Dictionary is populated with an empty item after checking dictionary item in watch window

Question

Recently I've encountered a rather odd dictionary behaviour.

Sub DictTest()
    Dim iDict As Object
    Dim i As Integer
    Dim strArr() As String
    Set iDict = CreateObject("Scripting.Dictionary")
    strArr = Split("Why does this happen ? Why does this happen over and over ?", " ")
    For i = LBound(strArr) To UBound(strArr)
        iDict(strArr(i)) = strArr(i)
    Next
End Sub

The output is iDict populated with 7 items: But whenever I add watch:

It adds an empty item to a dictionary:

Why does adding a watch expression create an empty item in the dictionary?

Answer 1

If you examine the entry in the dictionary with a key of "What???" then naturally an entry must be created in the dictionary in order to show you that entry.

If you want to just check whether an entry exists, then perform a watch on iDict.Exists("What???").

Adding a watch is operating no differently to the following code:

Sub DictTest()
    Dim iDict As Object
    Dim i As Integer
    Dim strArr() As String
    Set iDict = CreateObject("Scripting.Dictionary")
    strArr = Split("Why does this happen ? Why does this happen over and over ?", " ")
    For i = LBound(strArr) To UBound(strArr)
        iDict(strArr(i)) = strArr(i)
    Next
    MsgBox "The value of the 'What???' entry in iDict is '" & iDict("What???") & "'"
End Sub

---

This changing of the contents of a Dictionary object is no different to using the Watch Window to change the value of x in the following situation:

In the above code, I used the watch window to edit the value of x from 5 to 10 prior to the Debug.Print statement.