New Features in C# 2.0—Type-Safe List: What about

Microsoft .NET Framework, ASP.NET, Visual C# (CSharp, C Sharp, C-Sharp) Developer Training, Visual Studio

What about…

…if you try to add an integer to the list of Employees?

Try it. Start by uncommenting the following line in Example 1-1 and recompiling the program:

empList.Add(i * 5);

You’ll get a pair of compile errors:

Error 1 The best overloaded method match for 'System.Collections.
Generic.List<ListCollection.Employee>.Add(ListCollection.Employee)' has some invalid arguments
Error 2 Argument '1': cannot convert from 'int' to
'ListCollection.Employee'

The information provided in these two compile errors enable you to determine that it is not legal to add an int to a collection of Employee objects because no implicit conversion or subtype relationship exists from one to the other.

The good news is that this is a compile error, rather than a runtime error, which can sneak out the door and happen only when your client runs the application!

…what about other generic collections; are any available?

Other generic collections are available as well. For instance, the Stack and Queue collections, as well as the ICollection interface, are available in type-safe versions in .NET 2.0.

You use these just as you would List<T>. For example, to make a stack of Employee objects, you replace T in the Stack definition (Stack<T>) with the Employee type:

Stack<Employee> employeeStack = new Stack<Employee>( );