Embarrassing Inheritance Question

Situation:

- I have a third party control that inherits from System.Windows.Controls.ItemsCon开发者_运维技巧trol

- I have an instance of this control called foo

- foo has a ListCollectionView datasource with 5 items and no filter.

- foo.Items.Count gives a result of 0

- (System.Windows.Controls.ItemsControl)(foo)).Items.Count of 5

Where this happens:

- A XAML.cs file's constructor

When this happens:

- In the xaml.cs file's constructor

- After InitializeComponent

Unverified claims:

- The owner of the third party control claims that it does not override Items in any way.

Question:

- Why does foo.Items.Count return a different value than (System.Windows.Controls.ItemsControl)(foo)).Items.Count

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It sounds like they have re-declared the property, i.e.

public new SomeContainer Items { get { ... } }

which is sometimes done to make the type of .Items (etc) more specific; it does, however, break inheritance, unless care is taken to override the underlying implementation. Re their claim - if the above is correct then indeed they aren't overriding it in any way; they are re-declaring it (it depends on how literal you are being with "override", perhaps).

But: you can check this in any reflection tool or IL inspection tool, simply by looking at how the property is declared. Does it have a new or newslot, etc.