CustomValidator not working - asp.net

Question

I have a CustomValidator that checks if text entered in textboxes matches certain fields in a database. This was all working great before, but I have modified my page quite a bit since then and it is no longer working. I didn't think I changed anything that would affect this, but apparently I did. All my other validators (required field validators) are working correctly, but my CustomValidator isn't responding.
So anyway, here is my code:
CustomValidator:
<asp:CustomValidator ID="CustomValidator1" runat="server" ControlToValidate="txtCoursePrefix" ErrorMessage="Course number is already taken."></asp:CustomValidator>
VB codebehind:
Protected Sub CustomValidator1_ServerValidate(ByVal source As Object, ByVal args As System.Web.UI.WebControls.ServerValidateEventArgs) Handles CustomValidator1.ServerValidate
'Checking for duplicate course numbers
'get values
Dim checkPrefix = txtCoursePrefix.Text
Dim checkNum = txtCourseNum.Text
'db connectivity
Dim myConn As New OleDbConnection
myConn.ConnectionString = AccessDataSource2.ConnectionString
myConn.Open()
'select records
Dim mySelect As New OleDbCommand("SELECT 1 FROM tableCourse WHERE prefix=? AND course_number=?", myConn)
mySelect.Parameters.AddWithValue("#checkPrefix", checkPrefix)
mySelect.Parameters.AddWithValue("#checkNum", checkNum)
'execute(Command)
Dim myValue = mySelect.ExecuteScalar()
'check if record exists
If myValue IsNot Nothing Then
CustomValidator1.SetFocusOnError = True
args.IsValid = False
End If
End Sub
Everything is working up until CustomValidator1.SetFocusOnError = True and args.IsValid = False. I have tested the If statement and it's working correctly, it returns true and anything else I put inside of it executes.

Answer 1

Things you should know when using customvalidators:
If you are validating using a ValidationGroup, don't forget to add it to your CustomValidator.
Set the ControlToValidate property.
A CustomValidator control never fires when the ControlToValidate control is empty unless you set ValidateEmptyText=true.
When using ClientValidationFunction="customClientValidationFunction" use the following signature:
function customClientValidationFunction(sender, arguments) {
arguments.IsValid = true; //validation goes here
}

Answer 2

You should set the property ValidateEmptyText="true" on the CustomValidator. The client and server functions will always be called in that case.
It solved the problem for me.

Answer 3

If the handler is getting called, and you're successfully setting the args.IsValid to false, then what that does is it sets Page.IsValid to false. But unfortunately, that doesn't stop the form from being sumbitted. What you need to do is check that Page.IsValid property in your code that handles your form submit, like in the submit button handler.
So in addition to the code you posted, which sounds like it is working correctly, make sure that you have something like this for your submit handler (C# example):
protected void btnSubmit_Click(object sender, EventArgs e)
{
if (!Page.IsValid)
{
// by simply returning, the error message for the CustomValidator will be displayed
return;
}
// do processing for valid form here
}

Answer 4

Use this
OnServerValidate="CustomValidator1_ServerValidate"
like an example and it will work....
<asp:CustomValidator ID="CustomValidator1" runat="server" ControlToValidate="txtCoursePrefix" ErrorMessage="Course number is already taken." OnServerValidate="CustomValidator1_ServerValidate"></asp:CustomValidator>
Gaurav Agrawal

Answer 5

First of all, put validation group on validators and the button. If that too doesnt work, put OnClientClick='CheckValidate();' and declare the function which will call page_clientvalidate method along with the parameter.. validation group. This would surely work. If that is not working put debugger in the javascript method and debug the same