Specify a variable implementing 2 interfaces in .net

Question

Is is possible to implement a type specifier with 2 interfaces in .net? Something like:

Public Sub New(obj as ICollection and INotifyCollectionChanged)
    ''Initialize Code
End Sub

John Saunders · Accepted Answer · 2011-03-13 05:46:04Z

6

No, you will have to define an interface that inherits from both of your desired interfaces.

Public Interface IMyCombinedInterface
    Inherits IColllection, INotifyCollectionChanged

End Interface

edited Mar 13, 2011 at 5:46

answered Mar 13, 2011 at 5:18

John Saunders

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1 Comment

PeterM Over a year ago

Thanks Jon. If I implement IMyCombinedInterface, I cant send in a standard ObservableCollection to the constructor because it doesn't implement IMyCombindeInterface. Is a limitation of the language, or am I missing something?

Marc Gravell · Accepted Answer · 2011-03-13 07:50:36Z

4

You can with generic constraints; for example in c#:

public void Something<T>(T obj)
    where T : IFoo, IBar
{....}

Then Something(value) will work only when value is typed as something that implements both IFoo and IBar.

answered Mar 13, 2011 at 7:50

Marc Gravell

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2 Comments

PeterM Over a year ago

Thanks Mark, this is exactly what I need. In Vb.net you can add the multiple constraints inside curly braces. See geekswithblogs.net/TechnicalDebtor/archive/2008/11/18/…

Ross Presser Over a year ago

Apparently only when defining a Generic type. Not when trying to pass to a function. I.e. you can't do this: Public Function Foo(x as {iBar, iBaz}) As Boolean

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