PerformClick is one of the many casualties of a move from Windows Forms to WPF. Of course, it's probably not something you would need to use often, but just in case you do then there is a way.
It's not a very intuitive way and - had it not been that I spotted the C# version of this trick in Adam Nathan's WPF book - I wouldn't be sat here writing this now. I'd still be searching endlessly to try and find the answer.
In order to achieve this in VB, you need to do the following:
Add a Reference to UIAutomationProvider in your Project.
Add an Imports statement:
Add another Imports statement:
Use the following code snippet:
Dim buttonPeer As New ButtonAutomationPeer(Button1)
Dim invokeProv As IInvokeProvider = TryCast(buttonPeer.GetPattern(PatternInterface.Invoke), IInvokeProvider)
The above code to be placed wherever you want to simulate the Button's Click. (Change the Button name as needed).
It did occur to me that this task might be a good candidate for a custom Command, using WPF's quite versatile Command abilities. However, I haven't got past the "wonder if that's a good idea?" stage. And to be honest, probably won't any time soon.
Whether you feel that it's necessary to go to the trouble of the Automation or the Command approach is of course entirely up to you. I have to admit to being tempted simply to move the action code out of the Button Click event and into a separate method that can be called from both the Button Click and other events. But then, I've never been much or a purist about these things.