CType and Type casting Exception

Question

Public Property Duration() As Integer
Get
  Try
    Return CType(Item(DurationColumn), Integer)
  Catch e As Global.System.InvalidCastException
    Throw New Global.System.Data.StrongTypingException("The value for column 'Duration' in table 'T_MembershipSale' is DBNull.", e)
  End Try
End Get
Set(ByVal value As Integer)
  Item(DurationColumn) = value
End Set
End Property

What happens when a user wants to allocate "" as Item(DurationColumn) to integer? I get an exception. Any clean solution to avoid this and set 0 for ""?

Jim Mischel · Answer 1 · 2011-02-25T18:18:40.110

3

Use Int32.TryParse:

Dim number as Integer
If Not Int32.TryParse(DurationColumn, number) Then number = 0
return number

This handles the case of "", as well as any other invalid value (i.e. non-number) the user might enter.

edited Feb 25 '11 at 18:18

answered Feb 25 '11 at 17:30

Jim Mischel

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To me, this is the clean way to do it. – XIVSolutions Feb 26 '11 at 08:05

score 0 · Answer 2 · edited Feb 28 '11 at 13:05

0

Look at TryCast and Int32.TryParse.

edited Feb 28 '11 at 13:05

Cody Gray - on strike

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answered Feb 25 '11 at 17:33

Rob P.

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score 0 · Answer 3 · edited Nov 13 '12 at 07:40

0

You can use IsNumeric

    number = If(IsNumeric(DurationColumn), CType(DurationColumn, Integer), 0)

edited Nov 13 '12 at 07:40

Echilon

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answered Feb 25 '11 at 17:39

Fredou

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That won't work. According to http://msdn.microsoft.com/en-us/library/6cd3f6w1.aspx, "IsNumeric will also return True if the string being checked is a number containing a comma or a dollar sign". It also returns True if it's a floating-point number or a number that's larger than will fit into an integer (i.e. a Long or ULong). – Jim Mischel Feb 25 '11 at 18:20
@Jim Mischel, issue described is check for "", not for overflow or something else. I understand your point but this snippet of code does actually work – Fredou Feb 25 '11 at 18:55

score 0 · Answer 4 · answered Feb 26 '11 at 05:04

0

You could assign function return to variable first then check variable before conversion.

    Dim sRet As String = Item(DurationColumn)
    If Not String.IsNullOrEmpty(sRet) Then Convert.ToInt32(sRet)

answered Feb 26 '11 at 05:04

dev93

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CType and Type casting Exception

4 Answers4