Scan only declared methods for JS interop (#1320)

* Scan only declared methods for JS interop

* Add DotNetDispatcher test for JS invokable method on base class

src/Microsoft.JSInterop/DotNetDispatcher.cs

@@ -240,7 +240,11 @@ namespace Microsoft.JSInterop
             var result = new Dictionary<string, (MethodInfo, Type[])>();
             var invokableMethods = GetRequiredLoadedAssembly(assemblyName)
                 .GetExportedTypes()
-                .SelectMany(type => type.GetMethods())
+                .SelectMany(type => type.GetMethods(
+                    BindingFlags.Public | 
+                    BindingFlags.DeclaredOnly | 
+                    BindingFlags.Instance |
+                    BindingFlags.Static))
                 .Where(method => method.IsDefined(typeof(JSInvokableAttribute), inherit: false));
             foreach (var method in invokableMethods)
             {

test/Microsoft.JSInterop.Test/DotNetDispatcherTest.cs

@@ -155,6 +155,21 @@ namespace Microsoft.JSInterop.Test
             Assert.True(targetInstance.DidInvokeMyInvocableInstanceVoid);
         });
 
+        [Fact]
+        public Task CanInvokeBaseInstanceVoidMethod() => WithJSRuntime(jsRuntime =>
+        {
+            // Arrange: Track some instance
+            var targetInstance = new DerivedClass();
+            jsRuntime.Invoke<object>("unimportant", new DotNetObjectRef(targetInstance));
+
+            // Act
+            var resultJson = DotNetDispatcher.Invoke(null, "BaseClassInvokableInstanceVoid", 1, null);
+
+            // Assert
+            Assert.Null(resultJson);
+            Assert.True(targetInstance.DidInvokeMyBaseClassInvocableInstanceVoid);
+        });
+
         [Fact]
         public Task CannotUseDotNetObjectRefAfterDisposal() => WithJSRuntime(jsRuntime =>
         {
@@ -376,6 +391,21 @@ namespace Microsoft.JSInterop.Test
             }
         }
 
+        public class BaseClass
+        {
+            public bool DidInvokeMyBaseClassInvocableInstanceVoid;
+
+            [JSInvokable]
+            public void BaseClassInvokableInstanceVoid()
+            {
+                DidInvokeMyBaseClassInvocableInstanceVoid = true;
+            }
+        }
+
+        public class DerivedClass : BaseClass
+        {
+        }
+
         public class TestDTO
         {
             public string StringVal { get; set; }