Interview question on C# implicit conversion

Question

I have been given a sample statement:

MyClass myclass = 3;

How is it possible to make this a valid statement? What code do I need to include in MyClass to support the implicit conversion from an int?

Answer 1

You need an implicit conversion operator:

public class MyClass
{
    private readonly int value;
    public MyClass(int value)
    {
        this.value = value;
    }

    public static implicit operator MyClass(int value)
    {
        return new MyClass(value);
    }
}

Personally I'm not a huge fan of implicit conversions most of the time. Occasionally they're useful, but think carefully before putting them in your code. They can be pretty confusing when you're reading code.

On the other hand, when used thoughtfully, they can be amazingly handy - I'm thinking particularly of the conversions from string to XName and XNamespace in LINQ to XML.