[整理]用三層實現ADO.NET的寫法（二）

 1.分析功能設計數據庫

 2.搭建三層框架
  1).表示層 UI
  2).業務邏輯層 BLL
  3).數據訪問層 DAL
  4).實體類庫 Models

 3.代碼順序
  1).根據數據庫將數據庫中的每張表封裝成對應的實體類
  2).在UI中添加應用程序配置文件，將數據庫連接字符串寫在配置文件中
  3).在DAL中寫DBHelper類

   using System; using System.Collections.Generic; using System.Text; using System.Data; using System.Data.SqlClient; using System.Configuration; namespace ...DAL { class DBHelper { static string connectionString = ConfigurationManager.ConnectionStrings["connectionString"].ConnectionString; public static string ConnectionString { get { return DBHelper.connectionString; } } public static int ExecteQuery(string cmdText,CommandType cmdType,params SqlParameter[] parameters) { using (SqlConnection conn=new SqlConnection(connectionString)) { SqlCommand cmd = new SqlCommand(); cmd.CommandText = cmdText; cmd.CommandType = cmdType; cmd.Connection = conn; PrepareCommand(cmd, parameters); try { conn.Open(); return cmd.ExecuteNonQuery(); } catch (Exception ex) { throw ex; } } } public static SqlDataReader ExecuteReader(string cmdText,CommandType cmdType, SqlConnection conn, params SqlParameter[] parameters) { SqlCommand cmd = new SqlCommand(); cmd.CommandText = cmdText; cmd.CommandType = cmdType; cmd.Connection = conn; PrepareCommand(cmd, parameters); try { return cmd.ExecuteReader(); } catch (Exception ex) { throw ex; } } public static object ExecuteScalar(string cmdText, CommandType cmdType, params SqlParameter[] parameters) { using (SqlConnection conn=new SqlConnection(connectionString)) { SqlCommand cmd = new SqlCommand(cmdText, conn); cmd.CommandType = cmdType; PrepareCommand(cmd, parameters); try { conn.Open(); return cmd.ExecuteScalar(); } catch (Exception ex) { throw ex; } } } public static DataTable GetDataTable(string cmdText, CommandType cmdType, params SqlParameter[] parameters) { using (SqlConnection conn=new SqlConnection(connectionString)) { SqlCommand cmd = new SqlCommand(cmdText, conn); cmd.CommandType = cmdType; PrepareCommand(cmd, parameters); SqlDataAdapter da = new SqlDataAdapter(cmd); DataTable dt = new DataTable(); try { da.Fill(dt); return dt; } catch (Exception ex) { throw ex; } } } private static void PrepareCommand(SqlCommand cmd, params SqlParameter[] parameters) { if (parameters != null) { foreach (SqlParameter p in parameters) { cmd.Parameters.Add(p); } } } } }

   4).在DAL中對應每個實體類創建相應的數據訪問類，使用DBHelper中的方法實現數據訪問
   5).在BLL中對應每個實體類創建相應的業務邏輯類，調用DAL中對應類的方法實現業務邏輯
   6).在UI中調用BLL中的方法實現具體操作