How to Avoid Infinite Recursion When Overloading the '==' Operator with Null Checks?

Properly handle null checks to avoid infinite recursion in '==' operator overloads

When overloading the '==' operator, be sure to properly handle null checks to prevent infinite recursion. The code snippet provided in the question shows an incorrect approach:

<code>if (foo1 == null) return foo2 == null;</code>

This condition causes infinite recursion because the second call to == will again try to check if foo1 is empty, causing an infinite loop.

Correct code

To solve this problem and avoid infinite recursion, use object.ReferenceEquals for null checking:

<code>if (object.ReferenceEquals(foo1, null))
    return object.ReferenceEquals(foo2, null);</code>

This condition correctly handles the case where foo1 or foo2 (or both) is empty. Returns true if both operands are empty; returns false if one or both operands are not empty.

Full correction

The corrected code below incorporates this modification into the provided operator overload:

<code>public static bool operator ==(Foo foo1, Foo foo2) {
    if (object.ReferenceEquals(foo1, null))
        return object.ReferenceEquals(foo2, null);
    return foo1.Equals(foo2);
}</code>

With this change, operator overloading will be able to correctly handle null checks without causing infinite recursion.

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