When I start my app on iPhone with a synchronized mac with visual studio 2019, I get the error :

error: * Assertion at ../../../../../mono/metadata/class-init.c:4109, condition `klass' not met

I assume it is related to my page because it crashes at the MainPage = new myPage(); in App.cs.

I can add the whole error print if required.

Any help ?

Edit : a few more informations about the code :

The page's constructor does the following :

• InitializeComponent();
• A database call using WebRequest, StreamWriter, WebResponse
• Uses JObject to parse the anwser and update some Label
• Add Grid to my Layout : The Grid is using : AbsoluteLayout, StackLayout, Frame, TapGestureRecognizer, Image, Button, Label

The xaml :

 <ContentPage.Content>   
        <StackLayout x:Name="stackMainWrapper"
                     BackgroundColor="White">
            <StackLayout x:Name="stackPageHeader"
                         Padding="20,10,20,0" >
                <StackLayout x:Name="stackHeaderNavigation"
                             Orientation="Horizontal">
                    <myApp:SvgIcon x:Name="svgBtnUser" 
                                         ResourceId="myApp.assets.icons.svg.menu.svg" 
                                         WidthRequest="25"
                                         Margin="0,0,10,0"
                                         VerticalOptions="Center">
                        <myApp:SvgIcon.GestureRecognizers>
                            <TapGestureRecognizer Tapped="GoToMenu" />
                        </myApp:SvgIcon.GestureRecognizers>
                    </myApp:SvgIcon>
                    <Label x:Name="labelPageName" 
                               Text=""
                               Style="{StaticResource TitleLabelStyle}"
                               VerticalOptions="Center" />
                    <Button x:Name="btncreate"
                            Text=""
                            Style="{StaticResource ButtonRegularBlue}"
                            Margin="0,10"
                            Clicked=""
                            HorizontalOptions="EndAndExpand"/>
                    <myApp:SvgIcon x:Name="svgBtnFilterResults" 
                                         ResourceId="myApp.assets.icons.svg.search.svg" 
                                         WidthRequest="25"
                                         Margin="10,0,0,0"
                                         CornerRadius="50"
                                         Padding="10,0"
                                         IsVisible="False"
                                         BackgroundColor="{StaticResource LightGreyStyled}"
                                         HorizontalOptions="End"
                                         VerticalOptions="Center">
                        <myApp:SvgIcon.GestureRecognizers>
                            <TapGestureRecognizer
Tapped="BtnFilterResults_Clicked" />
                        </myApp:SvgIcon.GestureRecognizers>
                    </myApp:SvgIcon>
                </StackLayout>

            </StackLayout>
            <controls:ShadowLine />

            <ScrollView x:Name="scrollPageBody"
                        Margin="0">
                <StackLayout x:Name="PageBody"
                         Padding="20" >
                    <Label x:Name="" 
                       Text=""
                       Style="{StaticResource RegularLabelStyle}"
                       HorizontalTextAlignment="Center"
                       Margin="0,0,0,20"/>
                </StackLayout>
            </ScrollView>
        </StackLayout>
    </ContentPage.Content>
</ContentPage>

Edit : Adding the exception trace :

2019-06-13 11:25:52.743 myapp.iOS[682:181626] error: * Assertion at ../../../../../mono/metadata/class-init.c:4109, condition `klass' not met

================================================================= Native Crash Reporting ================================================================= Got a SIGABRT while executing native code. This usually indicates a fatal error in the mono runtime or one of the native libraries used by your

application.

================================================================= Basic Fault Adddress Reporting ================================================================= Memory around native instruction pointer (0x1d3bb20dc):0x1d3bb20cc fd 7b c1 a8 c0 03 5f d6 10 29 80 d2 01 10 00 d4 .{...._..)......

0x1d3bb20dc c3 00 00 54 fd 7b bf a9 fd 03 00 91 55 d6 ff 97 ...T.{......U...

0x1d3bb20ec bf 03 00 91 fd 7b c1 a8 c0 03 5f d6 90 29 80 d2 .....{.. .._..).. 0x1d3bb20fc 01 10 00 d4 c3 00 00 54 fd 7b bf a9 fd 03 00 91 .......T.{.... ..

================================================================= Native stacktrace: ================================================================= 0x1005752fc - /var/containers/Bundle/Application/B332FB94-B5DA-4627-8D03-5471B0CE66FC/myapp.iOS.app/myapp.iOS : (null) 0x10056bc1c - /var/containers/Bundle/Application/B332FB94-B5DA-4627-8D03-5471B0CE66FC/myapp.iOS.app/myapp.iOS : (null) 0x1d3c259ec - /usr/lib/system/libsystem_platform.dylib : 0x1d3c2b094 - /usr/lib/system/libsystem_pthread.dylib : 0x1d3b0bea8 - /usr/lib/system/libsystem_c.dylib : abort 0x1006f1c7c - /var/containers/Bundle/Application/B332FB94-B5DA-4627-8D03-5471B0CE66FC/myapp.iOS.app/myapp.iOS : xamarin_find_protocol_wrapper_type 0x1006d2018 - /var/containers/Bundle/Application/B332FB94-B5DA-4627-8D03-5471B0CE66FC/myapp.iOS.app/myapp.iOS : mono_pmip 0x1006d20a4 - /var/containers/Bundle/Application/B332FB94-B5DA-4627-8D03-5471B0CE66FC/myapp.iOS.app/myapp.iOS : mono_pmip 0x1005adc78 - /var/containers/Bundle/Application/B332FB94-B5DA-4627-8D03-5471B0CE66FC/myapp.iOS.app/myapp.iOS : mono_pmip 0x100713638 - /var/containers/Bundle/Application/B332FB94-B5DA-4627-8D03-5471B0CE66FC/myapp.iOS.app/myapp.iOS : xamarin_ L'exécution de l'application est terminée. localized_string_format_9 0x100710edc - /var/containers/Bundle/Application/B332FB94-B5DA-4627-8D03-5471B0CE66FC/myapp.iOS.app/myapp.iOS : xamarin_localized_string_format_9 0x100702b78 - /var/containers/Bundle/Application/B332FB94-B5DA-4627-8D03-5471B0CE66FC/myapp.iOS.app/myapp.iOS : xamarin_localized_string_format_9 0x100706ad8 - /var/containers/Bundle/Application/B332FB94-B5DA-4627-8D03-5471B0CE66FC/myapp.iOS.app/myapp.iOS : xamarin_localized_string_format_9 0x100706ad8 - /var/containers/Bundle/Application/B332FB94-B5DA-4627-8D03-5471B0CE66FC/myapp.iOS.app/myapp.iOS : xamarin_localized_string_format_9 0x100703a80 - /var/containers/Bundle/Application/B332FB94-B5DA-4627-8D03-5471B0CE66FC/myapp.iOS.app/myapp.iOS : xamarin_localized_string_format_9 0x100701e50 - /var/containers/Bundle/Application/B332FB94-B5DA-4627-8D03-5471B0CE66FC/myapp.iOS.app/myapp.iOS : xamarin_localized_string_format_9 0x10057c294 - /var/containers/Bundle/Applic ation/B332FB94-B5DA-4627-8D03-5471B0CE66FC/myapp.iOS.app/myapp.iOS : mono_pmip 0x10061794c - /var/containers/Bundle/Application/B332FB94-B5DA-4627-8D03-5471B0CE66FC/myapp.iOS.app/myapp.iOS : mono_pmip 0x10061af84 - /var/containers/Bundle/Application/B332FB94-B5DA-4627-8D03-5471B0CE66FC/myapp.iOS.app/myapp.iOS : mono_pmip 0x10047904c - /var/containers/Bundle/Application/B332FB94-B5DA-4627-8D03-5471B0CE66FC/myapp.iOS.app/myapp.iOS : (null) 0x100479844 - /var/containers/Bundle/Application/B332FB94-B5DA-4627-8D03-5471B0CE66FC/myapp.iOS.app/myapp.iOS : (null) 0x2007d0594 - /System/Library/PrivateFrameworks/UIKitCore.framework/UIKitCore : Échec de l'arrêt de l'application : An error occurred on client IDB1610517 while executing a reply for topic xvs/idb/16.1.0.517/stop-app 0x2007d5d20 - /System/Library/PrivateFrameworks/UIKitCore.framework/UIKitCore : 0x2000992dc - /System/Library/PrivateFrameworks/UIKitCore.framework/UIKitCore : L'exécution de l'application est terminée. 0x2000a1874 - /System/Library/PrivateFrameworks/UIKitCore.framework/UIKitCore : 0x200098f60 - /System/Library/PrivateFrameworks/UIKitCore.framework/UIKitCore : 0x200099850 - /System/Library/PrivateFrameworks/UIKitCore.framework/UIKitCore : 0x200097b9c - /System/Library/PrivateFrameworks/UIKitCore.framework/UIKitCore : 0x200097864 - /System/Library/PrivateFrameworks/UIKitCore.framework/UIKitCore : 0x20009c3a4 - /System/Library/PrivateFrameworks/UIKitCore.framework/UIKitCore : 0x20009d188 - /System/Library/PrivateFrameworks/UIKitCore.framework/UIKitCore : _performActionsWithDelayForTransitionContext 0x20009c25c - /System/Library/PrivateFrameworks/UIKitCore.framework/UIKitCore : 0x2007cee30 - /System/Library/PrivateFrameworks/UIKitCore.framework/UIKitCore : 0x2000a0f5c - /System/Library/PrivateFrameworks/UIKitCore.framework/UIKitCore : 0x2007d4328 - /System/Library/PrivateFrameworks/UIKitCore.framework/UIKitCore : 0x2003d0ba8 - /System/Library/PrivateFrameworks/UIKitCore.framework/UIKitCore : 0x1d69909fc - /System/Library/PrivateFrameworks/FrontBoardServices.framework/FrontBoardServices : 0x1d699a40c - /System/Library/PrivateFrameworks/FrontBoardServices.framework/FrontBoardServices : 0x1d6999c14 - /System/Library/PrivateFrameworks/FrontBoardServices.framework/FrontBoardServices : 0x1d3a557d4 - /usr/lib/system/libdispatch.dylib : 0x1d39fa5d8 - /usr/lib/system/libdispatch.dylib : 0x1d69cb040 - /System/Library/PrivateFrameworks/FrontBoardServices.framework/FrontBoardServices : 0x1d69cacdc - /System/Library/PrivateFrameworks/FrontBoardServices.framework/FrontBoardServices : 0x1d69cb294 - /System/Library/PrivateFrameworks/FrontBoardServices.framework/FrontBoardServices : 0x1d3fa7018 - /System/Library/Frameworks/CoreFoundation.framework/CoreFoundation : 0x1d3fa6f98 - /System/Library/Frameworks/CoreFoundation.framework/CoreFoundation : 0x1d3fa6880 - /System/Library/Frameworks/CoreFoundation.framework/CoreFoundation : 0x1d3fa17bc - /System/Library/Frameworks/CoreFoundation.framework/CoreFoundation : 0x1d3fa10b0 - /System/Library/Frameworks/CoreFoundation.framework/CoreFoundation : CFRunLoopRunSpecific 0x1d61a179c - /System/Library/PrivateFrameworks/GraphicsServices.framework/GraphicsServices : GSEventRunModal 0x2007d7978 - /System/Library/PrivateFrameworks/UIKitCore.framework/UIKitCore : UIApplicationMain 0x10071128c - /var/containers/Bundle/Application/B332FB94-B5DA-4627-8D03-5471B0CE66FC/myapp.iOS.app/myapp.iOS : xamarin_localized_string_format_9 0x10070343c - /var/containers/Bundle/Application/B332FB94-B5DA-4627-8D03-5471B0CE66FC/myapp.iOS.app/myapp.iOS : xamarin_localized_string_format_9 0x100703a80 - /var/containers/Bundle/Application/B332FB94-B5DA-4627-8D03-5471B0CE66FC/myapp.iOS.app/myapp.iOS : xamarin_localized_string_format_9 0x100703a80 - /var/containers/Bundle/Application/B332FB94-B5DA-4627-8D03-5471B0CE66FC/myapp.iOS.app/myapp.iOS : xamarin_localized_string_format_9 0x100703a80 - /var/containers/Bundle/Application/B332FB94-B5DA-4627-8D03-5471B0CE66FC/myapp.iOS.app/myapp.iOS : xamarin_localized_string_format_9 0x100703a80 - /var/containers/Bundle/Application/B332FB94-B5DA-4627-8D03-5471B0CE66FC/myapp.iOS.app/myapp.iOS : xamarin_localized_string_format_9 0x100701e50 - /var/containers/Bundle/Application/B332FB94-B5DA-4627-8D03-5471B0CE66FC/myapp.iOS.app/myapp.iOS : xamarin_localized_string_format_9 0x10057c294 - /var/containers/Bundle/Application/B332FB94-B5DA-4627-8D03-5471B0CE66FC/myapp.iOS.app/myapp.iOS : mono_pmip 0x10061794c - /var/containers/Bundle/Application/B332FB94-B5DA-4627-8D03-5471B0CE66FC/enVisit 4> at <0xffffffff> at UIKit.UIApplication:UIApplicationMain <0x000bc> at UIKit.UIApplication:Main <0x0002a> at UIKit.UIApplication:Main <0x0006a> at myapp.iOS.Application:Main <0x00016> at :runtime_invoke_direct_void_string[] <0x00082> ================================================================= e360.iOS.app/myapp.iOS : mono_pmip 0x10061cf68 - /var/containers/Bundle/Application/B332FB94-B5DA-4627-8D03-5471B0CE66FC/myapp.iOS.app/myapp.iOS : mono_pmip 0x100560c64 - /var/containers/Bundle/Application/B332FB94-B5DA-4627-8D03-5471B0CE66FC/myapp.iOS.app/myapp.iOS : (null) 0x100700be0 - /var/containers/Bundle/Application/B332FB94-B5DA-4627-8D03-5471B0CE66FC/myapp.iOS.app/myapp.iOS : xamarin_localized_string_format_9 0x10052adfc - /var/containers/Bundle/Application/B332FB94-B5DA-4627-8D03-5471B0CE66FC/myapp.iOS.app/myapp.iOS : (null) 0x1d3a668e0 - /usr/lib/system/libdyld.dylib :

================================================================= Managed Stacktrace: ================================================================= at <0xffffffff> at myapp.App:.ctor <0x0002c> at myapp.iOS.AppDelegate:FinishedLaunching <0x0006e> at :runtime_invoke_direct_bool__this___UIApplication_NSDictionary <0x000b

You must initialize the page before assigning to mainPage.

MainPage = new myPage();