configuration system failed to initialize entity faramework error

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C#

Visual-Studio

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hello,
i am trying to learn entity framewrok, so i go to first example, but i faced an error

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data;
using System.Data.Objects;
using System.Data.EntityClient;
using System.Data.Entity;
using System.ComponentModel;


namespace ConsoleApplication3
{
    class Program
    {
        static void Main(string[] args)
        {
            try
            {
                using (Entities ctx = new Entities())
                {
                    var OracLinq = from e in ctx.AM_GI_COUNTRIES
                                   where e.PK_CODE == 42
                                   select e;
                    Console.WriteLine("LINQ to Entites Result");

                    foreach (var result in OracLinq)
                    {
                        Console.WriteLine("COD:" + result.PK_CODE);
                    }

                    Console.WriteLine();
                    Console.ReadLine();
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message.ToString());
            }
        }
    }
}

after i added the DataModel
when the code trying to execute "using (Entities ctx = new Entities())" error happen with exception: configuration system failed to initialize
do i miss something?
i have:
windows 7 64bit
visual studio 2010
oracle cilent 12g