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POError Populating Dropdownlist in Gridview Footer Template in ASP.NET
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  1. POError Populating Dropdownlist in Gridview Footer Template in ASP.NET
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    copied!<p>I want to implement a cascading dropdownlist in a gridview footer template. My code is given below. I am getting an error message "<strong>Object reference not set to an instance of an object.</strong>"</p> <p>My ASPX Page</p> <pre><code> &lt;asp:GridView ID="GridView1" runat="server" Width="950px" AutoGenerateColumns="false" Font-Names="Segoe UI Symbol" Font-Size="11pt" AlternatingRowStyle-BackColor="White" HeaderStyle-BackColor="#3AC0F2" HeaderStyle-ForeColor="White" AllowPaging="true" ShowFooter="true" RowStyle-BackColor="#A1DCF2" OnRowEditing="GridView1_RowEditing" DataKeyNames="ServiceID" OnRowCancelingEdit="GridView1_RowCancelingEdit" OnRowCreated ="GridView1_RowCreated" PageSize="20" CellPadding="4"&gt; &lt;Columns&gt; &lt;%--ServiceID--%&gt; &lt;asp:TemplateField ItemStyle-Width="100px" HeaderText="ServiceID"&gt; &lt;ItemTemplate&gt; &lt;asp:Label ID="lblServiceID" runat="server" Text='&lt;%# Eval("ServiceId")%&gt;'&gt;&lt;/asp:Label&gt; &lt;/ItemTemplate&gt; &lt;/asp:TemplateField&gt; &lt;%--Grand Parent Service --%&gt; &lt;asp:TemplateField ItemStyle-Width="100px" HeaderText="Grand Parent"&gt; &lt;ItemTemplate&gt; &lt;asp:Label ID="lblGrandParentService" runat="server" Text='&lt;%# Eval("GrandService")%&gt;'&gt;&lt;/asp:Label&gt; &lt;/ItemTemplate&gt; &lt;EditItemTemplate&gt; &lt;asp:DropDownList ID="ddlGrandParentService" AutoPostBack="true" runat="server" Width="150" onselectedindexchanged="ddlGrandParentService_SelectedIndexChanged"&gt; &lt;/asp:DropDownList&gt; &lt;/EditItemTemplate&gt; &lt;FooterTemplate&gt; &lt;asp:DropDownList ID="ddlGrandParentService" AutoPostBack="true" runat="server" Width="150" onselectedindexchanged="ddlGrandParentService_SelectedIndexChanged"&gt; &lt;/asp:DropDownList&gt; &lt;/FooterTemplate&gt; &lt;/asp:TemplateField&gt; &lt;%-- Parent Service --%&gt; &lt;asp:TemplateField ItemStyle-Width="100px" HeaderText="Parent Service"&gt; &lt;ItemTemplate&gt; &lt;asp:Label ID="lblParentService" runat="server" Text='&lt;%# Eval("ParentServiceName")%&gt;'&gt;&lt;/asp:Label&gt; &lt;/ItemTemplate&gt; &lt;EditItemTemplate&gt; &lt;asp:DropDownList ID="ddlParentService" runat="server" Width="150" &gt; &lt;/asp:DropDownList&gt; &lt;/EditItemTemplate&gt; &lt;FooterTemplate&gt; &lt;asp:DropDownList ID="ddlParentService" runat="server" Width="150"&gt; &lt;/asp:DropDownList&gt; &lt;/FooterTemplate&gt; &lt;/asp:TemplateField&gt; &lt;/Columns&gt; &lt;/asp:GridView&gt; protected void ddlGrandParentService_SelectedIndexChanged(object sender, EventArgs e) { DropDownList ddlGrandParent = (DropDownList)sender; GridViewRow row = (GridViewRow)ddlGrandParent.NamingContainer; if (row != null) { if ((row.RowState &amp; DataControlRowState.Edit) &gt; 0) { DropDownList ddlParent = (DropDownList)row.FindControl("ddlParentService"); ddlParent.DataSource = GetParentServiceByGrandParent(Convert.ToInt32(ddlGrandParent.SelectedValue)); ddlParent.DataValueField = "ParentServiceID"; ddlParent.DataTextField = "ParentServiceName"; ddlParent.DataBind(); } } } public void GridView1_RowCreated(Object sender, GridViewRowEventArgs e) { if (e.Row.RowType == DataControlRowType.Footer) { DropDownList ddlGrandParent = (DropDownList)e.Row.FindControl("ddlGrandParentService"); ddlGrandParent.DataSource = GetGrandParentService(); ddlGrandParent.DataValueField = "GrandParentServiceID"; ddlGrandParent.DataTextField = "GrandService"; ddlGrandParent.DataBind(); //ddlGrandParent.SelectedValue = GridView1.DataKeys[e.Row.RowIndex].Value.ToString(); DropDownList ddlParent = (DropDownList)e.Row.FindControl("ddlParentService"); //**Getting error "Object reference not set to an instance of an object."** ddlParent.DataSource = GetParentServiceByGrandParent (Convert.ToInt32((GridView1.FooterRow.FindControl("ddlGrandParentService") as DropDownList).SelectedItem.Value)); ddlParent.DataValueField = "ParentServiceId"; ddlParent.DataTextField = "ParentServiceName"; ddlParent.DataBind(); } } private List&lt;GrandParentService&gt; GetGrandParentService() { List&lt;GrandParentService&gt; all = new List&lt;GrandParentService&gt;(); using (HospitalEntities dc = new HospitalEntities()) { all = dc.GrandParentService.ToList(); } return all; } private List&lt;ParentService&gt; GetParentServiceByGrandParent(int grandParentID) { List&lt;ParentService&gt; all = new List&lt;ParentService&gt;(); using (HospitalEntities dc = new HospitalEntities()) { all = dc.ParentService.Where(a =&gt; a.GrandParentServiceID.Equals(grandParentID)).ToList(); } return all; } </code></pre> <p>Please help me. Thanks in advance.</p>
 

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