Fix MVVM Toolkit LINQ expression issues on .NET Framework

Microsoft.Toolkit.Mvvm/ComponentModel/ObservableValidator.cs

@@ -488,6 +488,21 @@ static Action<object> GetValidationAction(Type type)
             // Fallback method to create the delegate with a compiled LINQ expression
             static Action<object> GetValidationActionFallback(Type type)
             {
+                // Get the collection of all properties to validate
+                (string Name, MethodInfo GetMethod)[] validatableProperties = (
+                    from property in type.GetProperties(BindingFlags.Instance | BindingFlags.Public)
+                    where property.GetIndexParameters().Length == 0 &&
+                          property.GetCustomAttributes<ValidationAttribute>(true).Any()
+                    let getMethod = property.GetMethod
+                    where getMethod is not null
+                    select (property.Name, getMethod)).ToArray();
+
+                // Short path if there are no properties to validate
+                if (validatableProperties.Length == 0)
+                {
+                    return static _ => { };
+                }
+
                 // MyViewModel inst0 = (MyViewModel)arg0;
                 ParameterExpression arg0 = Expression.Parameter(typeof(object));
                 UnaryExpression inst0 = Expression.Convert(arg0, type);
@@ -513,14 +528,10 @@ static Action<object> GetValidationActionFallback(Type type)
                 // ObservableValidator externally, but that is fine because IL doesn't really have
                 // a concept of member visibility, that's purely a C# build-time feature.
                 BlockExpression body = Expression.Block(
-                    from property in type.GetProperties(BindingFlags.Instance | BindingFlags.Public)
-                    where property.GetIndexParameters().Length == 0 &&
-                          property.GetCustomAttributes<ValidationAttribute>(true).Any()
-                    let getter = property.GetMethod
-                    where getter is not null
+                    from property in validatableProperties
                     select Expression.Call(inst0, validateMethod, new Expression[]
                     {
-                        Expression.Convert(Expression.Call(inst0, getter), typeof(object)),
+                        Expression.Convert(Expression.Call(inst0, property.GetMethod), typeof(object)),
                         Expression.Constant(property.Name)
                     }));
 

Microsoft.Toolkit.Mvvm/Messaging/IMessengerExtensions.cs

@@ -153,6 +153,20 @@ static Action<IMessenger, object, TToken> LoadRegistrationMethodsForType(Type re
             // The LINQ codegen bloat is not really important for the same reason.
             static Action<IMessenger, object, TToken> LoadRegistrationMethodsForTypeFallback(Type recipientType)
             {
+                // Get the collection of validation methods
+                MethodInfo[] registrationMethods = (
+                    from interfaceType in recipientType.GetInterfaces()
+                    where interfaceType.IsGenericType &&
+                          interfaceType.GetGenericTypeDefinition() == typeof(IRecipient<>)
+                    let messageType = interfaceType.GenericTypeArguments[0]
+                    select MethodInfos.RegisterIRecipient.MakeGenericMethod(messageType, typeof(TToken))).ToArray();
+
+                // Short path if there are no message handlers to register
+                if (registrationMethods.Length == 0)
+                {
+                    return static (_, _, _) => { };
+                }
+
                 // Input parameters (IMessenger instance, non-generic recipient, token)
                 ParameterExpression
                     arg0 = Expression.Parameter(typeof(IMessenger)),
@@ -178,11 +192,7 @@ static Action<IMessenger, object, TToken> LoadRegistrationMethodsForTypeFallback
                 // We also add an explicit object conversion to cast the input recipient type to
                 // the actual specific type, so that the exposed message handlers are accessible.
                 BlockExpression body = Expression.Block(
-                    from interfaceType in recipientType.GetInterfaces()
-                    where interfaceType.IsGenericType &&
-                          interfaceType.GetGenericTypeDefinition() == typeof(IRecipient<>)
-                    let messageType = interfaceType.GenericTypeArguments[0]
-                    let registrationMethod = MethodInfos.RegisterIRecipient.MakeGenericMethod(messageType, typeof(TToken))
+                    from registrationMethod in registrationMethods
                     select Expression.Call(registrationMethod, new Expression[]
                     {
                         arg0,

UnitTests/UnitTests.NetCore/Mvvm/Test_ObservablePropertyAttribute.cs

@@ -12,7 +12,7 @@
 using Microsoft.Toolkit.Mvvm.ComponentModel;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 
-#pragma warning disable SA1124
+#pragma warning disable SA1124, SA1307, SA1401
 
 #nullable enable
 
@@ -371,7 +371,7 @@ public partial class ModelWithValuePropertyWithValidation : ObservableValidator
             [MinLength(5)]
             private string? value;
         }
-  
+
         public partial class ViewModelWithValidatableGeneratedProperties : ObservableValidator
         {
             [Required]

UnitTests/UnitTests.Shared/Mvvm/Test_ObservableValidator.cs

@@ -7,6 +7,7 @@
 using System.ComponentModel;
 using System.ComponentModel.DataAnnotations;
 using System.Linq;
+using System.Reflection;
 using System.Text.RegularExpressions;
 using Microsoft.Toolkit.Mvvm.ComponentModel;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
@@ -335,6 +336,54 @@ public void Test_ObservableValidator_ValidateAllProperties()
             model.Age = -10;
 
             model.ValidateAllProperties();
+
+            Assert.IsTrue(model.HasErrors);
+            Assert.IsTrue(events.Count == 1);
+            Assert.IsTrue(events.Any(e => e.PropertyName == nameof(Person.Age)));
+        }
+
+        [TestCategory("Mvvm")]
+        [TestMethod]
+        public void Test_ObservableValidator_ValidateAllProperties_WithFallback()
+        {
+            var model = new PersonWithDeferredValidation();
+            var events = new List<DataErrorsChangedEventArgs>();
+
+            MethodInfo[] staticMethods = typeof(ObservableValidator).GetMethods(BindingFlags.Static | BindingFlags.NonPublic);
+            MethodInfo validationMethod = staticMethods.Single(static m => m.Name.Contains("GetValidationActionFallback"));
+            Func<Type, Action<object>> validationFunc = (Func<Type, Action<object>>)validationMethod.CreateDelegate(typeof(Func<Type, Action<object>>));
+            Action<object> validationAction = validationFunc(model.GetType());
+
+            model.ErrorsChanged += (s, e) => events.Add(e);
+
+            validationAction(model);
+
+            Assert.IsTrue(model.HasErrors);
+            Assert.IsTrue(events.Count == 2);
+
+            // Note: we can't use an index here because the order used to return properties
+            // from reflection APIs is an implementation detail and might change at any time.
+            Assert.IsTrue(events.Any(e => e.PropertyName == nameof(Person.Name)));
+            Assert.IsTrue(events.Any(e => e.PropertyName == nameof(Person.Age)));
+
+            events.Clear();
+
+            model.Name = "James";
+            model.Age = 42;
+
+            validationAction(model);
+
+            Assert.IsFalse(model.HasErrors);
+            Assert.IsTrue(events.Count == 2);
+            Assert.IsTrue(events.Any(e => e.PropertyName == nameof(Person.Name)));
+            Assert.IsTrue(events.Any(e => e.PropertyName == nameof(Person.Age)));
+
+            events.Clear();
+
+            model.Age = -10;
+
+            validationAction(model);
+
             Assert.IsTrue(model.HasErrors);
             Assert.IsTrue(events.Count == 1);
             Assert.IsTrue(events.Any(e => e.PropertyName == nameof(Person.Age)));
@@ -414,6 +463,34 @@ public void Test_ObservableValidator_ValidationWithFormattedDisplayName()
             Assert.AreEqual(allErrors[1].ErrorMessage, $"SECOND: {nameof(ValidationWithDisplayName.AnotherRequiredField)}.");
         }
 
+        // See: https://github.com/CommunityToolkit/WindowsCommunityToolkit/issues/4272
+        [TestCategory("Mvvm")]
+        [TestMethod]
+        [DataRow(typeof(MyBase))]
+        [DataRow(typeof(MyDerived2))]
+        public void Test_ObservableRecipient_ValidationOnNonValidatableProperties(Type type)
+        {
+            MyBase viewmodel = (MyBase)Activator.CreateInstance(type);
+
+            viewmodel.ValidateAll();
+        }
+
+        // See: https://github.com/CommunityToolkit/WindowsCommunityToolkit/issues/4272
+        [TestCategory("Mvvm")]
+        [TestMethod]
+        [DataRow(typeof(MyBase))]
+        [DataRow(typeof(MyDerived2))]
+        public void Test_ObservableRecipient_ValidationOnNonValidatableProperties_WithFallback(Type type)
+        {
+            MyBase viewmodel = (MyBase)Activator.CreateInstance(type);
+
+            MethodInfo[] staticMethods = typeof(ObservableValidator).GetMethods(BindingFlags.Static | BindingFlags.NonPublic);
+            MethodInfo validationMethod = staticMethods.Single(static m => m.Name.Contains("GetValidationActionFallback"));
+            Func<Type, Action<object>> validationFunc = (Func<Type, Action<object>>)validationMethod.CreateDelegate(typeof(Func<Type, Action<object>>));
+
+            validationFunc(viewmodel.GetType())(viewmodel);
+        }
+
         public class Person : ObservableValidator
         {
             private string name;
@@ -631,5 +708,22 @@ public string AnotherRequiredField
                 set => SetProperty(ref this.anotherRequiredField, value, true);
             }
         }
+
+        public class MyBase : ObservableValidator
+        {
+            public int? MyDummyInt { get; set; } = 0;
+
+            public void ValidateAll()
+            {
+                ValidateAllProperties();
+            }
+        }
+
+        public class MyDerived2 : MyBase
+        {
+            public string Name { get; set; }
+
+            public int SomeRandomproperty { get; set; }
+        }
     }
 }