Event and Exception Changes for Visual Basic 6?

[jhon]

Hi friends,
I have recently started with the Visual Basic and so I am not having much idea about it. I want to know about the Event and Exception Changes that occurs in VB. So please explain me about an Event and Exception Changes for Visual Basic 6? Help me as soon as possible.!!

[Warner]

Events and exceptions are class members that are used to signal changes in the class to the client code. Typically, an event signals an expected change, and the client code can choose to respond or not. Exceptions signal an error state, and the client code ignores this at its own risk. The syntax for declaring an event has not changed from Visual Basic 6.0 :

Public Event StateChanged()

[Reegan]

Exceptions are not supported in Visual Basic 6.0, but raising an error is. Errors are caught using On Error GoTo statements in conjunction with labeled statements. Try...Catch...Finally Statement (Visual Basic) block structure is used to respond to exceptions. An example is shown below :

Dim big As Integer = Integer.MaxValue
Dim bigger As Integer = Integer.MaxValue
Try
    Dim biggest As Integer = big + bigger
Catch ex As Exception
    MsgBox("Addition did not succeed.")
End Try

[Zecho]

Code that raises errors in Visual Basic 6.0 is converted to code that raises errors in Visual Basic 2005. Here is an example of converted code that raises an error :

Private mvarAge As Short
Public Property Age() As Short
    Get
        Age = mvarAge
    End Get
    Set(ByVal Value As Short)
        If Value >= 0 Then
            mvarAge = Value
        Else
            Err.Raise(vbObjectError + 2, Me, _
                "Age must be greater than or equal to zero.")
        End If
    End Set
End Property

[Katty]

Using an exception instead requires only replacing the Err.Raise call with a Throw Statement (Visual Basic). Another benefit is that the error number can be eliminated. When upgrading events and exceptions to Visual Basic, consider the following :

• Replacing On Error GoTo statements with Try statements.
• Replacing Err.Raise with Throw
• Using the parameter conventions for events (Public Event StateChanged(ByVal sender As Object, ByVal e As EventArgs)).
• Creating custom exceptions and EventArgs classes through inheritance.