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Wouter Benoit
Starting Member

23 Posts

Posted - 2007-10-18 : 07:54:01

Im trying to create a regular expression to check if the user enters a numeric value in the text field.

I use the following code

Dim maskerbedrag As Regex = New Regex("(0-9)+[,]?(0-9)*")
Dim bedrag As Decimal
Dim M As Match = maskerbedrag.Match(bedrag)

If M.Success Then
bedrag = txtOverschrijven.Text
else
msgbox("error in value textfield")
end if

I read a document about regular expressions and as I understood it, my code should do the following

one or more numeric characters that might by followed by a comma and zero or more numeric characters.

But when, for example, I fill in 15 or 15,5 in the text field, I get the error message I coded.

How is this possible? I'm new to using regular expressions and I don't understand what went wrong.

Can someone please explain or tell me what I do wrong.

Thanks in advance

Wouter Benoit
Starting Member

23 Posts

Posted - 2007-10-18 : 08:02:46

OK, I just found one stupid mistake in my code and that is that I dont give the variable 'bedrag' a value before it is checked by the regular expression.
So the code now is

Dim maskerbedrag As Regex = New Regex("(0-9)+[,]?(0-9)*")
Dim bedrag As Decimal
bedrag = CDec(txtOverschrijven.Text)
Dim M As Match = maskerbedrag.Match(bedrag)

If M.Success Then
msgbox("Succes")
else
msgbox("error in value textfield")
end if

But it still doesn't seem to work.

jsmith8858
Dr. Cross Join

7423 Posts

Posted - 2007-10-18 : 08:36:53

All you need to do is use one of the ASP.NET validation controls on the TextBox to check to see if it is a valid numeric. Like this:

<asp:CompareValidator Runat="server" ControlToValidate="txtOverschrijven"
ErrorMessage="Must be a number!"
Type="Double" Operator="DataTypeCheck" ID="Comparevalidator1" >*</asp:CompareValidator>

Read about that in the ASP.NET help pages or google it for more info.

FYI -- What are you are trying to do doesn't making any sense. You have a string, from a text box. You are then converting that string to a decimal -- which will fail right there if the string isn't a valid number! Then, you are applying a regular expression check on the decimal, which has been implicitly converted BACK to a string. Also, you can just use the IsMatch(Value) property of the RegularExpression object to do a quick check to see if a value matches the pattern.

But overall, don't use regular expressions for this -- use validation controls. You can also simply use Decimal.Parse() in a TRY block, or use Decimal.TryParse() in .net 2.0.

For example:


Dim Dec as decimal = 0
Dim Valid as Boolean = False

Begin Try
  Dec = Decimal.Parse(txtOverschrijven.Text)
  Valid = True
Catch Ex As Exception
  Valid = False
End Try

If Valid Then
  MsgBox("Success!")
Else
  Msgbox("Error! Not Valid!")
End If

- Jeff
http://weblogs.sqlteam.com/JeffS

Wouter Benoit
Starting Member

23 Posts

Posted - 2007-10-18 : 09:18:42

That works just fine.
Thanks a lot Jeff

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