Is it possible to validate an entry using a validator if the inputted account number exists on the database?
No, I do not. Just google Extending custom validation control. it does not even have to be that, you can just build a custom solution for that that just calls a function or something
No, you will need to write your own custom validation control
Do you have a site, that teaches on how to create a custom validation control?
Here is a simple example on validation.
Custom Data Validation to find out if the text is longer then 8 characters:
protected void TextValidate(object source, ServerValidateEventArgs args)
{
args.IsValid = (args.Value.Length >= 8);
}
Here is the Custom Validater control on the .aspx page to validate the TextBox1 control…
asp:textbox id=TextBox1 runat="server"></asp:textbox>
<asp:CustomValidator id="CustomValidator1" runat="server"
OnServerValidate="TextValidate"
ControlToValidate="TextBox1"
ErrorMessage="Text must be 8 or more characters.">
</asp:CustomValidator>
If, you want the best of both-worlds, you can also validate on the client-side…
<SCRIPT LANGUAGE="JavaScript">
function validateLength(oSrc, args){
args.IsValid = (args.Value.length >= 8);
}
</SCRIPT>
<asp:Textbox id="text1" runat="server" text="">
</asp:Textbox>
<asp:CustomValidator id="CustomValidator1" runat=server
ControlToValidate = "text1"
ErrorMessage = "You must enter at least 8 characters!"
ClientValidationFunction="validateLength" >
</asp:CustomValidator>