Dim rs as Recordset
Set rs as New Recordset
 
'... a lot of coding ...
 
if Err.Number <> 0 Then ' oops,something gone wrong!
    If rs.State <> adStateClosed Then rs.Close
    Set rs = Nothing
end if
 
' I want to evaluate if rs is Nothing,or Null
 
if rs is Nothing then 
' this doesn't throw errors,and works well :D
end if
 
if rs is Null then
' this throws an error of "types not compatible"
end if
 
if rs = Null then
' this throws an error of "types not compatible"
end if
 
if isNull(rs) then
' never enters here,isNull(rs) evaluates to False
end if

我发现在VB6中我很少使用“Null”(我用它来评估空记录集模式名称),但我对图像,adodb.connections或记录集之类的东西使用“Nothing”.对于字符串我有vbNullString.我读到它是一个指向空字符串的指针.

“Null”是“未知变量值”而“Nothing”是真正的空值吗？