Add Error event in Blazor ViewModel (#3279) (#3915)

* Add Error event in Blazor ViewModel (#3279)

* fix tests

* Error event provides Exception

Source/Csla.Blazor.Test/Fakes/FakePerson.cs

@@ -12,6 +12,8 @@ public class FakePerson : BusinessBase<FakePerson>
  public static Csla.PropertyInfo<string> MobileTelephoneProperty = RegisterProperty<string>(nameof(MobileTelephone));
  public static Csla.PropertyInfo<FakePersonEmailAddresses> EmailAddressesProperty = RegisterProperty<FakePersonEmailAddresses>(nameof(EmailAddresses));
 
+ public static string FirstNameFailOnInsertValue = "FailOnInsert";
+
  #region Properties 
 
  [MaxLength(25)]
@@ -92,6 +94,13 @@ private void Create([Inject] IChildDataPortal<FakePersonEmailAddresses> dataPort
  BusinessRules.CheckRules();
  }
 
+ [Insert]
+ private void Insert()
+ {
+ if (FirstName == FirstNameFailOnInsertValue) {
+ throw new Exception("Insert failed");
+ }
+ }
  #endregion
 
  }

Source/Csla.Blazor.Test/ViewModelSaveAsyncErrorTests.cs

@@ -0,0 +1,97 @@
+using Csla.Blazor.Test.Fakes;
+using Csla.TestHelpers;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+namespace Csla.Blazor.Test
+{
+ [TestClass]
+ public class ViewModelSaveAsyncErrorTests
+ {
+ private static TestDIContext _testDIContext;
+
+ [ClassInitialize]
+ public static void ClassInitialize(TestContext context)
+ {
+ _testDIContext = TestDIContextFactory.CreateDefaultContext();
+ }
+
+ [TestMethod]
+ public async Task SavingFailure_ErrorEventIsInvoked()
+ {
+ // Arrange
+ var person = GetValidFakePerson();
+ var appCntxt = _testDIContext.CreateTestApplicationContext();
+ var vm = new ViewModel<FakePerson>(appCntxt)
+ {
+ Model = person,
+ };
+ var error = 0;
+ vm.Error += (o, e) =>
+ {
+ error++;
+ Assert.IsNotNull(e.Error);
+ // these fields should be populated when Error event is triggered
+ Assert.IsNotNull(vm.Exception);
+ Assert.IsNotNull(vm.ViewModelErrorText);
+ Assert.AreSame(e.Error, vm.Exception);
+ Assert.AreSame(o, vm);
+ };
+ person.FirstName = FakePerson.FirstNameFailOnInsertValue;
+
+ // Act
+ await vm.SaveAsync();
+
+ // Assert
+ Assert.AreEqual(1, error); // Error event should have been triggered only once
+ Assert.IsNotNull(vm.Exception);
+ Assert.IsNotNull(vm.ViewModelErrorText);
+ }
+
+ [TestMethod]
+ public async Task SavingSuccess_ErrorEventIsNotInvoked()
+ {
+ // Arrange
+ var person = GetValidFakePerson();
+ var appCntxt = _testDIContext.CreateTestApplicationContext();
+ var vm = new ViewModel<FakePerson>(appCntxt)
+ {
+ Model = person,
+ };
+ var error = false;
+ vm.Error += (o, e) =>
+ {
+ error = true;
+ };
+
+ // Act
+ await vm.SaveAsync();
+
+ // Assert
+ Assert.IsFalse(error); // Error event shouldn't have been triggered
+ Assert.IsNull(vm.Exception);
+ Assert.IsNull(vm.ViewModelErrorText);
+ }
+
+ #region Helper Methods
+
+ FakePerson GetValidFakePerson()
+ {
+ IDataPortal<FakePerson> dataPortal;
+ FakePerson person;
+
+ // Create an instance of a DataPortal that can be used for instantiating objects
+ dataPortal = _testDIContext.CreateDataPortal<FakePerson>();
+ person = dataPortal.Create();
+
+ person.FirstName = "John";
+ person.LastName = "Smith";
+ person.HomeTelephone = "01234 567890";
+
+ return person;
+ }
+
+ #endregion
+
+ }
+
+}

Source/Csla.Blazor/ViewModel.cs

@@ -40,6 +40,10 @@ public ViewModel(ApplicationContext applicationContext)
  /// </summary>
  public event Action Saved;
  /// <summary>
+ /// Event raised when failed to save Model.
+ /// </summary>
+ public event EventHandler<Core.ErrorEventArgs> Error;
+ /// <summary>
  /// Event raised when Model is changing.
  /// </summary>
  public event Action<T, T> ModelChanging;
@@ -284,6 +288,9 @@ public async Task SaveAsync()
  {
  HookChangedEvents(Model);
  IsBusy = false;
+ if (Exception != null) {
+ Error?.Invoke(this, new Core.ErrorEventArgs(this, Exception)); 
+ }
  }
  }