The "is" keyword and the override of Equals method

Question

The documentation for the keyword "is" states that:

The is operator only considers reference conversions, boxing conversions, and unboxing conversions. Other conversions, such as user-defined conversions, are not considered.

What does it mean in practice? Is it wrong to use it to check if a struct is a certain type? For example,

public struct Point2D
{
    public int X;
    public int Y;

    ...

    public override bool Equals(Object value)
    {
        if (value != null && value is Point2D)   // or if (value != null && GetType() == value.GetType())
        {
            Point2D right = (Point2D)value;
            return (X == right.X && Y == right.Y);
        }
        else return false;
    }

    ...
}

It is wrongish, value.GetType() == typeof(Point2D) protects you against refactoring accidents. — Hans Passant, Feb 08 '12 at 00:59
Is [this](http://stackoverflow.com/questions/983030/type-checking-typeof-gettype-or-is) the reason? — enzom83, Feb 08 '12 at 13:39
@enzom83 That is correct. `is` could be appropriate for this case, if you care about inheriting from Point2D, and want children to also have this same logic (by default) — McKay, Feb 08 '12 at 16:09

score 6 · Accepted Answer · answered Feb 07 '12 at 23:57

Checking whether a struct is a certain type is fine. The documentation means that user-defined explicit and implicit conversion operators are not evaluated when considering whether the given object is of the specified type, even if there is a user-defined operator that can convert it to said type.

The "is" keyword and the override of Equals method

1 Answers1