#570 – Assignment Compatibility for Reference Types

A reference type is assignment compatible if the value being assigned belongs to a type that is either the same as, or is a derived type of, the type of the storage location being assigned to.  You can assign a variable of type T to a storage location of type U if T is a narrower type than U, or is the same type as U.

Hound huck = new Hound("Huckleberry", 55);

// Since Hound is a sub-class of Dog, we can
// assign to a variable of type Dog
Dog dog1 = huck;

In this case, the variable of type Dog will still be pointing to an instance of a Hound.  The assignment doesn’t change anything about the object.

To see this, construct an instance of a Dog directly and then compare the objects.

// This one points to an actual Dog instance
Dog dog2 = new Dog("Just some dog", 2);

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About Sean
Software developer in the Twin Cities area, passionate about software development and sailing.

2 Responses to #570 – Assignment Compatibility for Reference Types

  1. Pingback: #574 – The Problem with Array Covariance « 2,000 Things You Should Know About C#

  2. Pingback: #575 – Using the is Operator to Check the Type of a Reference-Typed Object « 2,000 Things You Should Know About C#

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