThemeTypeDropDown");
}

EDIT: If it helps here is the gridview:

                        <asp:GridView ID="viewThemeTypeAssociationsGridView" runat="server" AutoGenerateColumns="False"
                            BackColor="#DEBA84" BorderColor="#DEBA84" BorderStyle="None" BorderWidth="1px"
                            CellPadding="3" CellSpacing="2" DataSourceID="SqlDataSource6" OnRowDataBound="viewThemeTypeAssociationsGridView_OnRowDataBound">
                            <Columns>
                                <asp:BoundField DataField="Name" HeaderText="Name" SortExpression="Name" />
                                <asp:BoundField DataField="Type" HeaderText="Type" SortExpression="Type" />
                                <asp:TemplateField HeaderText="Choose Theme Type">
                                    <ItemTemplate>
                                        <asp:DropDownList ID="chooseThemeTypeDropDown" runat="server" DataTextField="Type" DataValueField="PK_ThemeType" AutoPostBack="true" DataSourceID="SqlDataSource9" CssClass="dropDownList" OnDataBound="chooseThemeTypeDropDown_OnDataBound" Visible="false" OnSelectedIndexChanged="viewProductAssociationsDropDown_OnSelectedIndexChanged">
                                        </asp:DropDownList>
                                        <asp:SqlDataSource ID="SqlDataSource9" runat="server" ConnectionString="<%$ ConnectionStrings:ApplicationServices %>"
                                            SelectCommand="SELECT [Type], [PK_ThemeType] FROM [ThemeType] WHERE [Deleted] = 0 ORDER BY [Type] ASC">
                                        </asp:SqlDataSource>
                                    </ItemTemplate>
                                </asp:TemplateField>
                            </Columns>
                            <FooterStyle BackColor="#F7DFB5" ForeColor="#8C4510" />
                            <HeaderStyle BackColor="#A55129" Font-Bold="True" ForeColor="White" />
                            <PagerStyle ForeColor="#8C4510" HorizontalAlign="Center" />
                            <RowStyle BackColor="#FFF7E7" ForeColor="#8C4510" />
                            <SelectedRowStyle BackColor="#738A9C" Font-Bold="True" ForeColor="White" />
                            <SortedAscendingCellStyle BackColor="#FFF1D4" />
                            <SortedAscendingHeaderStyle BackColor="#B95C30" />
                            <SortedDescendingCellStyle BackColor="#F1E5CE" />
                            <SortedDescendingHeaderStyle BackColor="#93451F" />
                        </asp:GridView>
                        <asp:SqlDataSource ID="SqlDataSource6" runat="server" ConnectionString="<%$ ConnectionStrings:ApplicationServices %>"
                            SelectCommand="SELECT [Theme].[Name], [ThemeType].[Type] FROM [Theme] LEFT OUTER JOIN [ThemeType] ON [Theme].[ThemeTypeId] = [ThemeType].[PK_ThemeType] JOIN [ProductTheme] ON [ProductTheme].[ThemeId]=[Theme].[PK_Theme] WHERE ProductTheme.ProductID LIKE @productParam AND ProductTheme.ThemeId = Theme.PK_Theme AND COALESCE([THEME].[THEMETYPEID], 'null') LIKE @assignedParam GROUP BY [Theme].[Name], [ThemeType].[Type] ORDER BY CASE WHEN [ThemeType].[Type] IS NULL THEN 0 ELSE 1 END, [Theme].[Name]">
                            <SelectParameters>
                                <asp:QueryStringParameter Name="productParam" Type="String" />
                                <asp:QueryStringParameter Name="assignedParam" Type="String" />
                            </SelectParameters>
                        </asp:SqlDataSource>

EDIT 2: Current code

protected void chooseThemeTypeDropDown_OnSelectedIndexChanged(object sender, EventArgs e)
{
    DropDownList chooseThemeTypeDropDown = sender as DropDownList;
    if (chooseThemeTypeDropDown != null)
    {
        System.Diagnostics.Debug.WriteLine(chooseThemeTypeDropDown.SelectedItem.Value.ToString());
    }
}

Answer 1

The sender will give you the control that initiated the event, like this:

protected void chooseThemeTypeDropDown_OnSelectedIndexChanged(object sender, EventArgs e)
{
    DropDownList chooseThemeTypeDropDown = sender as DropDownList;

    // Check to make sure the drop down exists before we try to work with it
    if(chooseThemeTypeDropDown != null)
    {
        // Put logic here to work with drop down list
    }
}

Answer 2

You really need to move the if (e.Row.RowType == DataControlRowType.DataRow) to the outside of your conditional in OnRowDataBound .

Now, if you set chooseThemeTypeDropDown.AutoPostBack to true, and set it to handle the OnSelectedIndexChanged event, you'll be able to find the correct instance of chooseThemeTypeDropDown by casting object sender as a DropDownList .

To get the row index, that is more difficult. The quickest, but kinda hacky way, is to append the rowindex to each chooseThemeTypeDropDown ID on the GridView's RowDataBound event.

chooseThemeTypeDropDown.ID = chooseThemeTypeDropDown.ID + e.Row.RowIndex;