condition 'klass' not met when loading my page - xamarin.forms

Question

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

Answer 1

I managed to take apart the crashing code, and by uncommenting line after line to see what is breaking, apparently, using dynamic on Xamarin iOS make the app crash.
So well.. avoid using dynamic I guess...

Answer 2

You must initialize the page before assigning to mainPage.
MainPage = new myPage();