SqlBulkCopy Avoid duplicate inserts rows then automatically  update in  existing rows  while importing Excel File in Asp Net Mvc plz to send solution

  public ActionResult Index(HttpPostedFileBase postedFile)
        {

           
            //GridView.DataSource = ds.Tables[0];
            //GridView1.DataBind();
            string filePath = string.Empty;
            if (postedFile != null)
            {
                string path = Server.MapPath("~/Uploads/");
                if (!Directory.Exists(path))
                {
                    Directory.CreateDirectory(path);
                }

                filePath = path + Path.GetFileName(postedFile.FileName);
                string extension = Path.GetExtension(postedFile.FileName);
                postedFile.SaveAs(filePath);

                string conString = string.Empty;
                switch (extension)
                {
                    case ".xls": //Excel 97-03.
                        conString = ConfigurationManager.ConnectionStrings["Excel03ConString"].ConnectionString;
                        break;
                    case ".xlsx": //Excel 07 and above.
                        conString = ConfigurationManager.ConnectionStrings["Excel07ConString"].ConnectionString;
                        break;
                }

                DataTable dt = new DataTable();
                DataSet ds = new DataSet();
              
                conString = string.Format(conString, filePath);

                using (OleDbConnection connExcel = new OleDbConnection(conString))
                {
                    using (OleDbCommand cmdExcel = new OleDbCommand())
                    {
                        using (OleDbDataAdapter odaExcel = new OleDbDataAdapter())
                        {
                            cmdExcel.Connection = connExcel;

                            //Get the name of First Sheet.
                            connExcel.Open();
                            DataTable dtExcelSchema;
                            dtExcelSchema = connExcel.GetOleDbSchemaTable(OleDbSchemaGuid.Tables, null);
                            string sheetName = dtExcelSchema.Rows[0]["TABLE_NAME"].ToString();
                            dt.Columns.AddRange(new DataColumn[3] { new DataColumn("Id", typeof(int)),
                new DataColumn("Name", typeof(string)),
                new DataColumn("Country",typeof(string)) });
                           
                          
                         


                            connExcel.Close();

                            //Read Data from First Sheet.
                            connExcel.Open();
                            cmdExcel.CommandText = "SELECT * From [" + sheetName + "]";
                            odaExcel.SelectCommand = cmdExcel;
                            odaExcel.Fill(dt);
                          

                            connExcel.Close();
                        }
                    }
                }

                conString = ConfigurationManager.ConnectionStrings["Constring"].ConnectionString;
                using (SqlConnection con = new SqlConnection(conString))
                {
                    using (SqlCommand cmd = new SqlCommand("Update_Customers"))
                    {
                        cmd.CommandType = CommandType.StoredProcedure;
                        cmd.Connection = con;
                        cmd.Parameters.AddWithValue("@tblCustomers", dt);
                        con.Open();
                        cmd.ExecuteNonQuery();
                        con.Close();
                    }
                }
            }

            return View();
        }
    }
}