1_RA

Event Handlers

I prefer C# over VB.net, since I never had experience with it. While, C# is quite similiar to languages that I tried before (C, C++, Java).

During the application exercies we had an opportunity to see the differences in event handling between these two languages.

C#

In C#, classes manage event handlers (i.e. DragDrop, DragEnter, MouseLeave, MouseEnter, Click) by subscribing to that events via:

<some class>.Event += new <some event handler>()

It also might require to add an callback function when subscribing to a certain event, such that:

<some class>.Event += new <some event handler>(< some callback function>)

Check Form1.Designer.cs, for example:

this.button1.Click += new System.EventHandler(this.button1_Click)

Callback functions are functions that are invoked when a certain event occurs. Thus, when button1 is clicked it will call the button1_Click function.

Check the references [1, 2] for more detailed overview.

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VB.net

In VB.net, event handling can be done in two ways: via AddHandler or Handler/WithEvents [3]. In the first case, it is quite similar to C#:

AddHandler <some class>.Event, AddressOf <some callback function>

Then define callback function.

In the second case, it is done during the definition of the callback function (which can be seen in Form1.vb). So it's quite compact.

Sub <Callback function name>(...) Handles <some class>.Event

---some code---

End Sub

Check Form1.vb, for example:

Private Sub Button1_Click(...) Handles Button1.Click

---some code---

End Sub

Check the references [1-3] for more detailed overview.

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References

1. https://sites.harding.edu/fmccown/vbnet_csharp_comparison.html#events

2. https://www.microfocus.com/documentation/enterprise-developer/ed30/VS2017/GUID-A682E979-5242-4862-80C2-BF57FB69C088.html

3. https://docs.microsoft.com/en-us/dotnet/visual-basic/programming-guide/language-features/procedures/how-to-call-an-event-handler