Question

I am instantiating my objects with the classical

object myObject = Activator.CreateInstance(myType);

code and if works fine.
The thing is that, now, Id like to instantiate an object and in its constructor, there is a reference to another object.
So if I just do the code above, I got a NullReferenceException exception :

Object reference not set to an instance of an object.

I tried to instantiate the concerned object (with Activator.CreateInstance) but I got the same exception…
I feel like instantiating the problematic object before my 2nd CreateInstance call is not enough. What should I do ?

EDIT : here’s the code of the problem

//A regionManager in needed by MainView as far as I understand the Exception's details
var regionManager = Assembly.LoadFrom("RegionView.dll");
Type rmType = regionManager.GetType("Framework.Hmi.RegionManager");
object obj = Activator.CreateInstance(rmType);
//This works !

var shellViewLibrary = Assembly.LoadFrom("ShellView.dll");
Type svType = shellViewLibrary.GetType("Framework.ShellView.MainView");
object objjj = Activator.CreateInstance(svType);

The last line fails and the error is a NullReferenceException with the details :

at Hmi.RegionManager.get_RegionFactory()
at Hmi.RegionManager.CreateRegion(DependencyObject element)
at Hmi.RegionManager.OnSetRegionNameCallback(DependencyObject element, DependencyPropertyChangedEventArgs args)
at System.Windows.DependencyObject.OnPropertyChanged(DependencyPropertyChangedEventArgs e)
at System.Windows.FrameworkElement.OnPropertyChanged(DependencyPropertyChangedEventArgs e)
at System.Windows.DependencyObject.NotifyPropertyChange(DependencyPropertyChangedEventArgs args)
at System.Windows.DependencyObject.UpdateEffectiveValue(EntryIndex entryIndex, DependencyProperty dp, PropertyMetadata metadata, EffectiveValueEntry oldEntry, EffectiveValueEntry& newEntry, Boolean coerceWithDeferredReference, Boolean coerceWithCurrentValue, OperationType operationType)
[...]

I call c/c the 30/40 other error lines but I don’t think it is that usefull…

Answer 1

When you say your constructor references another object, do you mean you should be passing it to the constructor as a parameter? If so, then there is an overload for Activator.CreateInstance that allows you to specify the parameter values. See MSDN for details, but basically, you add them after the type.