Update Dimensional Concurrent Dictionary - vb.net

Question

I have this little function that I found but I am having a hard time trying to call it correctly. how can I call it to update my ConcurrentDictionary
Public Class Form1
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim Animals As New Concurrent.ConcurrentDictionary(Of String, String())
Dim iKey = "key123456"
Animals(iKey) = {"cat", "dog", "bird"}
Dim success As Boolean = TryUpdate(Animals, iKey, Func("cat", "frog"))
End Sub
Function TryUpdate(Of TKey, TValue)(dict As Concurrent.ConcurrentDictionary(Of TKey, TValue), key As TKey, updateFactory As Func(Of TValue, TValue)) As Boolean
Dim curValue As TValue
If Not dict.TryGetValue(key, curValue) Then
Return False
End If
dict.TryUpdate(key, updateFactory(curValue), curValue)
Return True
End Function
End Class

Answer 1

TryUpdate has three parameters,
the ConcurrentDictionary to be updated,
the Key to be updated in the dictionary, and
a delegate function that accepts the key's current value, and returns the desired value.
Dim success As Boolean = TryUpdate(myDictionary, myKey, Func(oldval) newval)
How you pass the third parameter is up to you, but it looks like the intention is so you can have a look at the old value to ensure it is what you expected, then passing either your new value, or the returned value accordingly.
Addition for clarity: The third parameter is expecting to be passed a delegate to a function which will accept the current value of the key you are trying to change, and return a new value (or the original value, if you don't want to change it).
Here I'm creating a function CheckValue that determines if the old value is what I expected, then if so returns the new value. The myDel is a delegate of that function which is passed into TryUpdate.
Dim whatIExpected As String = ""
Dim newVal As String = ""
Dim myDel As Func(Of String, String) = AddressOf CheckValue
Public Function CheckValue(ByVal oldVal As String) As String
If (oldVal = whatIExpected) Then
Return newVal
Else
Return oldVal
End If
End Function
'Then later inside some function or sub..
whatIExpected = "cat"
newVal = "frog"
Dim success As Boolean = TryUpdate(myDictionary, myKey, myDel)