Simple question about set...

Question

Does it only trigger when there is an assignment to the property or does it trigger with any change further on down the line? Like, if I have a property named MyProp in MyClass of type TestClass (assume testclass has a TestField field), will MyProp trigger the set code with a line like "MyProp.TestField = "cows are pretty"" or would it only trigger on something like "MyProp = MyOtherTestClass"

Danny · Answer

I believe my example was a bit flawed. I don't think the provided solutions really would work with my problem. Let me explain a bit about what I'm working on: This project is an employee scheduling program for a class I'm in. I have an employee class which contains an employee's general information as well as two properties pointing to different classes (their availibility and working schedules). My schedule classes are set up in that there is a base schedule class which contains methods to create an internal calendar. The working and availibility schedule classes inherit the base class so they can build calendars and assign to them separately. Within those schedule class's calendars there are numerous instances of custom month week and day classes that I have made. I need an IsModified flag to get thrown any time ANY of that is changed for an employee. Like if I were to do something like: EmployeeCollection[4].Availibility.Months[1].Weeks[12].TimeBlocks[0].IsAvailible = true; ...I need it to walk up from a very specific change several layers down of the availibility property to the main instance of an employee class. I can't seem to find a way to do it that isn't stupidly redundant and if I know anything about programming it's that if something seems redundant it's being done wrong.

Brandon Lewis · Answer

You could create an event that is triggered whenever that property is set and maybe build some custom event arguments to pass whenever the event is raised. Then raise the event in the set accessor of the MyProp and it will notify any subscribers of the change in MyProp. Something like: public event EventHandler MyPropChanged; private TestClass myProp; public TestClass MyProp { set { //Set the value myProp = value ; //If the changed event has subscribers //then raise it. if (MyPropChanged != null ) { MyPropChanged( this  new EventArgs ()); } } } You could also create a set of event arguments and pass them as the type parameter of the generic EventHandler class.

Danny · Answer

Hmm if I understand you correctly this is bad news for my current project. I need some way to have the first class's property (TestProp in my example) react to any changes of its backing field. More specifically I am working with a generic employee class. The employee class has a property to represent their working schedule. Whenever there are any changes to the schedule I need it to set a modified switch in the main employee class. What's the best way to go about this?

Alan · Answer

In this line: MyProp.TestField = cows are pretty; the MyClass.MyProp 'get' is first called which returns a TestClass object. The TestField property of that object is then 'set' to the string: cows are pretty. In this line: MyProp = MyOtherTestClass; the MyClass.MyProp 'set' is called and the backing field is set to the object MyOtherTestClass.