I talked about this one file utility here and here. I decided the syntax I create in the last improvement, for allowing the user to customize the exception to throw was not so usable, so I modified it. Now the resulting code to throw a specific exception is:

        /// 

        /// Classical not null verification, with custom 
        /// exception and message
        /// 
        /// 
        public void DoSomethingWithCustomMessage(string arg1)
        {
            Contract.Expect(() => arg1)
                .Throw((n)=>new Exception(string.Format("I'm unhappy to see that {0} is null",n)))
                .WhenViolate
                .IsNotNull();
        }

So there is no more any magic formatting, we just need to provide a function returning some kind of exception. The lambda argument (n) is the literal representing the name argument. I also added a wiki page on the project repository, to show the basic usage of the library so at a glance you can see how it works.