sybe
asked on
discussion: avoinding and using "On Error Resume Next"
offspin from https://www.experts-exchange.com/questions/20935064/problem-of-compare-the-value-of-the-date-system-and-the-date-we-pick-from-list-box.html
In my opinion one shoud not use "On Error Resume Next" for a complete ASP page. In some (rare) situations it has a use within funcions, like with XML.
Most errors can be trapped using the native IsDate(), IsNumeric(), IsObject(), TypeName(), FSO.FileExists etc functions.
Some functions that are not native in VBScript can be created, like
- IsEmail(), to check is a string is a valid email address
- IsXML(), the MSXML object has it's own error trapping
I think it is an important issue because I see many (starting?) programmers using "On Error resume Next" at the top of their code. And I have the habit of remarking that "don't do that".
Any opinions?
(points will be distributed among meaningfull/contributing comments)
In my opinion one shoud not use "On Error Resume Next" for a complete ASP page. In some (rare) situations it has a use within funcions, like with XML.
Most errors can be trapped using the native IsDate(), IsNumeric(), IsObject(), TypeName(), FSO.FileExists etc functions.
Some functions that are not native in VBScript can be created, like
- IsEmail(), to check is a string is a valid email address
- IsXML(), the MSXML object has it's own error trapping
I think it is an important issue because I see many (starting?) programmers using "On Error resume Next" at the top of their code. And I have the habit of remarking that "don't do that".
Any opinions?
(points will be distributed among meaningfull/contributing comments)
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>>we have the error object that allows us to test for errors<
Unfortunately, unless you use On Error Resume Next the Error object will not be much use to you.
Unfortunately, unless you use On Error Resume Next the Error object will not be much use to you.
ASKER
I have a few examples where I use On Error Resume Next in a function. Because I don't know how to do what i want in an other way.
<%
' is there another way to get the dimension of an array???
Function GetArrayDimension(ByVal aArray, ByVal iMax)
Dim iCount, iTest
On Error Resume Next
For iCount = 1 To iMax
iTest = UBound(aArray,iCount)
If Err Then Exit For
Next
GetArrayDimension = iCount -1
Err.Clear
End Function
%>
<%
' create a connection. There used to be some strange bug in IIS that would with irregular interval require
' "DSN=" before the actual connecion string. The code below is ages old, and i haven't checked it's necessity for a long time
Function MakeDSNConnection(sDSN)
Dim oConn
Set oConn = Server.Createobject("ADODB
On Error Resume Next
oConn.Open sDSN
If Err Then
Response.write Err.description & "<br>"
sDSN = "DSN=" & sDSN
oConn.Open sDSN
End If
Set MakeDSNConnection = oConn
End Function
%>
<%
' find out if an object is a Collection
Function IsCollection(ByVal oVar)
On Error Resume Next
Dim element, vTest
IsCollection = False
For each element In oVar
If Err Then
Err.Clear
Exit Function
Else
vTest = oVar(element)
If Err Then
Err.Clear
Exit Function
Else
IsCollection = True
Exit Function
End If
End If
Next
Err.Clear
End Function
%>
<%
' is there another way to get the dimension of an array???
Function GetArrayDimension(ByVal aArray, ByVal iMax)
Dim iCount, iTest
On Error Resume Next
For iCount = 1 To iMax
iTest = UBound(aArray,iCount)
If Err Then Exit For
Next
GetArrayDimension = iCount -1
Err.Clear
End Function
%>
<%
' create a connection. There used to be some strange bug in IIS that would with irregular interval require
' "DSN=" before the actual connecion string. The code below is ages old, and i haven't checked it's necessity for a long time
Function MakeDSNConnection(sDSN)
Dim oConn
Set oConn = Server.Createobject("ADODB
On Error Resume Next
oConn.Open sDSN
If Err Then
Response.write Err.description & "<br>"
sDSN = "DSN=" & sDSN
oConn.Open sDSN
End If
Set MakeDSNConnection = oConn
End Function
%>
<%
' find out if an object is a Collection
Function IsCollection(ByVal oVar)
On Error Resume Next
Dim element, vTest
IsCollection = False
For each element In oVar
If Err Then
Err.Clear
Exit Function
Else
vTest = oVar(element)
If Err Then
Err.Clear
Exit Function
Else
IsCollection = True
Exit Function
End If
End If
Next
Err.Clear
End Function
%>
Those are all good exceptions to my rule of never use On Error Resume Next.
>is there another way to get the dimension of an array???
Yes: http://vbnet.mvps.org/index.html?code/helpers/getarraydims.htm
>find out if an object is a Collection
Can't think of another way of doing that but I've never come across a situation where such basic type info is now already known.
Yes: http://vbnet.mvps.org/index.html?code/helpers/getarraydims.htm
>find out if an object is a Collection
Can't think of another way of doing that but I've never come across a situation where such basic type info is now already known.
in ASP 2 maybe but we have the error object that allows us to test for errors - anyhow I'd argue that On Error doesn't allow us to detect errors it allows us to sort of supress them.
Steve