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   ► KBTo/From GuidesASP ClassicLanguage Details  Print This     

Empty String Check (Cross Ref > Language Details)

By Mike Prestwood

ASP Classic versus PHP: A side by side comparison between ASP Classic and PHP.

 
Operators
 

A language symbol used for assignment, comparison, computational, or as a logical.

Empty String Check

[Other Languages] 

Languages Focus

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.

ASP Classic:   Len(s&vbNullString)

In ASP 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
  Response.Write("<br>Quotes with &'' say null is empty")
End If
 
If Len(s&"") = 0 Then
  Response.Write("<br>Len with &'' says null is empty")
End If
 
If Len(s&vbNullString) = 0 Then
  Response.Write("<br>Using vbNullString also works!")
End If
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