Exception Handling in Collection - Suggestions ?

[MikeCallon]

Hi there,

I've created a collection class, but what's the best way of handling an exception that occurs when the user of the class requests an invalid item from the collection ?

So in the Example below, what's the best way of handling the situation where the user of this class passes an iIndex greater that the number of items in the collection ?

Default Public ReadOnly Property Item(ByVal iIndex As Integer) As ProductSpecParameter
  Get            
    Return CType(List.Item(iIndex),ProductSpecParameter)
  End Get
End Property

Any comments / suggestions would be greatly appreciated

 

[TipGiver]

Two ways:

1. If iIndex > List.Items.Count -1 then
Return Nothing
' throw new exception ("item not found") ' ?
Else
Return CType(List.Item(iIndex),ProductSpecParameter)
End If


2. Use Try Catch block, but no use because you are able to know the possible 'error' using a simple If/Else block.

 

[earthandfire]

TipGiver, will the exception ever be thrown?

1. If iIndex > List.Items.Count -1 then
Return Nothing
' throw new exception ("item not found") ' ?


perhaps:

1. If iIndex > List.Items.Count -1 then
' throw new exception ("item not found") ' ?
Return Nothing


Hope this helps.

 

[TipGiver]

No, because it is under the the return, you are right! But i took care of it.. commenting that line, heh

 

[TipGiver]

Hmmm, the '-1' should be deleted ,or '>' should be '>='

 

[MikeCallon]

Thanks for the pointers guys....

While we're at it - what if iIndex is < 0

 

[TipGiver]

If (iIndex >= 0) AND (iIndex < List.Items.Count) then
' ok!
Else
' not found
End If


or use the select case

Select Case iIndex
Case 0 To List.Items.Count - 1
' ok!
Case Else
' not found
End Select

 

[ThatRickGuy]

Or you could just not check or catch it. As soon as your class tries to get the iItem indexed object, it should throw an index out of range exception that will be passed up to the calling method.

-Rick

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