R – ASP/VBScript “Gotchas”

• Int()

The Int function returns the integer part of a specified number.

• CInt()

The CInt function converts an expression to type Integer.

And the best answer comes from MSDN

CInt differs from the Fix and Int functions, which truncate, rather than round, the fractional part of a number. When the fractional part is exactly 0.5, the CInt function always rounds it to the nearest even number. For example, 0.5 rounds to 0, and 1.5 rounds to 2.

You have a couple of choices. You can be proactive by checking ahead of time whether the value is numeric using the IsNumeric function:

 If IsNumeric(trainCostStr) Then
    totalTrainCost = totalTrainCost + CInt(trainCostStr)
 Else
    ' Do something appropriate
 End If

...or you can be reactive by using error catching; in Classic ASP probably easiest to define a function and use On Error Resume Next:

Function ConvertToInt(val)
    On Error Resume Next
    ConvertToInt = CInt(val)
    If Err.Number <> 0 Then
        ConvertToInt = Empty
        Err.Clear
    End If
End Function

Or return 0 or Null or whatever suits you, then use it in your trainCost code.

Note that CInt expects an integer and will stop at the first non-digit, so "123.45" comes back as 123. Look at the other conversions, CDouble, CCur, etc.