Multiple Controls in GridView Template Field and Perform Update

First Thank You for Reading

I have an image and a dropdownlist in a GridView Template Field.

If the user clicks the image, the dropdownlist displays

When user selects dropdownlist value the new value is updated to the database

If the user clicks the image and the dropdownlist is visible then , dropdownlist visible is set to false

I can get as far as getting the index of the image, how do I build a reference to the dropdownlist in the same row.

// start aspx page
                <asp:TemplateField ShowHeader="False">
                    <ItemTemplate>
                        <asp:ImageButton
                            ID="imgRenumber"
                            runat="server"
                            CausesValidation="false"
                            CommandName="Show"
                            ImageUrl="~/Images/EETMove.gif"
                            AlternateText="Manual Renumber"
                            CommandArgument='<%# Container.DataItemIndex %>' />
                        <asp:DropDownList ID="ddlRenumber" runat="server" AutoPostBack="True"  Visible="false">
                        </asp:DropDownList>
                       
                    </ItemTemplate>
                </asp:TemplateField>
// end aspx

//start aspx.cs
// This Part Works!
     protected void grdMasterExhibit_RowCreated(object sender, GridViewRowEventArgs e)
    {
        if (e.Row.RowType == DataControlRowType.DataRow)
        {
            ImageButton button0 = (ImageButton)e.Row.FindControl("imgRenumber");
            button0.CommandArgument = e.Row.RowIndex.ToString();
        }
    }

// This Part Blows Up

    protected void grdMasterExhibit_RowCommand(object sender, GridViewCommandEventArgs e)
    {
            int index = Convert.ToInt32(e.CommandArgument); // This is the image

            GridViewRow grid0 = (GridViewRow)e.CommandSource;
           //The Error --
           // Unable to cast object of type 'System.Web.UI.WebControls.ImageButton'
          // to type 'System.Web.UI.WebControls.GridViewRow'.

            switch (e.CommandName)
            {
                case "Show":
                    DropDownList dropDown1 = (DropDownList)e.Row.FindControl("ddlRenumber");
                   // The Row here is invalid because image is coming in not the grid view
                    dropDown1.Visible = true;
                    break;

                case "Hide":
                    DropDownList dropDown1 = (DropDownList)e.Row.FindControl("ddlRenumber");
                   // The Row here is invalid because image is coming in not the grid view
                    dropDown1.Visible = false;
                    break;

            }

    }
}

//end aspx.cs