Make ComponentFactory throw if you try to use [Inject] with a property that has no setter (otherwise it could be confusing)

src/Microsoft.AspNetCore.Blazor/Components/ComponentFactory.cs

@@ -52,16 +52,25 @@ namespace Microsoft.AspNetCore.Blazor.Components
             // Do all the reflection up front
             var injectableProperties = type.GetTypeInfo()
                 .GetProperties(_injectablePropertyBindingFlags)
-                .Where(p => p.GetCustomAttribute<InjectAttribute>() != null)
+                .Where(p => p.GetCustomAttribute<InjectAttribute>() != null);
-                .Where(p => p.SetMethod != null);
             var injectables = injectableProperties.Select(property =>
-            (
+            {
-                propertyName: property.Name,
+                if (property.SetMethod == null)
-                propertyType: property.PropertyType,
+                {
-                setter: (IPropertySetter)Activator.CreateInstance(
+                    throw new InvalidOperationException($"Cannot provide a value for property " +
-                    typeof(PropertySetter<,>).MakeGenericType(type, property.PropertyType),
+                        $"'{property.Name}' on type '{type.FullName}' because the property " +
-                    property.SetMethod)
+                        $"has no setter.");
-            )).ToArray();
+                }
+
+                return
+                (
+                    propertyName: property.Name,
+                    propertyType: property.PropertyType,
+                    setter: (IPropertySetter)Activator.CreateInstance(
+                        typeof(PropertySetter<,>).MakeGenericType(type, property.PropertyType),
+                        property.SetMethod)
+                );
+            }).ToArray();
 
             // Return an action whose closure can write all the injected properties
             // without any further reflection calls (just typecasts)
@@ -72,7 +81,7 @@ namespace Microsoft.AspNetCore.Blazor.Components
                     var serviceInstance = _serviceProvider.GetService(injectable.propertyType);
                     if (serviceInstance == null)
                     {
-                        throw new InvalidOperationException($"Cannot provide value for property " +
+                        throw new InvalidOperationException($"Cannot provide a value for property " +
                             $"'{injectable.propertyName}' on type '{type.FullName}'. There is no " +
                             $"registered service of type '{injectable.propertyType}'.");
                     }

test/Microsoft.AspNetCore.Blazor.Test/DependencyInjectionTest.cs

@@ -42,13 +42,16 @@ namespace Microsoft.AspNetCore.Blazor.Test
         }
 
         [Fact]
-        public void IgnoresGetOnlyProperties()
+        public void ThrowsForInjectablePropertiesWithoutSetter()
         {
-            // Arrange/Act
+            var ex = Assert.Throws<InvalidOperationException>(() =>
-            var component = InstantiateComponent<HasGetOnlyProperty>();
+            {
+                InstantiateComponent<HasGetOnlyPropertyWithInject>();
+            });
 
-            // Assert
+            Assert.Equal($"Cannot provide a value for property '{nameof(HasInjectableProperty.MyService)}' " +
-            Assert.Null(component.MyService);
+                $"on type '{typeof(HasGetOnlyPropertyWithInject).FullName}' because the property " +
+                $"has no setter.", ex.Message);
         }
 
         [Fact]
@@ -59,7 +62,7 @@ namespace Microsoft.AspNetCore.Blazor.Test
                 InstantiateComponent<HasInjectableProperty>();
             });
 
-            Assert.Equal($"Cannot provide value for property '{nameof(HasInjectableProperty.MyService)}' " +
+            Assert.Equal($"Cannot provide a value for property '{nameof(HasInjectableProperty.MyService)}' " +
                 $"on type '{typeof(HasInjectableProperty).FullName}'. There is no registered service " +
                 $"of type '{typeof(IMyService).FullName}'.", ex.Message);
         }
@@ -130,7 +133,7 @@ namespace Microsoft.AspNetCore.Blazor.Test
             public static IMyService StaticPropertyWithoutInject { get; set; }
         }
 
-        class HasGetOnlyProperty : TestComponent
+        class HasGetOnlyPropertyWithInject : TestComponent
         {
             [Inject] public IMyService MyService { get; }
         }