I was playing with the Unity Framework recently when I came across the following C# code sample on msdn:
IUnityContainer uContainer = new UnityContainer()
.RegisterType<IMyInterface, FirstObject>()
.RegisterType<MyBaseClass, SecondObject>();
MyObject myInstance = uContainer.Resolve<MyObject>();
This looked so much like the VB With syntax that I uncharitably assumed that the authors at MSDN had somehow confused C# and VB. After all, they had written this the standard C# syntax elsewhere:
// Create container and register types
IUnityContainer myContainer = new UnityContainer();
myContainer.RegisterType<IMyService, DataService>("Data");
myContainer.RegisterType<IMyService, LoggingService>("Logging");
// Retrieve an instance of each type
IMyService myDataService = myContainer.Resolve<IMyService>("Data");
IMyService myLoggingService = myContainer.Resolve<IMyService>("Logging");
C# developers with more than 8 or so years of experience can generally be broken down into two types who are mutually suspicious of one another: those who came up through the VB6 programming ranks and those who came up through C++ or Java. I did the former, and for the most part have never looked back. I don’t even get involved in disputes between C# lovers and VB lovers. They’re both nice language. I just happen to use the former for most things.
The one thing I do miss from VB, however, is the With command. It always seemed an elegant piece of syntactic sugar and easier to read when you find code that manipulates the same object repeatedly. My “you can’t do that on television” moment over the msdn sample code came out of that longing for something I thought I’d simply had to leave behind.
It took me a while to realize that the sample code was taking advantage of a trick that has always been available to C# developers but just not extensively used. (I even had to show it to several colleagues just to make sure I wasn’t just being slow – everyone’s first thought, blessedly, was that it was somehow a VB-to-C# translation mistake.) The trick is that the RegisterType method is returning an IUnityContainer object. Because a C# statement, unlike a VB statement, can be spread out over multiple lines in the editor until a semicolon delimiter is encountered, the code can be made to take on this VB-ish cast. In fact, the Append method of the StringBuilder type similarly returns its own container type, making the following code blocks equivalent:
StringBuilder sb = new StringBuilder();
// this code ...
sb.AppendLine("one");
sb.AppendLine("two");
sb.AppendLine("three");
// is equivalent to this ...
sb.AppendLine("one").AppendLine("two").AppendLine("three");
// is equivalent to this ...
sb.AppendLine("one")
.AppendLine("two")
.AppendLine("three");
This trick won’t work for properties, of course, but it is still pretty fun, and I’m kicking myself for never having come across it earlier.