Why do arrays in .net only implement IEnumerable and not IEnumerable<T>?

c# .net arrays ienumerable ienumerator
devoured elysium picture devoured elysium · May 5, 2010 · Viewed 30.9k times · Source

I was implementing my own ArrayList class and was left surprised when I realised that

public System.Collections.Generic.IEnumerator<T> GetEnumerator() {
    return _array.GetEnumerator();
}

didn't work. What is the reason arrays don't implement IEnumerator in .NET?

Is there any work-around?

Thanks

Answer

Richard picture Richard · May 5, 2010

Arrays do implement IEnumerable<T>, but it is done as part of the special knowledge the CLI has for arrays. This works as if it were an explicit implementation (but isn't: it is done at runtime). Many tools will not show this implementation, this is described in the Remarks section of the Array class overview.

You could add a cast:

return ((IEnumerable<T>)_array).GetEnumerator();

Note, older MSDN (pre docs.microsoft.com) coverage of this changed a few times with different .NET versions, check for the remarks section.

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