Unique ways to use the null coalescing operator [closed]

Answer 1

I've used ?? in my implementation of IDataErrorInfo:

public string Error
{
    get
    {
        return this["Name"] ?? this["Address"] ?? this["Phone"];
    }
}

public string this[string columnName]
{
    get { ... }
}

If any individual property is in an "error" state I get that error, and otherwise I get null. It works really well.