This print for content only-size & color not accurate 7" X 9-1/4" / casebound / malloy

// Error!

// Cannot convert type "T" to "Car"

public void PrintPetName(int pos)

{

Console.WriteLine(((Car)arCars[pos]).PetName);

}

This again does not compile, given that the compiler does not yet know the value of the type

parameter  and cannot guarantee the cast would be legal. Given the issues we have just exam-

ined, you might rightly wonder when (if ever) would you need to create a custom generic container?

Glad you asked!

Constraining Type Parameters Using the where Keyword

The major reason developers would author a custom generic collection type is to enforce con-

straints upon type parameters in order to build extremely type-safe containers. In C#, constraints

are applied using the where keyword, which can control the various characteristics of a type param-

eter (see Table 10-6).

C H A P T E R   1 0  

■

C O L L E C T I O N S   A N D   G E N E R I C S

334

8849CH10.qxd  9/25/07  4:17 PM  Page 334

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Table 10-6.

Possible Constraints for Generic Type Parameters