Sequence contains no elements

[Donna Stewart]

I am using the menu component in a web application written in VB - using VS 2010.  I am getting an InvalidOperationException when the menu is being built that says Sequence contains no elements.  When I debug the menu statement, it goes through the first element in the list then throws the exception.  I can see that my Model has 7 elements, so I am not sure where I am going wrong.  I am fairly new to asp.net so any help is very much appreciated!  Here is my code: 

The View:

<%@ Page Title="" Language="VB" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage(Of IEnumerable (Of gmcps.PublicMenu))" %>

<%@ Import Namespace="gmcps" %>

<asp:Content ID="indexContent" ContentPlaceHolderID="MainContent" runat="server">
    <script type="text/JavaScript">
        window.onload = function () {
            var settings = {
                tl: { radius: 10 },
                tr: { radius: 10 },
                bl: { radius: 10 },
                br: { radius: 10 },
                antiAlias: true
            }

            curvyCorners(settings, "#publicmainleft");
            curvyCorners(settings, "#publicmainright");
            curvyCorners(settings, "#publiccontent");
        }
    </script>

    <%Html.BeginForm()%>
    <div>
        <%= Html.Telerik.Menu() _
            .Name("HomeMenu") _
            .BindTo(Model,
                    Sub(mappings)
                        mappings.For(Of PublicMenu)(
                            Sub(binding)
                                binding _
                                    .ItemDataBound(
                                        Sub(item, publicMenu)
                                            item.Text = publicMenu.mainMenuItem
                                        End Sub) _
                                    .Children(
                                        Function(publicMenu)
                                            Return publicMenu.subMenuItems
                                        End Function)
                            End Sub)
                    End Sub)
        %>
    </div>
    <div id="publiccontent">
        <div class="publiccontentinner">
            <div id="publicmainleft">
                <p class="GMCHomeHeader"><%= Html.lang("HomePageHeader")%><br /></p>
                <p class="GMCHomeContent"><%= Html.lang("HomePageContent")%></p>
            </div>
            <div id="publicmainright">
                <p>
                    <%= Html.SubmitImage("paperless", "/Content/Images/paperless-button.png")%>
                    <%= Html.SubmitImage("findus", "/Content/Images/find-us.png")%>
                    <%= Html.SubmitImage("summit", "/Content/Images/Summit-Button.png")%>
                    <%= Html.SubmitImage("industrynews", "/Content/Images/Industry-news-button.png")%>
                    <%= Html.SubmitImage("certs", "/Content/Images/Certifications-button.png")%>
                </p>
            </div>
        </div>
    </div>
    <%Html.EndForm()%>
</asp:Content>

PublicMenu class:

 

 

 

Public Class PublicMenu

    Public Property mainMenuItem As String
    Public Property subMenuItems As List(Of String)

End Class

Here is the stack trace:
[InvalidOperationException: Sequence contains no elements]
   System.Linq.Enumerable.First(IEnumerable`1 source) +336
   Telerik.Web.Mvc.UI.NavigationItemContainerExtensions.Bind(TNavigationItem component, Object dataItem, NavigationBindingFactory`1 factory) +345
   Telerik.Web.Mvc.UI.NavigationItemContainerExtensions.Bind(TNavigationItem component, Object dataItem, NavigationBindingFactory`1 factory) +651
   Telerik.Web.Mvc.UI.NavigationItemContainerExtensions.BindTo(INavigationItemContainer`1 component, IEnumerable dataSource, Action`1 factoryAction) +384
   Telerik.Web.Mvc.UI.MenuBuilder.BindTo(IEnumerable dataSource, Action`1 factoryAction) +70
   ASP.views_home_index_aspx.__RenderindexContent(HtmlTextWriter __w, Control parameterContainer) in C:\CVS\GMCWeb\gmcps\Views\Home\Index.aspx:30
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +109
   System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +8
   System.Web.UI.Control.Render(HtmlTextWriter writer) +10
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +27
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +100
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +25
   ASP.views_shared_site_master.__Render__control1(HtmlTextWriter __w, Control parameterContainer) in C:\CVS\GMCWeb\gmcps\Views\Shared\Site.Master:3
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +109
   System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +8
   System.Web.UI.Control.Render(HtmlTextWriter writer) +10
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +27
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +100
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +25
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +208
   System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +8
   System.Web.UI.Page.Render(HtmlTextWriter writer) +29
   System.Web.Mvc.ViewPage.Render(HtmlTextWriter writer) +56
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +27
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +100
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +25
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +3060

[Atanas Korchev]

Hi Donna Stewart,

We weren't able to reproduce the problem based on the provided description and code. I suggest you open a support ticket and send us a sample project showing the exception.

Kind regards,
Atanas Korchev
the Telerik team

[Donna Stewart]

I fixed this - I was trying to use strings and list of strings for my menu and submenus.  Maybe this will help someone else who may be as lost as I was on how to use the Telerik MVC menu. 

Here is my view code:

<%@ Page Title="" Language="VB" MasterPageFile="~/Views/Shared/PublicSite.master" Inherits="System.Web.Mvc.ViewPage(Of IEnumerable (Of gmcps.PublicMenu))" %>

<%@ Import Namespace="gmcps" %>

<asp:Content ID="indexContent" ContentPlaceHolderID="MainContent" runat="server">
    <script type="text/JavaScript">
        window.onload = function () {
            var settings = {
                tl: { radius: 10 },
                tr: { radius: 10 },
                bl: { radius: 10 },
                br: { radius: 10 },
                antiAlias: true
            }

            curvyCorners(settings, "#publicmainleft");
            curvyCorners(settings, "#publicmainright");
            curvyCorners(settings, "#publiccontent");
        }
    </script>

    <%Html.BeginForm()%>
    <div>
        <%= Html.Telerik.Menu() _
            .Name("HomeMenu") _
            .BindTo(Model,
                    Sub(mappings)
                        mappings.For(Of PublicMenu)(
                            Sub(binding)
                                binding _
                                    .ItemDataBound(
                                        Sub(item, publicMenu)
                                            item.Text = publicMenu.mainMenuItem.Text
                                            If Not String.IsNullOrWhiteSpace(publicMenu.mainMenuItem.ActionName) Then
                                                item.ActionName = publicMenu.mainMenuItem.ActionName
                                            End If
                                            If Not String.IsNullOrWhiteSpace(publicMenu.mainMenuItem.ControllerName) Then
                                                item.ControllerName = publicMenu.mainMenuItem.ControllerName
                                            End If
                                        End Sub) _
                                    .Children(
                                    Function(publicMenu)
                                        Return publicMenu.subMenuItems
                                    End Function)
                            End Sub)
                        mappings.For(Of Telerik.Web.Mvc.UI.MenuItem)(
                                Sub(binding)
                                    binding.ItemDataBound(
                                        Sub(item, subMenu)
                                            item.Text = subMenu.Text
                                            If Not String.IsNullOrWhiteSpace(subMenu.ActionName) Then
                                                item.ActionName = subMenu.ActionName
                                            End If
                                            If Not String.IsNullOrWhiteSpace(subMenu.ControllerName) Then
                                                item.ControllerName = subMenu.ControllerName
                                            End If
                                        End Sub)
                                End Sub)
                    End Sub)
        %>
    </div>
    <div id="publiccontent">
        <div class="publiccontentinner">
            <div id="publicmainleft">
                <p class="GMCHomeHeader"><%= Html.lang("HomePageHeader")%><br /></p>
                <p class="GMCHomeContent"><%= Html.lang("HomePageContent")%></p>
            </div>
            <div id="publicmainright">
                <p>
                    <%= Html.SubmitImage("paperless", "/Content/Images/paperless-button.png")%>
                    <%= Html.SubmitImage("findus", "/Content/Images/find-us.png")%>
                    <%= Html.SubmitImage("summit", "/Content/Images/Summit-Button.png")%>
                    <%= Html.SubmitImage("industrynews", "/Content/Images/Industry-news-button.png")%>
                    <%= Html.SubmitImage("certs", "/Content/Images/Certifications-button.png")%>
                </p>
            </div>
        </div>
    </div>
    <%Html.EndForm()%>
</asp:Content>

Here is the controller:

Imports System.Resources
Imports gmcps.Utilities

Public Class HomeController
    Inherits System.Web.Mvc.Controller

    Function Index() As ActionResult
        Dim menuList As List(Of PublicMenu) = New List(Of PublicMenu)
        Dim tempList As List(Of ResxItem)
        tempList = GetResXResources("App_GlobalResources\HomePage.resx")
        tempList.Sort()
        Dim prevItem As String = tempList.Item(0).Name
        Dim menuListIndex As Integer = 0
        Dim mmItem As New Telerik.Web.Mvc.UI.MenuItem()
        mmItem.Text = tempList.Item(0).Value
        mmItem.ActionName = "Home"
        mmItem.ControllerName = "Home"
        menuList.Add(New PublicMenu With {.mainMenuItem = mmItem, .subMenuItems = New List(Of Telerik.Web.Mvc.UI.MenuItem)})
        menuList.Item(0).subMenuItems.Add(mmItem)
        For Each tempItem In tempList
            mmItem = New Telerik.Web.Mvc.UI.MenuItem()
            mmItem.ControllerName = "Home"
            mmItem.ActionName = tempItem.Value
            mmItem.Text = tempItem.Value
            If tempList.IndexOf(tempItem) > 0 Then
                If tempItem.Name.Substring(0, 10) = prevItem.Substring(0, 10) Then
                    menuList.Item(menuListIndex).subMenuItems.Add(mmItem)
                Else
                    menuList.Add(New PublicMenu With {.mainMenuItem = mmItem, .subMenuItems = New List(Of Telerik.Web.Mvc.UI.MenuItem)})
                    menuListIndexmenuListIndex = menuListIndex + 1
                    menuList.Item(menuListIndex).subMenuItems.Add(mmItem)
                End If
                prevItem = tempItem.Name
            End If
        Next
        Return (View(menuList))
    End Function

    Function About() As ActionResult
        Return View()
    End Function
End Class

Here is the PublicMenu class:

Public Class PublicMenu

    Public Property mainMenuItem As Telerik.Web.Mvc.UI.MenuItem
    Public Property subMenuItems As List(Of Telerik.Web.Mvc.UI.MenuItem)

End Class

The controller is, of course, not complete, but it shows how I build out the Model for the menu.  This may not be the best way, but it works for what I need.  If anyone has suggestions or comments, feel free...

Oh, and the GetResXResources is something I "borrowed" from Rick Strahl to read a resx file as an xml doc so I could process the menu items.  You can see Rick's blog here - http://www.west-wind.com/weblog/ShowPost.aspx?id=698097.  Thank you, Rick!

Thanks!