Pro C# 2010 and the .NET 4 Platform, Fifth Edition

10.6. Constraining Type Parameters

As this chapter illustrates, any generic item has at least one type parameter that you need to specify at the time you interact with the generic type or member. This alone allows you to build some type safe code; however, the .NET platform allows you to use the where keyword to get extremely specific about what a given type parameter must look like.

Using this keyword, you can add a set of constraints to a given type parameter, which the C# compiler will check at compile time. Specifically, you can constrain a type parameter as described in Table 10-6.

Table 10.6. Possible Constraints for Generic Type Parameters

Generic Constraint	Meaning in Life
where T : struct	The type parameter <T> must have System.ValueType ...