Custom Validation
Creating your own validation isn't too hard, if you're no
good a regular expressions then you can use this to do them. The following one
makes sure that your entry is at least 8 letters long.
<script language="VB" runat="server">
Sub ValidateMe(sender as object, e as ServerValidateEventArgs)
If Len(e.Value) > 8 Then
e.IsValid = True
Else
e.IsValid = False
End If
End Sub
</script>Enter a username:<asp:textbox
id="username" runat="server" /><p>
<asp:CustomValidator runat="server"
OnServerValidate="ValidateMe" ControltoValidate="username" ErrorMessage="Username
must be at least 8 letters long" /> |
Ok, the sub takes in the usual values, but it takes in
ServerValidateEventArgs instead of EventArgs, this lets you get the value and
set the IsValid Property. However this is server side validation (you'll learn
more about why this is important soon), to make it client side, just add the
property - "OnClientSideValidator="validating"".
Then add some client side JavaScript to handle it (in the form of a function),
otherwise it gets processed on the server.
But wait! There's more!
More? Yes! Here are some things that will add
you your adventure's. Now obviously, having the Error text red all the time
will get a bit annoying, so you can add the ForeColor = "Color" property to the control to change the error text
color.
Now if you take all the code that I've given
you on this page and put it into one file, add a submit button, form tags and
then run it you will see that the Validation occurs with JavaScript and Span
tags. This means that the page doesn't get submitted until the validators are
satisfied with what you've put in. But you'll also see that there are gaps
where the validators are on the page which are blank, they are activated when
an error is found. You can set a Display property to change this -
- Display = "None" 'No
error message is displayed and the spaces are gone
- Display = "Static" 'Default,
spaces are left for the errors
- Display = "Dynamic" 'Spaces are
generated only if an error occurs.
You'll learn more about this in the next
section.
When you submit the page, it doesn't go through
until the validators are happy, when it is submitted, its checked again and a
value - Page.IsValid is generated to tell you if all the validators are happy
-
<script language="VB" runat="server"
>
Sub Page_Load(sender as object, e as EventArgs)
If Page.IsPostBack Then
If Page.IsValid Then
lblMessage.Text = "You passed Validation"
End If
End If
End Sub
</script>
<asp:label id="lblMessage" runat="server"/><p> |
See?
