Question

how can i know what event was triggered in picturebox in VBnet?

in vbnet code:

Private Sub picButton_MouseEnter(ByVal sender As Object, ByVal e As System.EventArgs) Handles picButton.MouseEnter
    'CODE HERE'
End Sub

Private Sub picButton_MouseLeave(ByVal sender As Object, ByVal e As System.EventArgs) Handles picButton.MouseLeave
    'CODE HERE'
End Sub

and i want to make it like this:

Private Sub picButtonEVent(ByVal sender As Object, ByVal e As System.EventArgs) Handles picButton.MouseLeave, picButton.MouseEnter
    'CODE HERE'
    'If MouseEnter Then'
        'Code for mouseEnter'
    'ElseIf MouseLeave Then'
        'Code for mouseLeave'
    'End If'
End Sub

i want to know what event was triggered whether it is .MouseEnter or .MouseLeave. the reason why i’m making this is to make the code more categorized according to the object that was used.

Answer 1

One thing you could do is to create a helper function that takes an additional Enum parameter that you can use to determine the event type, and then you can just enclose the dummy events in a region so you can collapse them. Off-hand, I don’t know of an elegant way to determine what event actually fired from the event itself (that is, without using Reflection…)

My suggestion:

Private Sub picButton_MouseEnter(ByVal sender As Object, ByVal e As System.EventArgs) Handles picButton.MouseEnter
    UniversalEvent(this, e, EventType.MouseEnter)
End Sub

Private Sub picButton_MouseLeave(ByVal sender As Object, ByVal e As System.EventArgs) Handles picButton.MouseLeave
    UniversalEvent(this, e, EventType.MouseLeave)
End Sub

Private Sub UniversalEvent(ByVal sender As Object, ByVal e As System.EventArgs, ByVal eventType As EventType)
    If MouseEnter Then
        'Code for mouseEnter'
    ElseIf MouseLeave Then
        'Code for mouseLeave'
    End If'
End Sub

Edit:

As mentioned before, Reflection is a possibility, though not ideal due to the amount of overhead involved (especially in the case of events like these which could be called quite frequently). That being said, I whipped up a working example using Reflection simply to illustrate that it’s possible. (Actually StackTrace, which is what I used, is in System.Diagnostics. Not exactly Reflection but it’s close enough for me…)

Please don’t send the raptors…

Public Class Form1

    Private Sub PictureBox_Events(ByVal sender As System.Object, ByVal e As System.EventArgs) _
        Handles PictureBox1.MouseLeave, PictureBox1.MouseEnter

        Select Case GetEventType(New StackTrace())
            Case EventType.MouseEnter
                Console.WriteLine("Enter")
            Case EventType.MouseLeave
                Console.WriteLine("Leave")
            Case Else
                Console.WriteLine("Dunno")
        End Select

    End Sub

    Private Function GetEventType(ByRef callStack As StackTrace) As EventType
        'I laugh in the face of NullReferenceExceptions...'
        Dim callerName As String = callStack.GetFrames()(1).GetMethod().Name

        If "OnMouseEnter".Equals(callerName, StringComparison.OrdinalIgnoreCase) Then
            Return EventType.MouseEnter
        ElseIf "OnMouseLeave".Equals(callerName, StringComparison.OrdinalIgnoreCase) Then
            Return EventType.MouseLeave
        End If

        Return EventType.Dunno

    End Function

    Enum EventType
        Dunno
        MouseEnter
        MouseLeave
    End Enum

End Class