How to use RowCommand in Nested Child GridView in ASP.Net

Download the NorthWind Databaseand set the connecttionstring as

<connectionStrings>
    <add name="constr" connectionString="Data Source=WIN-CJ18T6BKTV2\SQL2005; Initial Catalog=Northwind; user ID=sa; password=pass@123" providerName="System.Data.SqlClient"/>
  </connectionStrings>

refer this link and download the demo and do the following changes

http://www.aspsnippets.com/Articles/Multilevel-N-Level-Nested-GridView-GridView-inside-GridView-in-ASPNet-with-Paging.aspx

1)Form Tag

HTML:

<form id="form1" runat="server">
    <asp:GridView ID="gvCustomers" runat="server" AutoGenerateColumns="false" CssClass="Grid"
        DataKeyNames="CustomerID" OnRowCommand="gvCustomers_RowCommand">
        <Columns>
            <asp:TemplateField>
                <ItemTemplate>
                    <asp:ImageButton ID="imgOrdersShow" runat="server" OnClick="Show_Hide_OrdersGrid"
                        ImageUrl="~/images/plus.png" CommandArgument="Show" />
                    <asp:Panel ID="pnlOrders" runat="server" Visible="false" Style="position: relative">
                        <asp:GridView ID="gvOrders" runat="server" AutoGenerateColumns="false" PageSize="5"
                            AllowPaging="true" OnPageIndexChanging="OnOrdersGrid_PageIndexChanging" OnRowCommand="pnlOrders_RowCommand"
                            CssClass="ChildGrid" DataKeyNames="OrderId">
                            <Columns>
                                <asp:TemplateField>
                                    <ItemTemplate>
                                        <asp:ImageButton ID="imgProductsShow" runat="server" OnClick="Show_Hide_ProductsGrid"
                                            ImageUrl="~/images/plus.png" CommandArgument="Show" />
                                        <asp:Panel ID="pnlProducts" runat="server" Visible="false" Style="position: relative">
                                            <asp:GridView ID="gvProducts" runat="server" AutoGenerateColumns="false" PageSize="2"
                                                AllowPaging="true" OnPageIndexChanging="OnProductsGrid_PageIndexChanging" OnRowCommand="gvProducts_RowCommand"
                                                CssClass="Nested_ChildGrid">
                                                <Columns>
                                                    <asp:BoundField ItemStyle-Width="150px" DataField="ProductId" HeaderText="Product Id" />
                                                    <asp:BoundField ItemStyle-Width="150px" DataField="ProductName" HeaderText="Product Name" />
                                                    <asp:ButtonField ItemStyle-Width="150px" HeaderText="RowCommand" Text="Click Me"
                                                        ButtonType="Button" CommandName="OpenPopup" />
                                                </Columns>
                                            </asp:GridView>
                                        </asp:Panel>
                                    </ItemTemplate>
                                </asp:TemplateField>
                                <asp:BoundField ItemStyle-Width="150px" DataField="OrderId" HeaderText="Order Id" />
                                <asp:BoundField ItemStyle-Width="150px" DataField="OrderDate" HeaderText="Date" />
                                <asp:ButtonField ItemStyle-Width="150px" HeaderText="RowCommand" Text="Click Me"
                                    ButtonType="Button" CommandName="OpenPopup" />
                            </Columns>
                        </asp:GridView>
                    </asp:Panel>
                </ItemTemplate>
            </asp:TemplateField>
            <asp:BoundField ItemStyle-Width="150px" DataField="ContactName" HeaderText="Contact Name" />
            <asp:BoundField ItemStyle-Width="150px" DataField="City" HeaderText="City" />
            <asp:ButtonField ItemStyle-Width="150px" HeaderText="RowCommand" Text="Click Me"
                ButtonType="Button" CommandName="OpenPopup" />
        </Columns>
    </asp:GridView>
    </form>

2) Add the following events

protected void gvCustomers_RowCommand(object sender, GridViewCommandEventArgs e)
    {
        if (e.CommandName == "OpenPopup")
        {
            string message = "Row Command Fired";
            System.Text.StringBuilder sb = new System.Text.StringBuilder();
            sb.Append("<script type = 'text/javascript'>");
            sb.Append("window.onload=function(){");
            sb.Append("alert('");
            sb.Append(message);
            sb.Append("')};");
            sb.Append("</script>");
            ClientScript.RegisterClientScriptBlock(this.GetType(), "alert", sb.ToString());
        }
    }

    protected void pnlOrders_RowCommand(object sender, GridViewCommandEventArgs e)
    {
        if (e.CommandName == "OpenPopup")
        {
            string message = "Row Command Fired in First Child GridView";
            System.Text.StringBuilder sb = new System.Text.StringBuilder();
            sb.Append("<script type = 'text/javascript'>");
            sb.Append("window.onload=function(){");
            sb.Append("alert('");
            sb.Append(message);
            sb.Append("')};");
            sb.Append("</script>");
            ClientScript.RegisterClientScriptBlock(this.GetType(), "alert", sb.ToString());
        }
    }

    protected void gvProducts_RowCommand(object sender, GridViewCommandEventArgs e)
    {
        if (e.CommandName == "OpenPopup")
        {
            string message = "Row Command Fired in Second Child GridView";
            System.Text.StringBuilder sb = new System.Text.StringBuilder();
            sb.Append("<script type = 'text/javascript'>");
            sb.Append("window.onload=function(){");
            sb.Append("alert('");
            sb.Append(message);
            sb.Append("')};");
            sb.Append("</script>");
            ClientScript.RegisterClientScriptBlock(this.GetType(), "alert", sb.ToString());
        }
    }