Following swipe gesture not fired

<telerikInput:RadCalendar.GestureRecognizers>
               <SwipeGestureRecognizer Swiped="SwipeGestureRecognizer_Swiped" Threshold="10"/>
 </telerikInput:RadCalendar.GestureRecognizers>

when swiping left or right swipe gesture should detect it.

or

when swiping on Multiday calendar add ability to decide swipe how many days back and forth (a property)

 When defining a Date column like

<tdg:DataGridDateColumn PropertyName="ExpiryDate" HeaderText="Expiry"/>

and binding data with a type with Nullable datetime

public System.DateTime? ExpiryDate
{
   get { return _expiryDate; }
   set { SetProperty(ref _expiryDate, value); }
} 

We get an exception

Is there a workaround?

Thanks 

Hello ,

An Admin say me to explain a way to use a QrCode export in PDF .

So what we need ?

I use your RadBarcode to create a barcode so simple . But now this QrCode i want to get him as an imageStream and then use it on a PDFCreator .

For the moment i try to create a view with QrCode -> export this view as an Image -> change that image on ImageStream -> Use this ImageStream on PDfCreator .

I hope you understand me !

Sincerly,

Anthony Ranuuzzi

As the subject:

Before upgrading to the latest version of Telerik Controls, the Drag/Drop functionality worked correctly but after upgrading the list no longer updates and the item moved returns back to the original position.

Not using "ReorderEnded", everything works fine but this is needed to detect that something has been moved. 

Hello!

When include a CheckBox inside a simple ListView (also with RadListView), and try implement the CheckBoxUserCommand Id="IsCheckedChanged" the control appears disabled.

I use MVVM and I need binding the checkedChanged Command to execute a custom operation related to specific row of the ListView; but, how can i know which element of the ListView affecting when checked  / unchecked the CheckBox. Here the code:

PD: Then prefix name of  <checkBoxComamnds:CheckBoxUserCommand>  is wrong, should be <checkBoxCommands: > (Error in word: Comamnds...)

XAML

<AbsoluteLayout BindingContext ="{Binding ViewModel}">      
        <ListView IsRefreshing="{Binding IsRefreshing, Mode=TwoWay}"
                ItemsSource="{Binding CalendarList}">
                <ListView.ItemTemplate>
                    <DataTemplate>
                       <ViewCell>
                            <Grid>
                                <Grid.RowDefinitions >
                                    <RowDefinition Height="Auto"/>
                                </Grid.RowDefinitions>
                                <Grid.ColumnDefinitions>
                                    <ColumnDefinition Width = "Auto" />
                                    <ColumnDefinition Width="*" />
                                </Grid.ColumnDefinitions >
                                 < !--Calendar checkBox Selector -->
                                <telerikPrimitives:RadCheckBox
                                      x:Name="checkViewCalendar">
                                    <telerikPrimitives:RadCheckBox.Commands>
                                        <checkBoxComamnds:CheckBoxUserCommand
                                              Command = "{Binding IsCheckedChangedCommand}"
                                              Id="IsCheckedChanged" 
                                              SuppressDefaultCommand="True">
                                        </checkBoxComamnds:CheckBoxUserCommand>
                                    </telerikPrimitives:RadCheckBox.Commands>
                                </telerikPrimitives:RadCheckBox>
                                <!-- Name of Agenda -->
                                <Label
                                    Grid.Row="0"
                                    Grid.Column="1"
                                    HorizontalOptions="FillAndExpand"
                                    Text="{Binding Name}">
                                </Label>
                           </Grid >
                      </ViewCell >
                   </DataTemplate >
               </ListView.ItemTemplate >
           </ListView >
</AbsoluteLayout>

MVVM Code

namespace ViewModels
{
   //using ...
    using System.Windows.Input;
    using Xamarin.Forms;
    using Telerik.XamarinForms.Primitives.CheckBox.Commands;

    public class CalendarsViewModel : BaseViewModel
        
       public CalendarsViewModel()
        {
            this.IsCheckedChangedCommand = new Command<CheckBoxIsCheckChangedCommandContext>(this.CheckBoxChange);
            this.LoadCalendars();
        }

       private async void CheckBoxChange(CheckBoxIsCheckChangedCommandContext context)
        {
            await Application.Current.MainPage.DisplayAlert(
                    "MVVM Alert Start",
                    $"CheckBox User Command executed at {DateTime.Now.ToLocalTime()} in {context.ToString()}",
                    "Ok");
           //How identify the container row in the context?
        }
        public ICommand IsCheckedChangedCommand { get; set; }

        public ObservableCollection<Calendar> CalendarList
        {
            get { return this.calendars; }
            set { SetValue(ref this.calendars, value); }
        }
        private async void LoadCalendars()
        {
           // API Call to get List and create ObservableCollection Binding to ListView
        }

Currently RadListView  has only pullTorefresh which updates the list if user scrolling the list downwards.. But it is good to have pullUptorefresh kind of gesture. since mostly we need to populate the list when user scrolling up. a gesture direction setting (pullup or down) would do. 

in UWP and using Telerik UI Xamarin R3 2018 got (while Building it):

1>C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Microsoft\VisualStudio\v15.0\AppxPackage\Microsoft.AppXPackage.Targets(1203,5): error MSB3816: Loading assembly "C:\Program Files (x86)\Progress\Telerik UI for Xamarin R3 2018\Binaries\UWP\Telerik.XamarinForms.DataGrid.dll" failed. System.TypeLoadException: Could not load type 'Xamarin.Forms.Xaml.XamlResourceIdAttribute' from assembly 'Xamarin.Forms.Core, Version=2.0.0.0, Culture=neutral, PublicKeyToken=null'.
1>C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Microsoft\VisualStudio\v15.0\AppxPackage\Microsoft.AppXPackage.Targets(1203,5): error MSB3816:    at System.ModuleHandle.ResolveType(RuntimeModule module, Int32 typeToken, IntPtr* typeInstArgs, Int32 typeInstCount, IntPtr* methodInstArgs, Int32 methodInstCount, ObjectHandleOnStack type)
1>C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Microsoft\VisualStudio\v15.0\AppxPackage\Microsoft.AppXPackage.Targets(1203,5): error MSB3816:    at System.ModuleHandle.ResolveTypeHandleInternal(RuntimeModule module, Int32 typeToken, RuntimeTypeHandle[] typeInstantiationContext, RuntimeTypeHandle[] methodInstantiationContext)
1>C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Microsoft\VisualStudio\v15.0\AppxPackage\Microsoft.AppXPackage.Targets(1203,5): error MSB3816:    at System.Reflection.RuntimeModule.ResolveType(Int32 metadataToken, Type[] genericTypeArguments, Type[] genericMethodArguments)
1>C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Microsoft\VisualStudio\v15.0\AppxPackage\Microsoft.AppXPackage.Targets(1203,5): error MSB3816:    at System.Reflection.CustomAttribute.FilterCustomAttributeRecord(CustomAttributeRecord caRecord, MetadataImport scope, Assembly& lastAptcaOkAssembly, RuntimeModule decoratedModule, MetadataToken decoratedToken, RuntimeType attributeFilterType, Boolean mustBeInheritable, Object[] attributes, IList derivedAttributes, RuntimeType& attributeType, IRuntimeMethodInfo& ctor, Boolean& ctorHasParameters, Boolean& isVarArg)
1>C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Microsoft\VisualStudio\v15.0\AppxPackage\Microsoft.AppXPackage.Targets(1203,5): error MSB3816:    at System.Reflection.CustomAttribute.GetCustomAttributes(RuntimeModule decoratedModule, Int32 decoratedMetadataToken, Int32 pcaCount, RuntimeType attributeFilterType, Boolean mustBeInheritable, IList derivedAttributes, Boolean isDecoratedTargetSecurityTransparent)
1>C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Microsoft\VisualStudio\v15.0\AppxPackage\Microsoft.AppXPackage.Targets(1203,5): error MSB3816:    at System.Reflection.CustomAttribute.GetCustomAttributes(RuntimeAssembly assembly, RuntimeType caType)
1>C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Microsoft\VisualStudio\v15.0\AppxPackage\Microsoft.AppXPackage.Targets(1203,5): error MSB3816:    at System.Reflection.RuntimeAssembly.GetCustomAttributes(Type attributeType, Boolean inherit)
1>C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Microsoft\VisualStudio\v15.0\AppxPackage\Microsoft.AppXPackage.Targets(1203,5): error MSB3816:    at System.Attribute.GetCustomAttributes(Assembly element, Type attributeType, Boolean inherit)
1>C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Microsoft\VisualStudio\v15.0\AppxPackage\Microsoft.AppXPackage.Targets(1203,5): error MSB3816:    at System.Attribute.GetCustomAttribute(Assembly element, Type attributeType, Boolean inherit)
1>C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Microsoft\VisualStudio\v15.0\AppxPackage\Microsoft.AppXPackage.Targets(1203,5): error MSB3816:    at System.Reflection.CustomAttributeExtensions.GetCustomAttribute[T](Assembly element)
1>C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Microsoft\VisualStudio\v15.0\AppxPackage\Microsoft.AppXPackage.Targets(1203,5): error MSB3816:    at Microsoft.Build.Tasks.ProcessResourceFiles.ReadAssemblyResources(String name, String outFileOrDir)
1>C:\Program Files (x86)\Progress\Telerik UI for Xamarin R3 2018\Binaries\UWP\Telerik.XamarinForms.DataGrid.dll : error MSB3103: Invalid Resx file. String reference not set to an instance of a String.
1>C:\Program Files (x86)\Progress\Telerik UI for Xamarin R3 2018\Binaries\UWP\Telerik.XamarinForms.DataGrid.dll : error MSB3103: Parameter name: suffix

Tried to find a similar reported issue but none-is-found...

Hello,

If you take a look to the provided screenshot you'll see what's wrong at first sight.

If you add a numeric input belong other kind of input.

You will see that the numeric input is the only one control to have a style which look like the control is being focused.

Current behavior

the NumericInput color is using the accent color for all states. We can't guess whether the control is focused or not.

Expected behavior

the numeric input should have a default color and use the accent color only when focused. Use the default entry style for the entry of the numeric input.

Workaround

you can also expose a numericButtonStyle property or some bindable property to allow us to set the color.

Right now, the control is unusable because of its look. Too bad, the implementation behind is nice.

It was better to create my own control which does the same. I use Telerik to avoid that.

Have a good day and thanks for your attention.

Best regards

Please add an option to center the Xamarin Popup on the page, both horizontally and vertically.   The popup should not move when pickers (and other similar controls) are opened/closed.

Thank you

Hello Telerik Team,

I would like to report a bug I found on Android (not iOS).

If you use a RadCalendar inside a content page which is inside a TabbedPage, you can't swipe on the RadCalendar when it is in ViewMode=Week.

You have to draw a diagonal to make it works otherwise, the swipe (on the RadCalendar) is handled by the TabbedPage and it changes the current page being displayed.

If the RadCalendar ViewMode is set in MultiDay, the Swipe is well handled by the RadCalendar (instead of the TabbedPage).

Expected behavior : swiping on the RadCalendar in ViewMode=Week should change the displayed week (like it does in ViewMode=MultiDay).

Current Behavior : swiping on the RadCalendar in ViewMode=Week should change the selected page of the TabbedPage.

Why I think it is a bug : in ViewMode=MultiDay, the swipe isn't handled the same way : it actually change the displayed day and doesn't change the current page of the TabbedPage control.

PS : if the RadCalendar ViewMode is set to Month, the swipe to change the displayed month is from top to bottom or bottom to top unlike the Week mode which handle swipe from right to left or left to right.

I wish you a happy new year and a lot of bug fix with a lot of new feature released :)

This would allow the user to set advanced Entry properties and layouts.

One such use case was requested:

Set the Entry's MaxLength and add an inline "215/300" to inform the user of how many characters are left for that message. 

When there are more items than can be fit in a horizontal space, allow an opt-in feature to allow horizontal scrolling instead of cutting off the labels

After first appearing on screen, the DataGrid will cause a NullReferenceException when navigating away. Also occurs if you have a DataGrid in a RadTabView and you switch to another tab.

Same code works on UWP, Android. Crashes on iOS.

XAML:

            <tdg:RadDataGrid x:Name="grid"
                             ItemsSource="{Binding Parts}"
                             HorizontalOptions="FillAndExpand" VerticalOptions="FillAndExpand"
                             IsVisible="{Binding ShowData}"
                             StyleClass="TelerikTheme"
                             AlternateRowBackgroundStyle="{StaticResource DefaultDataGridAlternatingRowStyle}"
                             GroupHeaderStyle="{StaticResource DefaultDataGridGroupHeaderStyle}"
                             AutoGenerateColumns="False"
                             SelectionMode="None"
                             UserEditMode="None">
                <tdg:RadDataGrid.Columns>
                    <tdg:DataGridTextColumn PropertyName="PrimaryId"
                                            HeaderText="Primary ID"
                                            CanUserFilter="False"
                                            HeaderStyle="{StaticResource DefaultDataGridColumnHeaderStyle}"
                                            CellContentStyle="{StaticResource DefaultDataGridTextCellStyle}" />
                    <tdg:DataGridTextColumn PropertyName="SecondaryId"
                                            HeaderText="Secondary ID"
                                            CanUserFilter="False"
                                            IsVisible="False"
                                            HeaderStyle="{StaticResource DefaultDataGridColumnHeaderStyle}"
                                            CellContentStyle="{StaticResource DefaultDataGridTextCellStyle}" />
                    <tdg:DataGridDateColumn PropertyName="Start"
                                            HeaderText="Start"
                                            CanUserFilter="False"
                                            CellContentFormat="{}{0:MM/dd/yy hh:mm:ss tt}"
                                            HeaderStyle="{StaticResource DefaultDataGridColumnHeaderStyle}"
                                            CellContentStyle="{StaticResource DefaultDataGridTextCellStyle}" />
                    <tdg:DataGridDateColumn PropertyName="End" 
                                            HeaderText="End" 
                                            CanUserFilter="False"
                                            IsVisible="False"
                                            CellContentFormat="{}{0:MM/dd/yy hh:mm:ss tt}"
                                            HeaderStyle="{StaticResource DefaultDataGridColumnHeaderStyle}"
                                            CellContentStyle="{StaticResource DefaultDataGridTextCellStyle}" />
                    <tdg:DataGridNumericalColumn PropertyName="ShiftNum" 
                                                 HeaderText="Shift #" 
                                                 CanUserFilter="False"
                                                 IsVisible="False"
                                                 HeaderStyle="{StaticResource DefaultDataGridColumnHeaderStyle}"
                                                 CellContentStyle="{StaticResource DefaultDataGridTextCellStyle}" />
                    <tdg:DataGridNumericalColumn PropertyName="ShiftHr" 
                                                 HeaderText="Shift Hour" 
                                                 IsVisible="False"
                                                 HeaderStyle="{StaticResource DefaultDataGridColumnHeaderStyle}"
                                                 CellContentStyle="{StaticResource DefaultDataGridTextCellStyle}" />
                    <tdg:DataGridNumericalColumn PropertyName="ShiftMins" 
                                                 HeaderText="Shift Minutes" 
                                                 CanUserFilter="False"
                                                 IsVisible="False"
                                                 HeaderStyle="{StaticResource DefaultDataGridColumnHeaderStyle}"
                                                 CellContentStyle="{StaticResource DefaultDataGridTextCellStyle}" />
                    <tdg:DataGridTextColumn PropertyName="Line" 
                                            HeaderText="Line" 
                                            CanUserFilter="False"
                                            IsVisible="False"
                                            HeaderStyle="{StaticResource DefaultDataGridColumnHeaderStyle}"
                                            CellContentStyle="{StaticResource DefaultDataGridTextCellStyle}" />
                    <tdg:DataGridTextColumn PropertyName="Station" 
                                            HeaderText="Station"
                                            CanUserFilter="False"
                                            HeaderStyle="{StaticResource DefaultDataGridColumnHeaderStyle}"
                                            CellContentStyle="{StaticResource DefaultDataGridTextCellStyle}" />
                    <tdg:DataGridTextColumn PropertyName="Status" 
                                            HeaderText="Status"
                                            CanUserFilter="False"
                                            HeaderStyle="{StaticResource DefaultDataGridColumnHeaderStyle}"
                                            CellContentStyle="{StaticResource DefaultDataGridTextCellStyle}" />
                    <tdg:DataGridTextColumn PropertyName="Description" 
                                            HeaderText="Description" 
                                            CanUserFilter="False"
                                            IsVisible="False"
                                            HeaderStyle="{StaticResource DefaultDataGridColumnHeaderStyle}"
                                            CellContentStyle="{StaticResource DefaultDataGridTextCellStyle}" />
                </tdg:RadDataGrid.Columns>
            </tdg:RadDataGrid>

Exception:
2018-10-22 14:56:01.776266-0400 Dynimetrics.iOS[9217:125873] 
Unhandled Exception:
System.NullReferenceException: Object reference not set to an instance of an object
  at Xamarin.Forms.Platform.iOS.VisualElementRenderer`1[TElement].UpdateTabStop () [0x00000] in D:\a\1\s\Xamarin.Forms.Platform.iOS\VisualElementRenderer.cs:159 
  at Xamarin.Forms.Platform.iOS.VisualElementRenderer`1[TElement].Xamarin.Forms.Platform.iOS.IVisualElementRenderer.SetElement (Xamarin.Forms.VisualElement element) [0x0000c] in D:\a\1\s\Xamarin.Forms.Platform.iOS\VisualElementRenderer.cs:142 
  at Telerik.XamarinForms.Common.RadPlatform.RetireRenderer (Xamarin.Forms.VisualElement visualElement) [0x0001a] in <854ee8369bca461384d3ac3224bfd96a>:0 
  at Telerik.XamarinForms.Common.iOS.RadViewContainer.ClearContainer () [0x00075] in <854ee8369bca461384d3ac3224bfd96a>:0 
  at Telerik.XamarinForms.Common.iOS.RadViewContainer.Dispose (System.Boolean disposing) [0x0000a] in <854ee8369bca461384d3ac3224bfd96a>:0 
  at Foundation.NSObject.Dispose 
() [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/Foundation/NSObject2.cs:147 
  at Telerik.XamarinForms.PrimitivesRenderer.iOS.ScrollViewRenderer.RetireViewContainer (Telerik.XamarinForms.Common.iOS.RadViewContainer viewContainer) [0x00004] in <c4c4f7bc21d74b21927d9e243e48a659>:0 
  at Telerik.XamarinForms.PrimitivesRenderer.iOS.ScrollViewRenderer.OnElementContentChanged () [0x0000c] in <c4c4f7bc21d74b21927d9e243e48a659>:0 
  at Telerik.XamarinForms.PrimitivesRenderer.iOS.ScrollViewRenderer.OnElementDetached (Telerik.XamarinForms.Primitives.RadScrollView oldElement) [0x00032] in <c4c4f7bc21d74b21927d9e243e48a659>:0 
  at Telerik.XamarinForms.Common.iOS.IosRendererBase`2[S,T].OnElementChanged (Xamarin.Forms.Platform.iOS.ElementChangedEventArgs`1[TElement] e) [0x00016] in <854ee8369bca461384d3ac3224bfd96a>:0 
  at Xamarin.Forms.Platform.iOS.VisualElementRenderer`1[TElement].SetElement (TElement element) [0x00122] in D:\a\1\s\Xamarin.Forms.Platform.iOS\VisualElementRen
derer.cs:259 
  at Xamarin.Forms.Platform.iOS.VisualElementRenderer`1[TElement].Dispose (System.Boolean disposing) [0x0008c] in D:\a\1\s\Xamarin.Forms.Platform.iOS\VisualElementRenderer.cs:340 
  at Xamarin.Forms.Platform.iOS.ViewRenderer`2[TView,TNativeView].Dispose (System.Boolean disposing) [0x00000] in D:\a\1\s\Xamarin.Forms.Platform.iOS\ViewRenderer.cs:84 
  at Foundation.NSObject.Dispose () [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/Foundation/NSObject2.cs:147 
  at Xamarin.Forms.Platform.iOS.VisualElementPackager.Dispose (System.Boolean disposing) [0x0003f] in D:\a\1\s\Xamarin.Forms.Platform.iOS\VisualElementPackager.cs:69 
  at Xamarin.Forms.Platform.iOS.VisualElementPackager.Dispose () [0x00000] in D:\a\1\s\Xamarin.Forms.Platform.iOS\VisualElementPackager.cs:37 
  at Xamarin.Forms.Platform.iOS.VisualElementRenderer`1[TElement].Dispose (System.Boolean disposing) [0x00058] in D:\a\1\s\Xamarin.Forms.Platform.iOS\VisualElementRenderer.cs:331 
  at Foundation
.NSObject.Dispose () [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/Foundation/NSObject2.cs:147 
  at Xamarin.Forms.Platform.iOS.VisualElementPackager.Dispose (System.Boolean disposing) [0x0003f] in D:\a\1\s\Xamarin.Forms.Platform.iOS\VisualElementPackager.cs:69 
  at Xamarin.Forms.Platform.iOS.VisualElementPackager.Dispose () [0x00000] in D:\a\1\s\Xamarin.Forms.Platform.iOS\VisualElementPackager.cs:37 
  at Xamarin.Forms.Platform.iOS.VisualElementRenderer`1[TElement].Dispose (System.Boolean disposing) [0x00058] in D:\a\1\s\Xamarin.Forms.Platform.iOS\VisualElementRenderer.cs:331 
  at Foundation.NSObject.Dispose () [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/Foundation/NSObject2.cs:147 
  at Xamarin.Forms.Platform.iOS.VisualElementPackager.Dispose (System.Boolean disposing) [0x0003f] in D:\a\1\s\Xamarin.Forms.Platform.iOS\VisualElementPackager.cs:69 
  at Xamarin.Forms.Platform.iOS.VisualElementPackager.Dispose () [0x0000
0] in D:\a\1\s\Xamarin.Forms.Platform.iOS\VisualElementPackager.cs:37 
  at Xamarin.Forms.Platform.iOS.PageRenderer.Dispose (System.Boolean disposing) [0x00070] in D:\a\1\s\Xamarin.Forms.Platform.iOS\Renderers\PageRenderer.cs:164 
  at Foundation.NSObject.Dispose () [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/Foundation/NSObject2.cs:147 
  at Xamarin.Forms.Platform.iOS.DisposeHelpers.DisposeModalAndChildRenderers (Xamarin.Forms.Element view) [0x00038] in D:\a\1\s\Xamarin.Forms.Platform.iOS\DisposeHelpers.cs:17 
  at Xamarin.Forms.Platform.iOS.Platform.HandleChildRemoved (System.Object sender, Xamarin.Forms.ElementEventArgs e) [0x00006] in D:\a\1\s\Xamarin.Forms.Platform.iOS\Platform.cs:297 
  at Xamarin.Forms.Element.OnDescendantRemoved (Xamarin.Forms.Element child) [0x00000] in D:\a\1\s\Xamarin.Forms.Core\Element.cs:617 
  at Xamarin.Forms.Element.OnChildRemoved (Xamarin.Forms.Element child) [0x0001f] in D:\a\1\s\Xamarin.Forms.Core\Element.cs:357 
  at Xamarin.Fo
rms.VisualElement.OnChildRemoved (Xamarin.Forms.Element child) [0x00000] in D:\a\1\s\Xamarin.Forms.Core\VisualElement.cs:748 
  at Xamarin.Forms.Page.OnInternalRemoved (Xamarin.Forms.VisualElement view) [0x00013] in D:\a\1\s\Xamarin.Forms.Core\Page.cs:380 
  at Xamarin.Forms.Page.InternalChildrenOnCollectionChanged (System.Object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e) [0x00022] in D:\a\1\s\Xamarin.Forms.Core\Page.cs:358 
  at System.Collections.ObjectModel.ObservableCollection`1[T].OnCollectionChanged (System.Collections.Specialized.NotifyCollectionChangedEventArgs e) [0x0000f] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/System/compmod/system/collections/objectmodel/observablecollection.cs:288 
  at System.Collections.ObjectModel.ObservableCollection`1[T].OnCollectionChanged (System.Collections.Specialized.NotifyCollectionChangedAction action, System.Object item, System.Int32 index) [0x00000] in /Library/Framewor
ks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/System/compmod/system/collections/objectmodel/observablecollection.cs:351 
  at System.Collections.ObjectModel.ObservableCollection`1[T].RemoveItem (System.Int32 index) [0x0002b] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/System/compmod/system/collections/objectmodel/observablecollection.cs:205 
  at System.Collections.ObjectModel.Collection`1[T].Remove (T item) [0x00027] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/mscorlib/system/collections/objectmodel/collection.cs:113 
  at Xamarin.Forms.MasterDetailPage.set_Detail (Xamarin.Forms.Page value) [0x0004b] in D:\a\1\s\Xamarin.Forms.Core\MasterDetailPage.cs:44 
  at Dynimetrics.UI.Views.MainPage+<NavigateFromMenu>d__6.MoveNext () [0x0006f] in C:\src\PlantFloorConnect\Dynimetrics\Dynimetrics.UI\Views\MainPage.xaml.cs:54 
--- End of stack trace from previo
us location where exception was thrown ---
  at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x00037] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:187 
  at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0x00028] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:156 
  at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x00008] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:128 
  at System.Runtime.CompilerServices.TaskAwaiter.GetResult () [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/1
2.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:113 
  at Dynimetrics.UI.Views.MenuPage+<<-ctor>b__3_0>d.MoveNext () [0x0005d] in C:\src\PlantFloorConnect\Dynimetrics\Dynimetrics.UI\Views\MenuPage.xaml.cs:54 
--- End of stack trace from previous location where exception was thrown ---
  at System.Runtime.CompilerServices.AsyncMethodBuilderCore+<>c.<ThrowAsync>b__6_0 (System.Object state) [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:1018 
  at Foundation.NSAsyncSynchronizationContextDispatcher.Apply () [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/Foundation/NSAction.cs:178 
--- End of stack trace from previous location where exception was thrown ---
  at (wrapper managed-to-native) UIKit.UIApplication.UIApplicationMain(int,string[],intptr,intptr)
  at UIKit.UIApplication.Main 
(System.String[] args, System.IntPtr principal, System.IntPtr delegate) [0x00005] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/UIKit/UIApplication.cs:79 
  at UIKit.UIApplication.Main (System.String[] args, System.String principalClassName, System.String delegateClassName) [0x0002c] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/UIKit/UIApplication.cs:63 
  at Dynimetrics.iOS.Application.Main (System.String[] args) [0x00001] in C:\src\PlantFloorConnect\Dynimetrics\Dynimetrics.UI.iOS\Main.cs:17
2018-10-22 14:56:01.780638-0400 Dynimetrics.iOS[9217:125873] Unhandled managed exception:
Object reference not set to an instance of an object (System.NullReferenceException)
  at Xamarin.Forms.Platform.iOS.VisualElementRenderer`1[TElement].UpdateTabStop () [0x00000] in D:\a\1\s\Xamarin.Forms.Platform.iOS\VisualElementRenderer.cs:159 
  at Xamarin.Forms.Platform.iOS.VisualElementRenderer`1[TElement].Xamarin.Forms.Platform.iOS.IVisualElementRenderer.SetE
lement (Xamarin.Forms.VisualElement element) [0x0000c] in D:\a\1\s\Xamarin.Forms.Platform.iOS\VisualElementRenderer.cs:142 
  at Telerik.XamarinForms.Common.RadPlatform.RetireRenderer (Xamarin.Forms.VisualElement visualElement) [0x0001a] in <854ee8369bca461384d3ac3224bfd96a>:0 
  at Telerik.XamarinForms.Common.iOS.RadViewContainer.ClearContainer () [0x00075] in <854ee8369bca461384d3ac3224bfd96a>:0 
  at Telerik.XamarinForms.Common.iOS.RadViewContainer.Dispose (System.Boolean disposing) [0x0000a] in <854ee8369bca461384d3ac3224bfd96a>:0 
  at Foundation.NSObject.Dispose () [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/Foundation/NSObject2.cs:147 
  at Telerik.XamarinForms.PrimitivesRenderer.iOS.ScrollViewRenderer.RetireViewContainer (Telerik.XamarinForms.Common.iOS.RadViewContainer viewContainer) [0x00004] in <c4c4f7bc21d74b21927d9e243e48a659>:0 
  at Telerik.XamarinForms.PrimitivesRenderer.iOS.ScrollViewRenderer.OnElementContentChanged () [0x0000c] in <c4c4f7bc21d74b
21927d9e243e48a659>:0 
  at Telerik.XamarinForms.PrimitivesRenderer.iOS.ScrollViewRenderer.OnElementDetached (Telerik.XamarinForms.Primitives.RadScrollView oldElement) [0x00032] in <c4c4f7bc21d74b21927d9e243e48a659>:0 
  at Telerik.XamarinForms.Common.iOS.IosRendererBase`2[S,T].OnElementChanged (Xamarin.Forms.Platform.iOS.ElementChangedEventArgs`1[TElement] e) [0x00016] in <854ee8369bca461384d3ac3224bfd96a>:0 
  at Xamarin.Forms.Platform.iOS.VisualElementRenderer`1[TElement].SetElement (TElement element) [0x00122] in D:\a\1\s\Xamarin.Forms.Platform.iOS\VisualElementRenderer.cs:259 
  at Xamarin.Forms.Platform.iOS.VisualElementRenderer`1[TElement].Dispose (System.Boolean disposing) [0x0008c] in D:\a\1\s\Xamarin.Forms.Platform.iOS\VisualElementRenderer.cs:340 
  at Xamarin.Forms.Platform.iOS.ViewRenderer`2[TView,TNativeView].Dispose (System.Boolean disposing) [0x00000] in D:\a\1\s\Xamarin.Forms.Platform.iOS\ViewRenderer.cs:84 
  at Foundation.NSObject.Dispose () [0x00000] in /Library/Frameworks/Xamarin.iOS.fram
ework/Versions/12.0.0.15/src/Xamarin.iOS/Foundation/NSObject2.cs:147 
  at Xamarin.Forms.Platform.iOS.VisualElementPackager.Dispose (System.Boolean disposing) [0x0003f] in D:\a\1\s\Xamarin.Forms.Platform.iOS\VisualElementPackager.cs:69 
  at Xamarin.Forms.Platform.iOS.VisualElementPackager.Dispose () [0x00000] in D:\a\1\s\Xamarin.Forms.Platform.iOS\VisualElementPackager.cs:37 
  at Xamarin.Forms.Platform.iOS.VisualElementRenderer`1[TElement].Dispose (System.Boolean disposing) [0x00058] in D:\a\1\s\Xamarin.Forms.Platform.iOS\VisualElementRenderer.cs:331 
  at Foundation.NSObject.Dispose () [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/Foundation/NSObject2.cs:147 
  at Xamarin.Forms.Platform.iOS.VisualElementPackager.Dispose (System.Boolean disposing) [0x0003f] in D:\a\1\s\Xamarin.Forms.Platform.iOS\VisualElementPackager.cs:69 
  at Xamarin.Forms.Platform.iOS.VisualElementPackager.Dispose () [0x00000] in D:\a\1\s\Xamarin.Forms.Platform.iOS\VisualElementPackager.cs:37 

  at Xamarin.Forms.Platform.iOS.VisualElementRenderer`1[TElement].Dispose (System.Boolean disposing) [0x00058] in D:\a\1\s\Xamarin.Forms.Platform.iOS\VisualElementRenderer.cs:331 
  at Foundation.NSObject.Dispose () [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/Foundation/NSObject2.cs:147 
  at Xamarin.Forms.Platform.iOS.VisualElementPackager.Dispose (System.Boolean disposing) [0x0003f] in D:\a\1\s\Xamarin.Forms.Platform.iOS\VisualElementPackager.cs:69 
  at Xamarin.Forms.Platform.iOS.VisualElementPackager.Dispose () [0x00000] in D:\a\1\s\Xamarin.Forms.Platform.iOS\VisualElementPackager.cs:37 
  at Xamarin.Forms.Platform.iOS.PageRenderer.Dispose (System.Boolean disposing) [0x00070] in D:\a\1\s\Xamarin.Forms.Platform.iOS\Renderers\PageRenderer.cs:164 
  at Foundation.NSObject.Dispose () [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/Foundation/NSObject2.cs:147 
  at Xamarin.Forms.Platform.iOS.DisposeHelpers.DisposeModalAndC
hildRenderers (Xamarin.Forms.Element view) [0x00038] in D:\a\1\s\Xamarin.Forms.Platform.iOS\DisposeHelpers.cs:17 
  at Xamarin.Forms.Platform.iOS.Platform.HandleChildRemoved (System.Object sender, Xamarin.Forms.ElementEventArgs e) [0x00006] in D:\a\1\s\Xamarin.Forms.Platform.iOS\Platform.cs:297 
  at Xamarin.Forms.Element.OnDescendantRemoved (Xamarin.Forms.Element child) [0x00000] in D:\a\1\s\Xamarin.Forms.Core\Element.cs:617 
  at Xamarin.Forms.Element.OnChildRemoved (Xamarin.Forms.Element child) [0x0001f] in D:\a\1\s\Xamarin.Forms.Core\Element.cs:357 
  at Xamarin.Forms.VisualElement.OnChildRemoved (Xamarin.Forms.Element child) [0x00000] in D:\a\1\s\Xamarin.Forms.Core\VisualElement.cs:748 
  at Xamarin.Forms.Page.OnInternalRemoved (Xamarin.Forms.VisualElement view) [0x00013] in D:\a\1\s\Xamarin.Forms.Core\Page.cs:380 
  at Xamarin.Forms.Page.InternalChildrenOnCollectionChanged (System.Object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e) [0x00022] in D:\a\1\s\Xamarin.Forms.Core\P
age.cs:358 
  at System.Collections.ObjectModel.ObservableCollection`1[T].OnCollectionChanged (System.Collections.Specialized.NotifyCollectionChangedEventArgs e) [0x0000f] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/System/compmod/system/collections/objectmodel/observablecollection.cs:288 
  at System.Collections.ObjectModel.ObservableCollection`1[T].OnCollectionChanged (System.Collections.Specialized.NotifyCollectionChangedAction action, System.Object item, System.Int32 index) [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/System/compmod/system/collections/objectmodel/observablecollection.cs:351 
  at System.Collections.ObjectModel.ObservableCollection`1[T].RemoveItem (System.Int32 index) [0x0002b] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/System/compmod/system/collections/objectmodel/observablecollection.cs:205 
  a
t System.Collections.ObjectModel.Collection`1[T].Remove (T item) [0x00027] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/mscorlib/system/collections/objectmodel/collection.cs:113 
  at Xamarin.Forms.MasterDetailPage.set_Detail (Xamarin.Forms.Page value) [0x0004b] in D:\a\1\s\Xamarin.Forms.Core\MasterDetailPage.cs:44 
  at Dynimetrics.UI.Views.MainPage+<NavigateFromMenu>d__6.MoveNext () [0x0006f] in C:\src\PlantFloorConnect\Dynimetrics\Dynimetrics.UI\Views\MainPage.xaml.cs:54 
--- End of stack trace from previous location where exception was thrown ---
  at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x00037] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:187 
  at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0
x00028] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:156 
  at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x00008] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:128 
  at System.Runtime.CompilerServices.TaskAwaiter.GetResult () [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:113 
  at Dynimetrics.UI.Views.MenuPage+<<-ctor>b__3_0>d.MoveNext () [0x0005d] in C:\src\PlantFloorConnect\Dynimetrics\Dynimetrics.UI\Views\MenuPage.xaml.cs:54 
--- End of stack trace from previous location where exception was thrown ---
  at System.Runtime.CompilerServices.AsyncMethodBuilderCore+<>c.<ThrowAsync>b__6_0 (System.Object state)
 [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:1018 
  at Foundation.NSAsyncSynchronizationContextDispatcher.Apply () [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/Foundation/NSAction.cs:178 
--- End of stack trace from previous location where exception was thrown ---
  at (wrapper managed-to-native) UIKit.UIApplication.UIApplicationMain(int,string[],intptr,intptr)
  at UIKit.UIApplication.Main (System.String[] args, System.IntPtr principal, System.IntPtr delegate) [0x00005] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/UIKit/UIApplication.cs:79 
  at UIKit.UIApplication.Main (System.String[] args, System.String principalClassName, System.String delegateClassName) [0x0002c] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/UIKit/UIApplication.cs:63 
  at Dynimetrics.iOS.Ap
plication.Main (System.String[] args) [0x00001] in C:\src\PlantFloorConnect\Dynimetrics\Dynimetrics.UI.iOS\Main.cs:17

Xamarin.Forms library that allows to have for Google-Map-Like sliding panel from bottom of the screen. 

I have a RadLegend that is within a portion of the UI that has its visibility toggled with IsVisible. The logical tree is as follows (it's a custom styled tab UI):

MasterDetailPage -> Detail -> ContentPage -> StackLayout -> Grid (IsVisible bound to "ShowData") -> StackLayout (IsVisible bound to "ShowCategoryData") -> StackLayout -> RadLegend

Sometimes it's visible, sometimes it disappears after one of its parent control's visibility changes, sometimes it reappears. Not sure what the rhyme or reason is on when it happens. Seems to happen more on iOS than on Android, but I've seen it happen on both.

Full XAML for the page it happens on is attached.

When you work with mobile one of the major issues I have found is that the picker does not allow filtering so when you have more than a hundred of items the user can select on but you are displaying a thousand it’s kind of complicated, so a filtered picker would be awesome for developers that are working with Telerik controls