[RESOLVED] Get control from its event

[squatman]

Hi there,

I have 3 labels that I am setting a MouveEnter and MouseLeave Event to change the BackColor.

Rather than writing Label1.BackColor = Color.Red in Label1_MouseEnter, Label2.BackColor = Color.Red in Label2_MouseEnter etc. and similar for the MouseLeave Event, is there a way of determining the name of the control from the Event. I was hoping for something like sender.BackColor = Color.Red but this wasn't right.

Thank you.

[Shaggy Hiker]

The sender argument IS the control. You just have to cast it. So, you can do this:

dim myLabel = DirectCast(sender, Label)

And now you'll have your control to work with.

Alternatively, you can do something like this:

DirectCast(sender,Label).BackColor = Color.Red

Which is close to what you were doing, except that you were leaving sender as type Object, which won't have a BackColor property. You have to do the cast to convert it to the right type.

[squatman]

Thanks a lot Shaggy!

[squatman]

Is there a way to determine if it was the MouseEnter or MouseLeave Event?

[Shaggy Hiker]

No, there's no easy way to do that other than to have one method for MouseEnter and a different method for MouseLeave. An event is really just a list of methods maintained by the object that raises the event. The object maintains a list for each event it raises. When the action that triggers the event occurs, the object goes through the list of methods and calls each one in turn. So, when you create a method to handle an event, all you are really doing is passing the address of the event to the object that will raise the event, and the object (a control, in this case) simply adds the method to a list.

When the event is raised, the object provides itself as the first argument. That lets you know WHO raised the event, but not WHY the event was raised. It is assumed that you will determine that by organization alone. If you don't care what the event was, pass the same method to all the events. If you DO care which event it was, you'll need a different method for each event.

[squatman]

Shaggy,

Thank you very much for that, but all it was is:

I have my events:

Private Sub lblDocumentsTab_MouseEnter(sender As Object, e As EventArgs) Handles lblDocumentsTab.MouseEnter
        lblHover(DirectCast(sender, Label), 1)
    End Sub
 
    Private Sub lblDocumentsTab_MouseLeave(sender As Object, e As EventArgs) Handles lblDocumentsTab.MouseLeave
        lblHover(DirectCast(sender, Label), 0)
    End Sub
 
 
    Private Sub lblHover(lbl As Label, switch As Integer)
        If switch = 1 Then
            If lbl.BackColor = Color.WhiteSmoke Then
                lbl.BackColor = Color.FromArgb(216, 234, 249)
            End If
        Else
            If lbl.BackColor = Color.FromArgb(216, 234, 249) Then
                lbl.BackColor = Color.WhiteSmoke
            End If
        End If
    End Sub

Rather than using "switch" as Integer, I wondered if that could perhaps be a String that said "Enter" or "Leave", that way the code within the MouseEnter and MouseLeave could be exactly the same, something like:

Private Sub lblDocumentsTab_MouseEnter(sender As Object, e As EventArgs) Handles lblDocumentsTab.MouseEnter
        lblHover(DirectCast(sender, Label), EventName.ToString)
    End Sub
 
    Private Sub lblDocumentsTab_MouseLeave(sender As Object, e As EventArgs) Handles lblDocumentsTab.MouseLeave
        lblHover(DirectCast(sender, Label), EventName.ToString)
    End Sub

Thank you.

[Shaggy Hiker]

I like the integer approach better. What do you gain by using a string? You'd still need to have a switch or If statement in lblHover.

However, if what you showed is all that lblHover has to do, then you don't need the switch at all, nor do you need the event name. After all, the logic is:

If the color is WhiteSmoke Then
change it to the other color.
Else
change it to WhiteSmoke
End If

Then it doesn't seem to matter what the event is.

[i00]

If there were multiple I would suggest an Enum, but in the case with two states I would suggest a bool eg:

Private Sub lblHover(lbl As Label, Entering As Boolean)

Kris