How to: Define a Class That Uses Members of an Existing Class

Artykuł
11/16/2012

You can use members of an existing class in another class that derives from it.

In the following example, suppose you want to define a special kind of Button that acts like a normal Button but also exposes a method that reverses the foreground and background colors.

To define a class that uses the members of an already existing class

Use a Class Statement (Visual Basic) to define a class from which to create the object you need.

Public Class reversibleButton

Be sure an End Class statement follows the last line of code in your class. By default, the integrated development environment (IDE) automatically generates an End Class when you enter a Class statement.
Follow the Class statement immediately with an Inherits Statement. Specify the class from which your new class derives.

Inherits System.Windows.Forms.Button

Your new class inherits all the members defined by the base class.
Add the code for the additional members your derived class exposes. For example, you might add a reverseColors method, and your derived class might look as follows:
```
Public Class reversibleButton
    Inherits System.Windows.Forms.Button
    Public Sub reverseColors() 
        Dim saveColor As System.Drawing.Color = Me.BackColor
        Me.BackColor = Me.ForeColor
        Me.ForeColor = saveColor
    End Sub
End Class 
```
If you create an object from the reversibleButton class, it can access all the members of the Button class, as well as the reverseColors method and any other new members you define on reversibleButton.

Compiling the Code

Be sure the compiler can access the class from which you intend to derive your new class. This might mean fully qualifying its name, as in the preceding example, or identifying its namespace in an Imports Statement (.NET Namespace and Type). If the class is in a different project, you might need to add a reference to that project. For more information, see Referencing Namespaces and Components.

Udostępnij za pośrednictwem

How to: Define a Class That Uses Members of an Existing Class

To define a class that uses the members of an already existing class

Compiling the Code

See Also

Tasks

Concepts

Dodatkowe zasoby