Example (note the case): string s = "Hello world!"; String s = "Hello world!"; What are the guidelines for the use of each? And what are the differences? string is an alias in C# for System.String. So technically, there is no difference. It's like int vs. System.Int32. As far as guidelines, it's generally recommended to use string any time you're referring to an object. e.g. string place = "worl..