Fix RelayCommand binding inference for On*Async patterns

src/Controls/src/BindingSourceGen/ITypeSymbolExtensions.cs

@@ -68,31 +68,59 @@ public static bool TryGetRelayCommandPropertyType(this ITypeSymbol symbol, strin
 		// Extract the method name (property name without "Command" suffix)
 		var methodName = propertyName.Substring(0, propertyName.Length - "Command".Length);
 
-		// Look for a method with the base name - search in the type and base types
-		var methods = GetAllMethods(symbol, methodName);
-
-		foreach (var method in methods)
+		// CommunityToolkit.Mvvm command naming supports these patterns:
+		// - Save => SaveCommand
+		// - SaveAsync => SaveCommand
+		// - OnSave => SaveCommand
+		// - OnSaveAsync => SaveCommand
+		foreach (var candidateMethodName in GetRelayCommandMethodNameCandidates(methodName))
 		{
-			// Check if the method has the RelayCommand attribute
-			var hasRelayCommand = method.GetAttributes().Any(attr =>
-				attr.AttributeClass?.Name == "RelayCommandAttribute" ||
-				attr.AttributeClass?.ToDisplayString() == "CommunityToolkit.Mvvm.Input.RelayCommandAttribute");
-
-			if (hasRelayCommand)
+			var methods = GetAllMethods(symbol, candidateMethodName);
+			foreach (var method in methods)
 			{
-				// Try to find the ICommand interface type
-				var icommandType = compilation.GetTypeByMetadataName("System.Windows.Input.ICommand");
-				if (icommandType != null)
+				// Check if the method has the RelayCommand attribute
+				var hasRelayCommand = method.GetAttributes().Any(attr =>
+					attr.AttributeClass?.Name == "RelayCommandAttribute" ||
+					attr.AttributeClass?.ToDisplayString() == "CommunityToolkit.Mvvm.Input.RelayCommandAttribute");
+
+				if (hasRelayCommand)
 				{
-					commandType = icommandType;
-					return true;
+					// Try to find the ICommand interface type
+					var icommandType = compilation.GetTypeByMetadataName("System.Windows.Input.ICommand");
+					if (icommandType != null)
+					{
+						commandType = icommandType;
+						return true;
+					}
 				}
 			}
 		}
 
 		return false;
 	}
 
+	private static System.Collections.Generic.IEnumerable<string> GetRelayCommandMethodNameCandidates(string methodName)
+	{
+		// CommunityToolkit strips "On" prefix: OnSave() → SaveCommand, not OnSaveCommand.
+		// So if methodName starts with "On", the base name would only match methods that generate
+		// a *different* command property (e.g., "OnLoad" method → "LoadCommand", not "OnLoadCommand").
+		// We skip these candidates to avoid false-positive diagnostic suppression.
+		if (!methodName.StartsWith("On", System.StringComparison.Ordinal))
+		{
+			yield return methodName;
+			yield return methodName + "Async";
+		}
+
+		if (methodName.Length > 0
+			&& char.IsUpper(methodName[0])
+			&& !methodName.StartsWith("On", System.StringComparison.Ordinal))
+		{
+			var onMethodName = "On" + methodName;
+			yield return onMethodName;
+			yield return onMethodName + "Async";
+		}
+	}
+
 	/// <summary>
 	/// Checks if a property name could be generated by CommunityToolkit.Mvvm's [ObservableProperty] attribute,
 	/// and returns the inferred property type if found.

src/Controls/tests/BindingSourceGen.UnitTests/RelayCommandTests.cs

@@ -126,6 +126,58 @@ private void Save()
 		Assert.Equal("System.Windows.Input.ICommand", commandType!.ToDisplayString());
 	}
 
+	[Fact]
+	public void DetectsRelayCommandMethodWithOnPrefixAndAsyncSuffix()
+	{
+		var source = @"
+			using Microsoft.CodeAnalysis;
+			using Microsoft.CodeAnalysis.CSharp;
+			using System.Linq;
+			using System.Threading.Tasks;
+
+			namespace System.Windows.Input
+			{
+				public interface ICommand
+				{
+					event System.EventHandler CanExecuteChanged;
+					bool CanExecute(object parameter);
+					void Execute(object parameter);
+				}
+			}
+
+			namespace CommunityToolkit.Mvvm.Input
+			{
+				[System.AttributeUsage(System.AttributeTargets.Method)]
+				public class RelayCommandAttribute : System.Attribute { }
+			}
+
+			namespace TestApp
+			{
+				public class MyViewModel
+				{
+					[CommunityToolkit.Mvvm.Input.RelayCommand]
+					private Task OnSaveAsync()
+					{
+						return Task.CompletedTask;
+					}
+				}
+			}
+			";
+
+		var compilation = Microsoft.CodeAnalysis.CSharp.CSharpCompilation.Create("test")
+			.AddSyntaxTrees(CSharpSyntaxTree.ParseText(source))
+			.AddReferences(MetadataReference.CreateFromFile(typeof(object).Assembly.Location));
+
+		var myViewModelType = compilation.GetTypeByMetadataName("TestApp.MyViewModel");
+		Assert.NotNull(myViewModelType);
+
+		var canInfer = myViewModelType.TryGetRelayCommandPropertyType("SaveCommand", compilation, out var commandType);
+
+		Assert.True(canInfer, "Should infer SaveCommand from OnSaveAsync method with [RelayCommand].");
+		Assert.NotNull(commandType);
+		Assert.Equal("System.Windows.Input.ICommand", commandType!.ToDisplayString());
+	}
+
 	[Fact]
 	public void DoesNotDetectCommandPropertyWithoutAttribute()
 	{

src/Controls/tests/SourceGen.UnitTests/BindingDiagnosticsTests.cs

@@ -54,6 +54,48 @@ public class ViewModel
 		Assert.Contains("ViewModel", message, System.StringComparison.Ordinal);
 	}
 
+	[Fact]
+	public void BindingToRelayCommandGeneratedFromOnAsyncMethod_DoesNotReportPropertyNotFound()
+	{
+		var 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:test="clr-namespace:Test"
+	x:Class="Test.TestPage"
+	x:DataType="test:ViewModel">
+	<Button Command="{Binding SaveCommand}" />
+</ContentPage>
+""";
+
+		var csharp = @"
+namespace CommunityToolkit.Mvvm.Input
+{
+	[System.AttributeUsage(System.AttributeTargets.Method)]
+	public class RelayCommandAttribute : System.Attribute { }
+}
+
+namespace Test
+{
+	public partial class TestPage : Microsoft.Maui.Controls.ContentPage { }
+
+	public class ViewModel
+	{
+		[CommunityToolkit.Mvvm.Input.RelayCommand]
+		private System.Threading.Tasks.Task OnSaveAsync() => System.Threading.Tasks.Task.CompletedTask;
+	}
+}
+";
+
+		var compilation = CreateMauiCompilation()
+			.AddSyntaxTrees(Microsoft.CodeAnalysis.CSharp.CSharpSyntaxTree.ParseText(csharp));
+		var result = RunGenerator<XamlGenerator>(compilation, new AdditionalXamlFile("Test.xaml", xaml), assertNoCompilationErrors: false);
+
+		Assert.DoesNotContain(result.Diagnostics, d => d.Id == "MAUIG2045");
+	}
+
 	[Fact]
 	public void BindingIndexerNotClosed_ReportsCorrectDiagnostic()
 	{