Datachanged property in vb what are classes

Walkthrough: Defining Classes (Visual Basic)

This walkthrough shows how to define classes that you can then use to create objects. It also shows how to add properties and methods to the new class and how to initialize an object.

Note

You may see different names or locations for the Visual Studio user interface elements on your computer than those listed in the following instructions. These elements depend on the particular Visual Studio version and the settings used. For more information, see Personalizing the IDE.

How to define a class

  1. Create a project by going to the menu file on New project click. The dialog box New project is displayed.

  2. Select Windows Application from the list of Visual Basic project templates to view the new project.

  3. Add a new class to the project by going to the menu Project on Add class click. The dialog box Add new item is displayed.

  4. Choose the Classes Template.

  5. Name the new class, then click Add to view the code for the new class.

    Note

    You can use the Visual Basic Code editor to add a class to the startup form by entering the keyword followed by the name of the new class. The Code editor provides a corresponding instruction for you.

  6. Define a private field for the class by adding the following code between the -and statements:

    Declaring the field means that it can only be used within the class. You can expose fields outside of a class by using access modifiers such as, which provide more access. For more information, see Access Levels in Visual Basic.

  7. Define a property for the class by adding the following code:

  8. Define a method for the class by adding the following code:

  9. Define a parameterized constructor for the new class by adding a procedure named:

    The constructor is called automatically when an object is created based on this class. This constructor sets the value of the field that contains the username.

Here's how to create a button to test the class

  1. Change the startup form to design mode by clicking in Solution Explorer right click on the name and then Show on designer click. By default, the start form for Windows application projects is named Form1. vb. The main form will then be displayed.

  2. Add a button to the main form and double-click it to see the code for the event handler. Add the following code to call the test procedure:

How to run your application

  1. Run the application by pressing F5. Click the button on the form to invoke the test procedure. A message appears stating that the original is "Moore, Bobby" because the procedure called the object's method.

  2. click on OKto close the message box. The procedure changes the value of the property and displays a message stating that the new value is "has Joe".

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