Resricting the number of characters entered into a multiline text box

SouthendSupporter · March 2nd, 2010, 10:34 AM

I really appreciate all the help I am getting on here. And I apologise if I am asking really basic questions.

This is where I am at.
My Function on the code behind page now looks like this:

Code:

Protected Sub ValidateText10(ByVal sender As Object, ByVal args As ServerValidateEventArgs)

        Dim numOfWords As String() = args.Value.Split(New Char() {" "c})
        ' args.IsValid = args.Value.Length <= 10
        ' args.IsValid = numofwords.Length <= 10
        args.IsValid = args.Value.Length < 11

    End Sub

The Validation now shows the Message Box correctly but if I enter anything in the text box it seems happy no matter what the length. I've tried several 'tests' as you can see but no matter how many characters I enter it does not complain.
I have not entered a MaxLength in the asp:ttextbox as I guess this would prevent the validation anyway by simply limiting the number of characters?

Lee Dumond · March 2nd, 2010, 11:04 AM

Exactly what is it you're trying to do -- limit the number of characters, or the number of words? You are not being very clear on that.

SouthendSupporter · March 2nd, 2010, 11:20 AM

Sorry --
I'm looking to limit the number of characters. I confused the issue by not checking some code I found that converted chars to words :(

timeware · March 2nd, 2010, 11:30 AM

Do you want to count the number of characters as you type or when you submit?

SouthendSupporter · March 2nd, 2010, 11:35 AM

As I type would be a great bonus!
When I submit would be better than I have now!

Lee Dumond · March 2nd, 2010, 11:39 AM

Then just use this as the method:

Code:

Protected Sub ValidateText10(ByVal source As Object, ByVal args As System.Web.UI.WebControls.ServerValidateEventArgs)      
   args.IsValid = args.Value.Length <= 10
End Sub

Here is a full example with one textbox. Just slap the same CustomValidator on every textbox you want to apply this validation method to.

Code:

<%@ Page Language="VB" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
   Protected Sub ValidateText10(ByVal source As Object, ByVal args As System.Web.UI.WebControls.ServerValidateEventArgs)
      args.IsValid = args.Value.Length <= 10
   End Sub
</script>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
   <title>Custom Validator Sample</title>
</head>
<body>
   <form id="form1" runat="server">
      <p>
         <asp:TextBox ID="TextBox1" runat="server" TextMode="MultiLine" />
         <asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" ErrorMessage="Business description is required."
            ControlToValidate="TextBox1" Display="Dynamic" />
         <asp:CustomValidator ID="CustomValidator1" runat="server" ErrorMessage="Business description too long."
            ControlToValidate="TextBox1" OnServerValidate="ValidateText10" Display="Dynamic" />
      </p>
      <asp:Button ID="btnSubmit" runat="server" Text="Submit" />
   </form>
</body>
</html>

SouthendSupporter · March 2nd, 2010, 12:31 PM

OK -- thanks for that.
I've implemented it and the validation works. That is, when I submit the page The error appears as a 'summary' rather than in the messsage box.
Presumably, this is because I am doing the validation on the server.
Is there any reason why I am -- other than my misleading everyone as a result of the example I found?
Presumably all my other validations (required field, phone format etc) are client side.
And what does display=dynamic do? I don't see any difference in behaviour whether I set Display to static,dynamic or not at all!

Lee Dumond · March 2nd, 2010, 12:41 PM

The built in controls (like RequiredField) do the validation BOTH on the server and the client. When you use a CustomValidator, there is no "built-in" validation -- you have to write it yourself. You can write server-side validation, client-side validation, or both.

When using a CustomValidator, having a server-side validation function is a MUST. That is because client-side validation, while faster for the user, is very easy to defeat.

Now that you have the server-side working, you can add the client-side validation using JavaScript.