Moq raise event error - Parameter count mismatch
c#, events, mocking, moq, vsto
Solution
There are two overloads of `Mock.Raise` - you will either need to pass an `EventArgs`, or a `params object[]` as the second `args` parameter. In your case, you can use the latter and pass the `string name` of the property changed:
e.g.
mailItemStub.Raise(x => x.PropertyChange += (name) => { }, "FooBar");
More here
Problem
Background I have the following scenario: - MailItemProxy class with a constructor with a single argument of type MailItem (MailItem is actually part of the Microsoft.Office.Interop.Outlook namespace) - Within the constructor of MailItemProxy, an event called PropertyChange (from the Outlook MailItem class) is registered: ``` public MailItemProxy(MailItem mailItem) { this.mailItem = mailItem; this.mailItem.PropertyChange += this.MailItem_PropertyChange; } ``` My MailItemProxy class implements INotifyPropertyChanged so has its own PropertyChanged event (notice this is "PropertyChanged" rather than the Outlook MailItem's own "PropertyChange" tense). The *MailItem_PropertyChange* event handler is as follows: ``` private void MailItem_PropertyChange(string name) { if (this.PropertyChanged != null) { this.PropertyChanged(this, new PropertyChangedEventArgs(name)); } } ``` Intention My intention here is to test when the MailItem PropertyChange event is fired, the class under test (MailItemProxy) has subscribed to that event correctly. The test framework I am using is Moq. The issue I am getting is I receive a runtime error "Parameter count mismatch" on my Act line where I attempt to raise a PropertyChange event for the mailItemStub. The PropertyChange event does just take in one parameter of type string as defined by delegate ItemEvents_10_PropertyChangeEventHandler(string Name) within the Microsoft.Office.Interop.Outlook namespace. If I remove the last two Arrange lines for mailItemProxy, the Act line then runs fine for some reason but I obviously need the proxy as this is the class I am testing. Any ideas why I am receiving this error? ``` [TestMethod] public void PropertyChanged_WhenMailItemPropertyChange_EventIsCalled() { // Arrange bool eventDispatched = false; var mailItemStub = new Mock<MailItem>(); var mailItemProxy = new MailItemProxy(mailItemStub.Object); mailItemProxy.PropertyChanged += (sender, args) => { eventDispatched = true; }; // Act mailItemStub.Raise(x => x.PropertyChange += (name) => { }); // Assert Assert.IsTrue(eventDispatched); } ``` Stack Trace ``` Test Name: PropertyChanged_WhenMailItemPropertyChange_EventIsCalled Test Outcome: Failed Test Duration: 0:00:00.2764026 Result Message: Test method UI.Office.UnitTests.MailItemProxyTest.PropertyChanged_WhenMailItemPropertyChange_EventIsCalled threw exception: System.Reflection.TargetParameterCountException: Parameter count mismatch. Result StackTrace: at Moq.Mock`1.Raise(Action`1 eventExpression, Object[] args) at UI.Office.UnitTests.MailItemProxyTest.PropertyChanged_WhenMailItemPropertyChange_EventIsCalled() ```