Question

I have user control with a gridview, but for some reason I can’t use the asp controls from within the backend code.
In the other user controls I can use them normally but at this particular user control it gives me error when I am trying to use a control which is used in the gridview.
Here is the code for my gridview, please let me know if you notice something unusual:

<asp:GridView ID="gvGDG" runat="server" AutoGenerateColumns="False" 
    DataKeyNames="ID" DataSourceID="SqlDataSource1" Width="100%" CssClass="mGrid" GridLines="None" PagerStyle-CssClass="pgr" AlternatingRowStyle-CssClass="alt"
    AllowPaging="True" >
<AlternatingRowStyle CssClass="alt"></AlternatingRowStyle>
    <Columns>
        <asp:CommandField ShowDeleteButton="True" ShowEditButton="True" 
            ItemStyle-HorizontalAlign="Center" CausesValidation="False">
        </asp:CommandField>
        <asp:BoundField DataField="ID" HeaderText="ID" 
            SortExpression="ID" InsertVisible="False" ReadOnly="True" 
            ItemStyle-HorizontalAlign="Center" >
        </asp:BoundField>      
        <asp:TemplateField HeaderText="Country" SortExpression="Country">
            <ItemTemplate>
                <asp:Label ID="Label1" runat="server" Text='<%# Bind("Country") %>'></asp:Label>
            </ItemTemplate>
            <EditItemTemplate>
            <asp:UpdatePanel ID="countrypanel" runat="server">            
            <ContentTemplate>
            <asp:DropDownList ID="ddlCountry" runat="server" DataTextField="name" DataValueField="ID"  onselectedindexchanged="ddlcountry_SelectedIndexChanged" AppendDataBoundItems="true" AutoPostBack="true" />
            </ContentTemplate>
            <Triggers>
            <asp:AsyncPostBackTrigger ControlID="ddlCountry" />
            </Triggers>
            </asp:UpdatePanel>
            </EditItemTemplate>
            <ItemStyle HorizontalAlign="Center" />
        </asp:TemplateField>
        <asp:TemplateField HeaderText="State Province" SortExpression="State_Province">
            <ItemTemplate>
                <asp:Label ID="Label2" runat="server" Text='<%# Bind("State_Province") %>'></asp:Label>
            </ItemTemplate>
            <EditItemTemplate>
                             <asp:DropDownList ID="ddlState" runat="server" DataSourceID="SqlDataSource3" SelectedValue='<%# Bind("State_Province") %>'
                                 DataTextField="StateName" DataValueField="StateName">
                </asp:DropDownList>
                             <asp:SqlDataSource ID="SqlDataSource3" runat="server" 
                                 ConnectionString="<%$ ConnectionStrings:ApplicationServices %>" 
                                 SelectCommand="SELECT [StateName] FROM [States]"></asp:SqlDataSource>
            </EditItemTemplate>
            <ItemStyle HorizontalAlign="Center" />
        </asp:TemplateField>
                <asp:TemplateField HeaderText="GDG Type" SortExpression="State_Province">
            <ItemTemplate>
                <asp:Label ID="Label3" runat="server" Text='<%# Bind("GDG_Type") %>'></asp:Label>
            </ItemTemplate>
            <EditItemTemplate>
                             <asp:DropDownList ID="ddlGdg" runat="server" DataSourceID="SqlDataSource4" SelectedValue='<%# Bind("GDG_Type") %>'
                                 DataTextField="GDG" DataValueField="GDG">
                </asp:DropDownList>
                             <asp:SqlDataSource ID="SqlDataSource4" runat="server" 
                                 ConnectionString="<%$ ConnectionStrings:ApplicationServices %>" 
                                 SelectCommand="SELECT [GDG] FROM [GDG]"></asp:SqlDataSource>
            </EditItemTemplate>
            <ItemStyle HorizontalAlign="Center" />
        </asp:TemplateField>

          <asp:TemplateField HeaderText="Energy Type UOM" SortExpression="Energy_Type_UOM">
            <ItemTemplate>
                <asp:Label ID="Label4" runat="server" Text='<%# Bind("Energy_Type_UOM") %>'></asp:Label>
            </ItemTemplate>
            <EditItemTemplate>
                             <asp:DropDownList ID="ddlUomEnergy" runat="server" DataSourceID="SqlDataSource5" SelectedValue='<%# Bind("Energy_Type_UOM") %>'
                                 DataTextField="UOM" DataValueField="UOM">
                </asp:DropDownList>
                             <asp:SqlDataSource ID="SqlDataSource5" runat="server" 
                                 ConnectionString="<%$ ConnectionStrings:ApplicationServices %>" 
                                 SelectCommand="SELECT UOM FROM UOM WHERE (Type = 'E')"></asp:SqlDataSource>
            </EditItemTemplate>
            <ItemStyle HorizontalAlign="Center" />
        </asp:TemplateField>


                      <asp:TemplateField HeaderText="GDG UOM" SortExpression="GDG_UOM">
            <ItemTemplate>
                <asp:Label ID="Label5" runat="server" Text='<%# Bind("GDG_UOM") %>'></asp:Label>
            </ItemTemplate>
            <EditItemTemplate>
                             <asp:DropDownList ID="ddlUom" runat="server" DataSourceID="SqlDataSource6" SelectedValue='<%# Bind("GDG_UOM") %>'
                                 DataTextField="UOM" DataValueField="UOM">
                </asp:DropDownList>
                             <asp:SqlDataSource ID="SqlDataSource6" runat="server" 
                                 ConnectionString="<%$ ConnectionStrings:ApplicationServices %>" 
                                 SelectCommand="SELECT UOM FROM UOM WHERE (Type = 'O')"></asp:SqlDataSource>
            </EditItemTemplate>
            <ItemStyle HorizontalAlign="Center" />
        </asp:TemplateField>     
        <asp:BoundField DataField="GDG_Coeficient_Value" 
            HeaderText="GDG Coeficient Value" SortExpression="GDG Coeficient Value" 
            ItemStyle-HorizontalAlign="Center" >
<ItemStyle HorizontalAlign="Center"></ItemStyle>
        </asp:BoundField>
    </Columns>

<PagerStyle CssClass="pgr"></PagerStyle>
</asp:GridView>

Thanks in advance, Laziale

Answer 1

If I m right then. You have a User Control. Say wucMyControl.ascx, where you have a gridview control gvGDG. And u are unable to access it from wucMyControl.ascx.cs. If its the problem then use the solution below:

In your user controls designer file check the access level of the Gridview control. Might be it will get changed to private, accidently , instead of protected. If its private , make it protected or public and check whether you are able to access it now or not.

Update
FYI, you can’t access directly the child controls. For this you need to access in the controls DataBound event.

Here in your case :

protected void GridView_RowDataBound(sender, e)
{
    if(e.Row.RowType == DataControlRowtype.DataRow)
     {
          var ddl = (DropdownList)e.Row.FindControl("ddlCountry");
          // do whatever you want with ddl. Similarly you can find all html and server control inside a gridview.
     }
}

This will help you…

Adding event to gridview child controls

In your GridView1_RowDataBound method, add the handler when you create the drop down by calling ddl.SelectedIndexChanged += new EventHandler(ddl_SelectedIndexChanged);

Then, declare the void ddl_SelectedIndexChanged(object sender, EventArgs e) method to handle your logic. The sender argument will be a reference to the drop down’s that was selected. Also set AutoPostback property of the drodownlist to true.