C# in Depth

Advanced generics95REFLECTING GENERIC METHODSGeneric methods have a similar (though smaller) set of additional properties andmethods. Listing 3.12 gives a brief demonstration of this, calling a generic method byreflection.Listing 3.12Retrieving and invoking a generic method with reflectionpublic static void PrintTypeParameter(){Console.WriteLine (typeof(T));}...Type type = typeof(Snippet);MethodInfo definition = type.GetMethod("PrintTypeParameter");MethodInfo constructed;constructed = definition.MakeGenericMethod(typeof(string));constructed.Invoke(null, null);First we retrieve the generic method definition, and then we make a constructedgeneric method using MakeGenericMethod. As with types, we could go the other way ifwe wanted to—but unlike Type.GetType, there is no way of specifying a constructedmethod in the GetMethod call. The framework also has a problem if there are methodsthat are overloaded purely by number of type parameters—there are no methodsin Type that allow you to specify the number of type parameters, so instead you’d haveto call Type.GetMethods and find the right one by looking through all the methods.After retrieving the constructed method, we invoke it. The arguments in this exampleare both null as we’re invoking a static method that doesn’t take any “normal”parameters. The output is System.String, as we’d expect.Note that the methods retrieved from generic type definitions cannot be invokeddirectly—instead, you must get the method from a constructed type. This applies toboth generic methods and nongeneric methods.Again, more methods and properties are available on MethodInfo, and IsGeneric-Method is a good starting point in MSDN. Hopefully the information in this section willhave been enough to get you going, though—and to point out some of the added complexitiesyou might not have otherwise anticipated when first starting to access generictypes and methods with reflection.That’s all we’re going to cover in the way of advanced features. Just to reiterate,this is not meant to have been an absolutely complete guide by any means—but mostdevelopers are unlikely to need to know the more obscure areas. I hope for your sakethat you fall into this camp, as specifications tend to get harder to read the deeper yougo into them. Remember that unless you’re working alone and just for yourself,you’re unlikely to be the only one to work on your code. If you need features that aremore complex than the ones demonstrated here, you almost certainly shouldn’tassume that anyone reading your code will understand it without help. On the otherhand, if you find that your coworkers don’t know about some of the topics we’ve coveredso far, please feel free to direct them to the nearest bookshop…Licensed to Rhona Hadida