A very annoying error

I am writting my first web application in c#.
I have a couple of error that I can't solve it.
The first one (and the most annoying):

Description: An error occurred during the parsing of a resource required to service this request. Please review the following specific parse error details and modify your source file appropriately.

Parser Error Message: Could not load type '_8_1.FinalFilter'.

Line 1: <%@ Page language="c#" Codebehind="FinalFilter.aspx.cs" AutoEventWireup="false" Inherits="_8_1.FinalFilter" %>

where I'm going wrong here?

The second one:

Exception Details: System.Data.OleDb.OleDbException: No value given for one or more required parameters.