Error checking for NULL in VBScript

Question

I have the following VBScript in a Classic ASP page   function getMagicLink fromWhere  provider      dim url      url    magic asp fromwhere    amp  fromWhere     If Not provider is Nothing Then   Error occurs here         url   url  amp    amp provider    amp  provider      End if     getMagicLink     lt a target   blank  href     amp  url  amp     gt    amp  number  amp    lt  a gt   end function   I keep getting an  Object Required  error messager on the line that says If Not provider Is Nothing Then   Either the value is NULL  or it s not NULL  so why am I getting this error   Edit  When I invoke the object  I pass in either NULL  or I pass in a string

User · Accepted Answer

From your code  it looks like provider is a variant or some other variable  and not an object   Is Nothing is for objects only  yet later you say it s a value that should either be NULL or NOT NULL  which would be handled by IsNull     Try using   If Not IsNull provider  Then      url   url  amp    amp provider    amp  provider  End if   Alternately  if that doesn t work  try   If provider  lt  gt     Then      url   url  amp    amp provider    amp  provider  End if

User · Answer

I see lots of confusion in the comments  Null  IsNull   and vbNull are mainly used for database handling and normally not used in VBScript  If it is not explicitly stated in the documentation of the calling object data  do not use it    To test if a variable is uninitialized  use IsEmpty    To test if a variable is uninitialized or contains     test on    or Empty  To test if a variable is an object  use IsObject and to see if this object has no reference test on Is Nothing   In your case  you first want to test if the variable is an object  and then see if that variable is Nothing  because if it isn t an object  you get the  Object Required  error when you test on Nothing   snippet to mix and match in your code   If IsObject provider  Then     If Not provider Is Nothing Then           Code to handle a NOT empty object   valid reference     Else           Code to handle an empty object   null reference     End If Else     If IsEmpty provider  Then           Code to handle a not initialized variable or a variable explicitly set to empty     ElseIf provider      Then           Code to handle an empty variable  but initialized and set to         Else           Code to handle handle a filled variable     End If End If

User · Answer

I will just add a blank      to the end of the variable and do the comparison   Something like below should work even when that variable is null   You can also trim the variable just in case of spaces   If provider  amp      lt  gt     Then      url   url  amp    amp provider    amp  provider  End if

[asp-classic] Error checking for NULL in VBScript

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