Generics

All three languages support creating and using generics. Generics are discussed in Chapter 9.

For using generics C# borrowed the syntax from C++ templates to define the generic type with angle brackets. C++/CLI uses the same syntax. In Visual Basic, the generic type is defined with the Of keyword in braces.

 // C# List<int> intList = new List<int>(); intList.Add(1); intList.Add(2); intList.Add(3); // C++/CLI List<int>^ intList = gcnew List<int>(); intList->Add(1); intList->Add(2); intList->Add(3); ' Visual Basic Dim intList As List(Of Integer) = New List(Of Integer)() intList.Add(1) intList.Add(2) intList.Add(3) 

Because you use angle brackets with the class declaration, the compiler knows to create a generic type. Constraints are defined with the where clause.

  public class MyGeneric<T>    where T : IComparable<T> {    private List<T> list = new List<T>();    public void Add(T item)    {       list.Add(item);    }      public void Sort()    {       list.Sort();    } } 

Defining a generic type with C++/CLI is similar to defining a template with C++. Instead of the template keyword, with generics the generic keyword is used. The where clause is similar to that in C#; however, C++/CLI does not support a constructor constraint.

  generic <typename T> where T : IComparable<T> ref class MyGeneric { private:    List<T>^ list; public:    MyGeneric()    {       list = gcnew List<T>();    }    void Add(T item)    {       list->Add(item);    }    void Sort()    {       list->Sort();    } }; 

Visual Basic defines a generic class with the Of keyword. Constraints can be defined with As.

  Public Class MyGeneric(Of T As IComparable(Of T))    Private myList = New List(Of T)    Public Sub Add(ByVal item As T)       myList.Add(item)    End Sub    Public Sub Sort()       myList.Sort()    End Sub End Class