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Style applied to a wrong element throws exception in Release but not in Debug
Description
Invalid XAML throws exception in Release but not in Debug. It should be thrown in both or better it should become a compilation error.
The content page below contains a Border
that has a Style="{StaticResource BlackButton}"
.
But the BlackButton
is targetted only at Buttons. This works perfectly fine in Debug but throws an exception in Release. This makes it difficult to spot when you make this mistake.
TestPage.xaml
<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:local="clr-namespace:MauiReleaseXamlBug"
x:Class="MauiReleaseXamlBug.TestPage"
x:DataType="local:TestViewModel"
Title="TestPage">
<Border Style="{StaticResource BlackButton}">
</Border>
</ContentPage>
App.xaml
<Style TargetType="Button" x:Key="BaseButton">
<Setter Property="CornerRadius" Value="25" />
<Setter Property="Padding" Value="20,10,20,10" />
<Setter Property="FontSize" Value="16" />
<Setter Property="HeightRequest" Value="48" />
</Style>
<Style TargetType="Button" x:Key="BlackButton" BasedOn="{StaticResource BaseButton}">
<Setter Property="BackgroundColor" Value="#000000" />
<Setter Property="TextColor" Value="#FFFFFF" />
</Style>
See log output below.
dotnet workload list
Installed Workload Id Manifest Version Installation Source
-------------------------------------------------------------------------------------
maui-windows 8.0.7/8.0.100 VS 17.9.34701.34, VS 17.10.34607.79
android 34.0.79/8.0.100 VS 17.9.34701.34, VS 17.10.34607.79
maccatalyst 17.2.8022/8.0.100 VS 17.9.34701.34, VS 17.10.34607.79
ios 17.2.8022/8.0.100 VS 17.9.34701.34, VS 17.10.34607.79
Steps to Reproduce
- Checkout the attached repository https://github.com/czmirek/MauiReleaseXamlBug
- Run project in Debug
- Click on "Open page"
- Everything works, page opens
- Close project
- Run again in Release
- Exception is thrown --- to avoid the app crashing, the exception is caught and shown in dialog.
Link to public reproduction project repository
https://github.com/czmirek/MauiReleaseXamlBug
Version with bug
Unknown/Other
Is this a regression from previous behavior?
Not sure, did not test other versions
Last version that worked well
Unknown/Other
Affected platforms
iOS, Android
Affected platform versions
Android 14, iOS 17 (iPhone 12)
Did you find any workaround?
Simply fix the style: make duplicate style to target the Border element or remove the style and apply it directly.
Relevant log output
System.InvalidCastException: Arg_InvalidCastException
at Microsoft.Maui.Controls.FontElement.FontSizeDefaultValueCreator(BindableObject bindable)
at Microsoft.Maui.Controls.BindableObject.SetValueCore(BindableProperty property, Object value, SetValueFlags attributes, SetValuePrivateFlags privateAttributes, SetterSpecificity specificity)
at Microsoft.Maui.Controls.BindableObject.SetValue(BindableProperty property, Object value, SetterSpecificity specificity)
at Microsoft.Maui.Controls.Setter.Apply(BindableObject target, SetterSpecificity specificity)
at Microsoft.Maui.Controls.Style.ApplyCore(BindableObject bindable, Style basedOn, SetterSpecificity specificity)
at Microsoft.Maui.Controls.Style.Microsoft.Maui.Controls.IStyle.Apply(BindableObject bindable, SetterSpecificity specificity)
at Microsoft.Maui.Controls.Style.ApplyCore(BindableObject bindable, Style basedOn, SetterSpecificity specificity)
at Microsoft.Maui.Controls.Style.Microsoft.Maui.Controls.IStyle.Apply(BindableObject bindable, SetterSpecificity specificity)
at Microsoft.Maui.Controls.MergedStyle.SetStyle(IStyle implicitStyle, IList`1 classStyles, IStyle style)
at Microsoft.Maui.Controls.MergedStyle.set_Style(IStyle value)
at Microsoft.Maui.Controls.NavigableElement.<>c.<.cctor>b__22_0(BindableObject bindable, Object oldvalue, Object newvalue)
at Microsoft.Maui.Controls.BindableObject.SetValueActual(BindableProperty property, BindablePropertyContext context, Object value, Boolean currentlyApplying, SetValueFlags attributes, SetterSpecificity specificity, Boolean silent)
at Microsoft.Maui.Controls.BindableObject.SetValueCore(BindableProperty property, Object value, SetValueFlags attributes, SetValuePrivateFlags privateAttributes, SetterSpecificity specificity)
at Microsoft.Maui.Controls.BindableObject.SetValue(BindableProperty property, Object value)
at Microsoft.Maui.Controls.NavigableElement.set_Style(Style value)
at MauiReleaseXamlBug.TestPage.InitializeComponent()
at MauiReleaseXamlBug.TestPage..ctor()
at MauiReleaseXamlBug.MainPage.Button_Clicked(Object sender, EventArgs e)
Can repro this issue at Android platform on the latest 17.10 preview 2(8.0.10&8.0.14).
I just had the same problem with a Style
targeted for a Label
type and being applied (accidently) to a VerticalStackLayout
.
Is there not a tool that can walk the XAML and styles and report the errors at compile time?