Cant connect to Sql Compact!

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C#

Hello

im making Win Mobile 6 pro aplication and when i click button add should add details from textbox's to database , but when i click buton im always getting same error "The path is not valid" , i try to copy to other folders my DB but result is same, i make new project and new database to try whit new project but again same ... i dont know where im wrong the code where im using is :

using System;
using System.Linq;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Data.SqlServerCe;

namespace SmartDeviceProject1
{
    public partial class novart2 : Form
    {
        public novart2()
        {
            InitializeComponent();
        }

        SqlCeConnection cn = new SqlCeConnection("Data Source=C:\\Users\\USER\\Documents\\Visual Studio 2008\\Projects\\SmartDeviceProject1\\Ege.sdf");
        SqlCeCommand cmd = new SqlCeCommand();

        private void menuItem1_Click(object sender, EventArgs e)
        {
            novart f = new novart();
            f.Show();
        }


        private void button1_Click(object sender, EventArgs e)
        {
            try
            {
                cn.Open();
                cmd = new SqlCeCommand ("Insert into Art (mr,group_id,subgroup_id,quantity_on_stock) values('"+txtmr.Text +"','"+txtgr.Text +"','"+txtsubg.Text +"','"+txtqnt.Text +"')", cn);
                cmd.ExecuteNonQuery();
                MessageBox.Show("Update Successfull to the Database");
                cn.Close();
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }

        }
    }
}