C# implicit type conversion (see http://msdn.microsoft.com/en-us/library/zk2z37d3.aspx for a more detailed explanation)

csharp_implicit_type_conversion.cs

    public class ImplicitConversionTest
    {
        public class A
        {
            public string Member { get; set; }

            public static implicit operator string(A self)
            {
                return self.Member;
            }
        }

        public class B
        {
            public B(string value)
            {
                Member = value;
            }

            public string Member { get; private set; }
        }

        [Test]
        public void Test()
        {
            var a = new A { Member = "foo"};

            var b = new B(a); // a will be implicitly converted into a string!

            Assert.That(b.Member, Is.EqualTo(a.Member));
        }
    }