What is the difference between
Foo<T> where T : BaseObject
and
Foo<BaseObject>
Isn't this statement the same?
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possible duplicate of [C# generic "where constraint" with "any generic type" definition?](http://stackoverflow.com/questions/1541152/c-sharp-generic-where-constraint-with-any-generic-type-definition) – Travis J May 13 '12 at 18:56
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2I don't see where the question is duplicate... – MUG4N May 13 '12 at 18:58
2 Answers
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No, it is not the same.
With:
Foo<T> where T : BaseObject
T can be any BaseObject type and its inheritors.
With:
Foo<BaseObject>
T must be BaseObject exactly (assuming no variance modifiers were declared in Foo for the generic type parameter).
Oded
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If BaseObject is an abstract class, then wont `InheritedObject` work for `Foo
` if `InheritedObject : BaseObject`? – Travis J May 13 '12 at 18:57 -
2@TravisJ - No, not unless covariance was declared on the generic type parameter. – Oded May 13 '12 at 18:59
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Consider this:
var list = new List<object>();
list.Add("Hello");
Console.WriteLine(list[0].Length); // doesn't compile
Similarly, with Foo<BaseObject>, consumers of Foo will only have access to the BaseObject members from Foo's T members. With Foo<T> where T : BaseObject, consumers of Foo will have access to all members of whatever derived type is actually passed for the type argument.
phoog
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