Executing code when setting properties

You can create Property Let, Property Set, and Property Get procedures that share the same name. By doing this, you can create a group of related procedures that work together. After a name is used for a Property procedure, that name can't be used to name a Sub or Function procedure, a variable, or a user-defined type.

The Property Let statement allows you to create a procedure that sets the value of the property. One example might be a Property procedure that creates an inverted property for a bitmap on a form.

This is the syntax used to call the Property Let procedure.

Form1.Inverted = True

The actual work of inverting a bitmap on the form is done within the Property Let procedure.

Private IsInverted As Boolean
 
Property Let Inverted(X As Boolean)
    IsInverted = X
    If IsInverted Then
        …
        (statements)
    Else
        (statements)
    End If
End Property

The form-level variable stores the setting of your property. By declaring it Private, the user can only change it by using your Property Let procedure. Use a name that makes it easy to recognize that the variable is used for the property.

This Property Get procedure is used to return the current state of the property.

Property Get Inverted() As Boolean
    Inverted = IsInverted
End Property

Property procedures make it easy to execute code at the same time that the value of a property is set. Use property procedures to do the following processing:

• Before a property value is set to determine the value of the property.
• After a property value is set, based on the new value.