An empty string is a zero length string, a string that is equal to null (""), or not assigned. In some languages, you can check if a string is empty by comparing it to an empty string (""). Some languages distinguish between nil and null ("") so checking if the length is 0 is easier.
VB Classic Empty String Check
In VB Classic, you have to add an empty string to the value being compared in order to get consistent results. For example, add &"" to your string varilable or it's code equivalent &vbNullString. Then compare to an empty string or verify it's length to 0 with Len.
Syntax Example:
All these will work for variables unassigned, set to "", or set to Null:
If s&"" = "" Then MsgBox ("Quotes with &'' say null is empty") End If
If Len(s&"") = 0 Then MsgBox ("Len with &'' says null is empty") End If
If Len(s&vbNullString) = 0 Then MsgBox ("Using vbNullString also works!") End If
VB Classic
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To/From Code Guide: 
