TL;DR; Explains issues using ObservableCollection with generic types in .NET, why errors occur, and discusses workarounds and limitations when working with custom classes.
I seam to be having a little problem. Now, this may be me being stupid, but I can’t get an ObservableCollection to work if you pass it a generic type!
For example, consider the following code:
1Public Class ItemBitCollection(Of TItem) 2 Inherits ObservableCollection(Of ItemBit(Of TItem)) 3 4 5End Class 6 7Public Class ItemBit(Of TItem) 8 9 Private m_item As TItem 10 11End Class
Now, if you create an instance of ItemBitCollection you will see an error on the IDE regardless of wither you use a custom object type or a String type to initialise it:
Why does this not work? What is ObservableCollection doing that maybe it should not? Time to get Reflector out…
After some looking at the source I am still none the wiser. Even if you dumb down your classes to the bare minimum you cant pass a generic type into an ObservableCollection.
This is a limitation if you ask me…
Annoying solution:
If you create a fixed class type:
1Public Class ItemBitCollection(Of TItemBit) 2 Inherits ObservableCollection(Of TItemBit) 3 4End Class 5 6Public MustInherit Class ItemBit(Of TItem) 7 8 Private m_item As TItem 9 10End Class 11 12Public Class DefaultItemBit 13 Inherits ItemBit(Of String) 14 15End Class
And then pass that class in it does work:
1Dim o As New ItemBitCollection(Of DefaultItemBit)
Although this is a work around, it causes other problems in my code… Ahh well… worth a try…
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