Fix XamlParseException: StaticResource not found for key Gray400

[Copilot]

• Fix App.xaml to load Colors.xaml before LightTheme.xaml
• Fix LightTheme.xaml MergedDictionaries path — use Colors.xaml (sibling path) instead of Resources/Styles/Colors.xaml (which produced a doubled-up path error)

Original prompt

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This section details on the original issue you should resolve

<issue_title>Login Screen Revamp</issue_title>
<issue_description>Revamp the login screen to a more modern looking layout, use guidance from the parent issue for finer details</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Login Screen Revamp #463

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[StuartFerguson]

@copilot get this error running app locally

Exception thrown: 'Microsoft.Maui.Controls.Xaml.XamlParseException' in System.Private.CoreLib.dll
03-04 18:33:57.988 E/AndroidRuntime(19109): FATAL EXCEPTION: main
03-04 18:33:57.988 E/AndroidRuntime(19109): Process: com.transactionprocessor.mobile, PID: 19109
03-04 18:33:57.988 E/AndroidRuntime(19109): android.runtime.JavaProxyThrowable: [Microsoft.Maui.Controls.Xaml.XamlParseException]: Position 226:45. StaticResource not found for key Gray400
03-04 18:33:57.988 E/AndroidRuntime(19109): at Microsoft.Maui.Controls.Xaml.ApplyPropertiesVisitor.ProvideValue(//src/Controls/src/Xaml/ApplyPropertiesVisitor.cs:287)
03-04 18:33:57.988 E/AndroidRuntime(19109): at Microsoft.Maui.Controls.Xaml.ApplyPropertiesVisitor.Visit(//src/Controls/src/Xaml/ApplyPropertiesVisitor.cs:127)
03-04 18:33:57.988 E/AndroidRuntime(19109): at Microsoft.Maui.Controls.Xaml.ElementNode.Accept(//src/Controls/src/Xaml/XamlNode.cs:128)
03-04 18:33:57.988 E/AndroidRuntime(19109): at Microsoft.Maui.Controls.Xaml.ElementNode.Accept(//src/Controls/src/Xaml/XamlNode.cs:122)
03-04 18:33:57.988 E/AndroidRuntime(19109): at Microsoft.Maui.Controls.Xaml.ElementNode.Accept(//src/Controls/src/Xaml/XamlNode.cs:124)
03-04 18:33:57.988 E/AndroidRuntime(19109): at Microsoft.Maui.Controls.Xaml.FillResourceDictionariesVisitor.Visit(//src/Controls/src/Xaml/FillResourceDictionariesVisitor.cs:62)
03-04 18:33:57.988 E/AndroidRuntime(19109): at Microsoft.Maui.Controls.Xaml.ElementNode.Accept(//src/Controls/src/Xaml/XamlNode.cs:117)
03-04 18:33:57.988 E/AndroidRuntime(19109): at Microsoft.Maui.Controls.Xaml.RootNode.Accept(//src/Controls/src/Xaml/XamlNode.cs:179)
03-04 18:33:57.988 E/AndroidRuntime(19109): at Microsoft.Maui.Controls.Xaml.XamlLoader.Visit(//src/Controls/src/Xaml/XamlLoader.cs:236)
03-04 18:33:57.988 E/AndroidRuntime(19109): at Microsoft.Maui.Controls.Xaml.XamlLoader.Load(//src/Controls/src/Xaml/XamlLoader.cs:103)
03-04 18:33:57.988 E/AndroidRuntime(19109): at Microsoft.Maui.Controls.Xaml.XamlLoader.Load(//src/Controls/src/Xaml/XamlLoader.cs:57)
03-04 18:33:57.988 E/AndroidRuntime(19109): at Microsoft.Maui.Controls.Xaml.XamlLoader.Load(//src/Controls/src/Xaml/XamlLoader.cs:53)
03-04 18:33:57.988 E/AndroidRuntime(19109): at Microsoft.Maui.Controls.Xaml.Extensions.LoadFromXaml(//src/Controls/src/Xaml/ViewExtensions.cs:42)
03-04 18:33:57.988 E/AndroidRuntime(19109): at TransactionProcessor.Mobile.Resources.Styles.LightTheme.InitializeComponent(C:\Projects\TransactionProcessing\TransactionMobile\TransactionProcessor.Mobile\obj\Debug
et10.0-android\Microsoft.Maui.Controls.SourceGen\Microsoft.Maui.Controls.SourceGen.XamlGenerator\Resources_Styles_LightTheme.xaml.sg.cs:20)
03-04 18:33:57.988 E/AndroidRuntime(19109): at TransactionProcessor.Mobile.Resources.Styles.LightTheme..ctor(C:\Projects\TransactionProcessing\TransactionMobile\TransactionProcessor.Mobile\Resources\Styles\LightTheme.xaml.cs:7)
03-04 18:33:57.988 E/AndroidRuntime(19109): at Unknown.Unknown(Unknown Source)
03-04 18:33:57.988 E/AndroidRuntime(19109): at System.Reflection.MethodBaseInvoker.InterpretedInvoke_Constructor + 0x0(Unknown Source)
03-04 18:33:57.988 E/AndroidRuntime(19109): at System.Reflection.MethodBaseInvoker.InvokeWithNoArgs + 0x24(Unknown Source)
03-04 18:33:57.988 E/AndroidRuntime(19109): at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw + 0x11(Unknown Source)
03-04 18:33:57.988 E/AndroidRuntime(19109): at Microsoft.Maui.Controls.ResourceDictionary+<>c__DisplayClass11_0.b__0(//src/Controls/src/Core/ResourceDictionary.cs:89)
03-04 18:33:57.988 E/AndroidRuntime(19109): at System.Runtime.CompilerServices.ConditionalWeakTable2[[System.Type, System.Private.CoreLib, Version=10.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[Microsoft.Maui.Controls.ResourceDictionary, Microsoft.Maui.Controls, Version=10.0.0.0, Culture=neutral, PublicKeyToken=null]].GetValue + 0x18(Unknown Source) 03-04 18:33:57.988 E/AndroidRuntime(19109): at Microsoft.Maui.Controls.ResourceDictionary.GetOrCreateInstance(/_/src/Controls/src/Core/ResourceDictionary.cs:81) 03-04 18:33:57.988 E/AndroidRuntime(19109): at Microsoft.Maui.Controls.Xaml.ResourceDictionaryHelpers.SetAndLoadSource(/_/src/Controls/src/Xaml/ResourceDictionaryHelpers.cs:42) 03-04 18:33:57.988 E/AndroidRuntime(19109): at Microsoft.Maui.Controls.Xaml.ResourceDictionaryHelpers.LoadFromSource(/_/src/Controls/src/Xaml/ResourceDictionaryHelpers.cs:35) 03-04 18:33:57.988 E/AndroidRuntime(19109): at Microsoft.Maui.Controls.Xaml.ApplyPropertiesVisitor.SetPropertyValue(/_/src/Controls/src/Xaml/ApplyPropertiesVisitor.cs:357) 03-04 18:33:57.988 E/AndroidRuntime(19109): at Microsoft.Maui.Controls.Xaml.ApplyPropertiesVisitor.Visit(/_/src/Controls/src/Xaml/ApplyPropertiesVisitor.cs:70) 03-04 18:33:57.988 E/AndroidRuntime(19109): at Microsoft.Maui.Controls.Xaml.ValueNode.Accept(/_/src/Controls/src/Xaml/XamlNode.cs:55) 03-04 18:33:57.988 E/AndroidRuntime(19109): at Microsoft.Maui.Controls.Xaml.FillResourceDictionariesVisitor.Visit(/_/src/Controls/src/Xaml/FillResourceDictionariesVisitor.cs:33) 03-04 18:33:57.988 E/AndroidRuntime(19109): at Microsoft.Maui.Controls.Xaml.ValueNode.Accept(/_/src/Controls/src/Xaml/XamlNode.cs:55) 03-04 18:33:57.988 E/AndroidRuntime(19109): at Microsoft.Maui.Controls.Xaml.ElementNode.Accept(/_/src/Controls/src/Xaml/XamlNode.cs:122) 03-04 18:33:57.988 E/AndroidRuntime(19109): at Microsoft.Maui.Controls.Xaml.RootNode.Accept(/_/src/Controls/src/Xaml/XamlNode.cs:177) 03-04 18:33:57.996 E/AndroidRuntime(19109): at Microsoft.Maui.Controls.Xaml.XamlLoader.Visit(/_/src/Controls/src/Xaml/XamlLoader.cs:236) 03-04 18:33:57.996 E/AndroidRuntime(19109): at Microsoft.Maui.Controls.Xaml.XamlLoader.Load(/_/src/Controls/src/Xaml/XamlLoader.cs:103) 03-04 18:33:57.996 E/AndroidRuntime(19109): at Microsoft.Maui.Controls.Xaml.XamlLoader.Load(/_/src/Controls/src/Xaml/XamlLoader.cs:57) 03-04 18:33:57.996 E/AndroidRuntime(19109): at Microsoft.Maui.Controls.Xaml.XamlLoader.Load(/_/src/Controls/src/Xaml/XamlLoader.cs:53) 03-04 18:33:57.996 E/AndroidRuntime(19109): at Microsoft.Maui.Controls.Xaml.Extensions.LoadFromXaml(/_/src/Controls/src/Xaml/ViewExtensions.cs:42) 03-04 18:33:57.996 E/AndroidRuntime(19109): at TransactionProcessor.Mobile.App.InitializeComponent(C:\Projects\TransactionProcessing\TransactionMobile\TransactionProcessor.Mobile\obj\Debug et10.0-android\Microsoft.Maui.Controls.SourceGen\Microsoft.Maui.Controls.SourceGen.XamlGenerator\App.xaml.sg.cs:20) 03-04 18:33:57.996 E/AndroidRuntime(19109): at TransactionProcessor.Mobile.App..ctor(C:\Projects\TransactionProcessing\TransactionMobile\TransactionProcessor.Mobile\App.xaml.cs:52) 03-04 18:33:57.996 E/AndroidRuntime(19109): at Unknown.Unknown(Unknown Source) 03-04 18:33:57.996 E/AndroidRuntime(19109): at System.Reflection.MethodBaseInvoker.InterpretedInvoke_Constructor + 0x0(Unknown Source) 03-04 18:33:57.996 E/AndroidRuntime(19109): at System.Reflection.MethodBaseInvoker.InvokeWithNoArgs + 0x24(Unknown Source) 03-04 18:33:57.996 E/AndroidRuntime(19109): at System.Reflection.RuntimeConstructorInfo.Invoke + 0x4a(Unknown Source) 03-04 18:33:57.996 E/AndroidRuntime(19109): at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor + 0x3f(Unknown Source) 03-04 18:33:57.996 E/AndroidRuntime(19109): at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor2[[Microsoft.Extensions.DependencyInjection.ServiceLookup.RuntimeResolverContext, Microsoft.Extensions.DependencyInjection, Version=10.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60],[System.Object, System.Private.CoreLib, Version=10.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].VisitCallSiteMain + 0x3f(Unknown Source)
03-04 18:33:57.996 E/AndroidRuntime(19109): at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitRootCache + 0x3f(Unknown Source)
03-04 18:33:57.996 E/AndroidRuntime(19109): at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor2[[Microsoft.Extensions.DependencyInjection.ServiceLookup.RuntimeResolverContext, Microsoft.Extensions.DependencyInjection, Version=10.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60],[System.Object, System.Private.CoreLib, Version=10.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].VisitCallSite + 0x4f(Unknown Source) 03-04 18:33:57.996 E/AndroidRuntime(19109): at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.Resolve + 0x14(Unknown Source) 03-04 18:33:57.996 E/AndroidRuntime(19109): at Microsoft.Extensions.DependencyInjection.ServiceProvider.CreateServiceAccessor + 0x48(Unknown Source) 03-04 18:33:57.996 E/AndroidRuntime(19109): at System.Collections.Concurrent.ConcurrentDictionary2[[Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceIdentifier, Microsoft.Extensions.DependencyInjection, Version=10.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60],[Microsoft.Extensions.DependencyInjection.ServiceProvider+ServiceAccessor, Microsoft.Extensions.DependencyInjection, Version=10.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60]].GetOrAdd + 0x3f(Unknown Source)
03-04 18:33:57.996 E/AndroidRuntime(19109): at Microsoft.Extensions.DependencyInjection.ServiceProvider.GetService + 0xd(Unknown Source)
03-04 18:33:57.996 E/AndroidRuntime(19109): at Microsoft.Extensions.DependencyInjection.ServiceProvider.GetService + 0x0(Unknown Source)
03-04 18:33:57.996 E/AndroidRuntime(19109): at Microsoft.Maui.MauiContext+WrappedServiceProvider.GetService(//src/Core/src/MauiContext.cs:87)
03-04 18:33:57.996 E/AndroidRuntime(19109): at Microsoft.Maui.MauiContext+WrappedServiceProvider.GetService(//src/Core/src/MauiContext.cs:87)
03-04 18:33:57.996 E/AndroidRuntime(19109): at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService + 0x28(Unknown Source)
03-04 18:33:57.996 E/AndroidRuntime(19109): at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService + 0xb(Unknown Source)
03-04 18:33:57.996 E/AndroidRuntime(19109): at Microsoft.Maui.MauiApplication.OnCreate(/_/src/Core/src/Platform/Android/MauiApplication.cs:46)
03-04 18:33:57.996 E/AndroidRuntime(19109): at Android.App.Application.n_OnCreate + 0xe(Unknown Source)
03-04 18:33:57.996 E/AndroidRuntime(19109): at crc6488302ad6e9e4df1a.MauiApplication.n_onCreate(Native Method)
03-04 18:33:57.996 E/AndroidRuntime(19109): at crc6488302ad6e9e4df1a.MauiApplication.onCreate(MauiApplication.java:27)
03-04 18:33:57.996 E/AndroidRuntime(19109): at android.app.Instrumentation.callApplicationOnCreate(Instrumentation.java:1381)
03-04 18:33:57.996 E/AndroidRuntime(19109): at android.app.ActivityThread.handleBindApplication(ActivityThread.java:7830)
03-04 18:33:57.996 E/AndroidRuntime(19109): at android.app.ActivityThread.-$$Nest$mhandleBindApplication(Unknown Source:0)
03-04 18:33:57.996 E/AndroidRuntime(19109): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2546)
03-04 18:33:57.996 E/AndroidRuntime(19109): at android.os.Handler.dispatchMessage(Handler.java:110)
03-04 18:33:57.996 E/AndroidRuntime(19109): at android.os.Looper.loopOnce(Looper.java:248)
03-04 18:33:57.996 E/AndroidRuntime(19109): at android.os.Looper.loop(Looper.java:338)
03-04 18:33:57.996 E/AndroidRuntime(19109): at android.app.ActivityThread.main(ActivityThread.java:9067)
03-04 18:33:57.996 E/AndroidRuntime(19109): at java.lang.reflect.Method.invoke(Native Method)
03-04 18:33:57.996 E/AndroidRuntime(19109): at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:593)
03-04 18:33:57.996 E/AndroidRuntime(19109): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:932)
An unhandled exception of type 'Android.Runtime.JavaProxyThrowable' occurred in Mono.Android.Runtime.dll

An error occurred in the vsdbg debug session of project 'C:\Projects\TransactionProcessing\TransactionMobile\TransactionProcessor.Mobile\TransactionProcessor.Mobile.csproj': An unhandled exception of type 'Android.Runtime.JavaProxyThrowable' occurred in Mono.Android.Runtime.dll
03-04 18:34:02.633 I/libc (19109): Requested dump for pid 19109 (rocessor.mobile)
The program 'TransactionProcessor.Mobile.dll' has exited with code 0 (0x0).
The vsdbg debug session for project 'C:\Projects\TransactionProcessing\TransactionMobile\TransactionProcessor.Mobile\TransactionProcessor.Mobile.csproj' has been stopped

[StuartFerguson]

@copilot did you see my last comment?

[Copilot]

@copilot did you see my last comment?

Yes, sorry about that — the previous fix was incomplete. The real root cause is that LightTheme.xaml has x:Class (a code-behind), so when MAUI loads it as a merged dictionary, it calls InitializeComponent() which parses LightTheme.xaml in isolation — at that point the parent App.xaml's merged Colors.xaml is not in scope, causing {StaticResource Gray400} to fail.

Fixed in commit fb0532f by adding Colors.xaml to LightTheme.xaml's own MergedDictionaries:

<ResourceDictionary.MergedDictionaries>
    <ResourceDictionary Source="Resources/Styles/Colors.xaml" />
</ResourceDictionary.MergedDictionaries>

This makes LightTheme.xaml self-contained — it can always resolve Gray400 (and any other key from Colors.xaml) regardless of loading order.

[StuartFerguson]

@copilot now get this error
Resource 'Resources/Styles/Resources/Styles/Colors.xaml' not found.

[Copilot]

@copilot now get this error
Resource 'Resources/Styles/Resources/Styles/Colors.xaml' not found.

Fixed in commit abbbf5d. The path in LightTheme.xaml was Resources/Styles/Colors.xaml but since LightTheme.xaml lives inside Resources/Styles/, MAUI was resolving it as Resources/Styles/Resources/Styles/Colors.xaml. Changed it to the sibling-relative path Colors.xaml.