Xamarin.Forms IOS Value cannot be null. Parameter name: key

Hi,

I cant figure this out:

I don't know if this is the correct aproach, neither the arquitecture. But works on android and let me create pages with less code.

I have what i called 'BaseQueryPage', this inherit from ContentPage.

Inside BaseQueryPage I have this code:

 internal virtual void UpdateLayout(T data)
                {
                    try
                    {
                        if (string.IsNullOrEmpty(data.Error))
                        {
                            DateLabel.Text = GetHttpResponseMessage(data);
                            var layout = new StackLayout()
                            {
                                Padding = new Thickness(5, 0),
                                Children =
                            {
                                CreateTitle(App.StockAccountNumber),
                                //CreateHeader(data),
                                new ScrollView()
                                {
                                    Content = CreateView(data),
                                     VerticalOptions = LayoutOptions.Fill,
                                },
                              //  CreateFooter(data),
                                new StackLayout()
                                {
                                    Orientation = StackOrientation.Horizontal,
                                    HorizontalOptions = LayoutOptions.Fill,
                                    Children =
                                    {
                                        DateLabel,
                                        RefreshButton,
                                        this.FormActivityIndicator
                                    }
                                },
                                ErrorLabel

                            }
                            };
                            Content = layout; // <- This Line pop ups the error

                        }
                        SetErrorMessage(data.Error);
                    }
                    catch (Exception ex)
                    {
                        var a = ex;
                    }

                }

whenever i call any of these methods:
CreateView();
CreateFooter();
CreateHeader();

I get the title error:

Lets, take any of these Functions:

      internal virtual View CreateHeader(T data)
            {
                return null;
            }

On the Actual View:

   internal override View CreateHeader(AccountBriefModel acountBrief)
        {

            var grid = new Grid
            {
                HorizontalOptions = LayoutOptions.FillAndExpand,
                MinimumHeightRequest = 15,
                RowSpacing = 0,
                ColumnSpacing = 0,
                Padding = new Thickness(2)
            };

            grid.Children.Add(CreateLabel("Ticker", TextAlignment.Start, false, Color.White, Color.FromHex(SysVar.GetUI("headerColor"))), 0, 2, 0, 1);
            grid.Children.Add(CreateLabel("Precio", TextAlignment.End, false, Color.White, Color.FromHex(SysVar.GetUI("headerColor"))), 2, 4, 0, 1);
            grid.Children.Add(CreateLabel("Cantidad", TextAlignment.End, false, Color.White, Color.FromHex(SysVar.GetUI("headerColor"))), 4, 6, 0, 1);
            grid.Children.Add(CreateLabel("Monto", TextAlignment.End, false, Color.White, Color.FromHex(SysVar.GetUI("headerColor"))), 6, 9, 0, 1);



            var ly = new StackLayout()
            {
                Orientation = StackOrientation.Vertical,
                HorizontalOptions = LayoutOptions.Fill,
                Children = { grid }
            };

            return ly;
        }

I don't know what I am doing wrong...

The function returns everything ok.

Thanks!

(SstackTrace: " at System.ThrowHelper.ThrowArgumentNullException (ExceptionArgument argument) [0x00000] in /Users/builder/data/lanes/3051/5f11db87/source/maccore/_build/Library/Frameworks/Xamarin.iOS.framework/Versions/git/src/mono/external/referencesource/mscorlib/system/throwhelper.cs:82
at System.Collections.Generic.Dictionary2[TKey,TValue].FindEntry (System.Collections.Generic.TKey key) [0x0000b] in /Users/builder/data/lanes/3051/5f11db87/source/maccore/_build/Library/Frameworks/Xamarin.iOS.framework/Versions/git/src/mono/external/referencesource/mscorlib/system/collections/generic/dictionary.cs:292 at System.Collections.Generic.Dictionary2[TKey,TValue].ContainsKey (System.Collections.Generic.TKey key) [0x00000] in /Users/builder/data/lanes/3051/5f11db87/source/maccore/_build/Library/Frameworks/Xamarin.iOS.framework/Versions/git/src/mono/external/referencesource/mscorlib/system/collections/generic/dictionary.cs:221
at Xamarin.Forms.Platform.iOS.EventTracker.LoadRecognizers () [0x0001e] in :0
at Xamarin.Forms.Platform.iOS.EventTracker.OnElementChanged (System.Object sender, Xamarin.Forms.Platform.iOS.VisualElementChangedEventArgs e) [0x0004e] in :0
at Xamarin.Forms.Platform.iOS.EventTracker.LoadEvents (UIKit.UIView handler) [0x0004e] in :0
at Xamarin.Forms.Platform.iOS.VisualElementRenderer1[TElement].SetElement (Xamarin.Forms.Platform.iOS.TElement element) [0x000f3] in <filename unknown>:0 at Xamarin.Forms.Platform.iOS.VisualElementRenderer1[TElement].Xamarin.Forms.Platform.iOS.IVisualElementRenderer.SetElement (Xamarin.Forms.VisualElement element) [0x00000] in :0
at Xamarin.Forms.Platform.iOS.Platform.CreateRenderer (Xamarin.Forms.VisualElement element) [0x0001b] in :0
at Xamarin.Forms.Platform.iOS.VisualElementPackager.OnChildAdded (Xamarin.Forms.VisualElement view) [0x00000] in :0
at Xamarin.Forms.Platform.iOS.VisualElementPackager.Load () [0x00023] in :0
at Xamarin.Forms.Platform.iOS.VisualElementRenderer1[TElement].SetElement (Xamarin.Forms.Platform.iOS.TElement element) [0x000cc] in <filename unknown>:0 at Xamarin.Forms.Platform.iOS.VisualElementRenderer1[TElement].Xamarin.Forms.Platform.iOS.IVisualElementRenderer.SetElement (Xamarin.Forms.VisualElement element) [0x00000] in :0
at Xamarin.Forms.Platform.iOS.Platform.CreateRenderer (Xamarin.Forms.VisualElement element) [0x0001b] in :0
at Xamarin.Forms.Platform.iOS.VisualElementPackager.OnChildAdded (Xamarin.Forms.VisualElement view) [0x00000] in :0
at Xamarin.Forms.Platform.iOS.VisualElementPackager.Load () [0x00023] in :0
at Xamarin.Forms.Platform.iOS.ScrollViewRenderer.SetElement (Xamarin.Forms.VisualElement element) [0x0008e] in :0
at Xamarin.Forms.Platform.iOS.Platform.CreateRenderer (Xamarin.Forms.VisualElement element) [0x0001b] in :0
at Xamarin.Forms.Platform.iOS.VisualElementPackager.OnChildAdded (Xamarin.Forms.VisualElement view) [0x00000] in :0
at Xamarin.Forms.Platform.iOS.VisualElementPackager.Load () [0x00023] in :0
at Xamarin.Forms.Platform.iOS.VisualElementRenderer1[TElement].SetElement (Xamarin.Forms.Platform.iOS.TElement element) [0x000cc] in <filename unknown>:0 at Xamarin.Forms.Platform.iOS.VisualElementRenderer1[TElement].Xamarin.Forms.Platform.iOS.IVisualElementRenderer.SetElement (Xamarin.Forms.VisualElement element) [0x00000] in :0
at Xamarin.Forms.Platform.iOS.Platform.CreateRenderer (Xamarin.Forms.VisualElement element) [0x0001b] in :0
at Xamarin.Forms.Platform.iOS.VisualElementPackager.OnChildAdded (Xamarin.Forms.VisualElement view) [0x00000] in :0
at Xamarin.Forms.Platform.iOS.VisualElementPackager.OnChildAdded (System.Object sender, Xamarin.Forms.ElementEventArgs e) [0x0000f] in :0
at Xamarin.Forms.Element.OnChildAdded (Xamarin.Forms.Element child) [0x00037] in :0
at Xamarin.Forms.VisualElement.OnChildAdded (Xamarin.Forms.Element child) [0x00000] in :0
at Xamarin.Forms.Page.OnInternalAdded (Xamarin.Forms.VisualElement view) [0x00013] in :0
at Xamarin.Forms.Page.InternalChildrenOnCollectionChanged (System.Object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e) [0x0005f] in :0
at System.Collections.ObjectModel.ObservableCollection1[T].OnCollectionChanged (System.Collections.Specialized.NotifyCollectionChangedEventArgs e) [0x00012] in /Users/builder/data/lanes/3051/5f11db87/source/maccore/_build/Library/Frameworks/Xamarin.iOS.framework/Versions/git/src/mono/external/referencesource/System/compmod/system/collections/objectmodel/observablecollection.cs:286 at System.Collections.ObjectModel.ObservableCollection1[T].OnCollectionChanged (NotifyCollectionChangedAction action, System.Object item, Int32 index) [0x00000] in /Users/builder/data/lanes/3051/5f11db87/source/maccore/_build/Library/Frameworks/Xamarin.iOS.framework/Versions/git/src/mono/external/referencesource/System/compmod/system/collections/objectmodel/observablecollection.cs:349
at System.Collections.ObjectModel.ObservableCollection1[T].InsertItem (Int32 index, System.Collections.ObjectModel.T item) [0x00024] in /Users/builder/data/lanes/3051/5f11db87/source/maccore/_build/Library/Frameworks/Xamarin.iOS.framework/Versions/git/src/mono/external/referencesource/System/compmod/system/collections/objectmodel/observablecollection.cs:217 at System.Collections.ObjectModel.Collection1[T].Add (System.Collections.ObjectModel.T item) [0x00023] in /Users/builder/data/lanes/3051/5f11db87/source/maccore/_build/Library/Frameworks/Xamarin.iOS.framework/Versions/git/src/mono/external/referencesource/mscorlib/system/collections/objectmodel/collection.cs:76
at Xamarin.Forms.ContentPage.set_Content (Xamarin.Forms.View value) [0x00044] in :0
at Gallo.Mobile.UI.BaseHelpers.BaseQueryPage`1[T].UpdateLayout (Gallo.Mobile.UI.BaseHelpers.T data) [0x00112] in c:\Work\Gallo\EstudioGallo\Gallo.Mobile.UI\Gallo.Mobile.UI\BaseHelpers\BaseQueryPage.cs:128 ")