Question

Was doing some benchmarking with IsNumeric today and compared it to the following function:

Private Function IsNumeric(ByVal str As String) As Boolean     If String.IsNullOrEmpty(Str) Then Return False     Dim c As Char      For i As Integer = 0 To Str.Length - 1         c = Str(i)         If Not Char.IsNumber(c) Then Return False     Next      Return True End Function 

I was pretty surprised with the result. With a numeric value this one was about 8-10 times faster then regular IsNumeric(), and with an empty or non-numeric value it was 1000-1500 times faster.

What is taking IsNumeric so long? Is there something else going on under the hood that I should consider before replacing it with the function above? I use IsNumeric in about 50 different places all over my site, mostly for validation of forms and query strings.

Answer 1

Where is your check for locale-specific delimiters and decimal places? Negation? Exponential notation?

You see, your function is only a tiny subset of what numeric strings can be.

1,000,000.00 1,5E59 -123456789 

You’re missing all of these.