systems.cs

《C#和.NET第一步》中的财务系统 利用三层结构做的

using System;
using System.Collections.Generic;
using System.Text;
using System.Data.SqlClient;
using System.Data;
namespace DataAccess
{
	public class Systems
	{
		private readonly string connection = "server=.;database=homemoney;uid=sa;pwd=";
		private readonly string tablename = "T_System";
		private SqlConnection cn = null;
		private SqlDataAdapter dataAdapter = null;
		private SqlConnection Connection
		{
			get
			{
				if (cn == null || cn.State == ConnectionState.Closed)
					cn = new SqlConnection(connection);
				return cn;
			}
		}
		public DataSet GetSysItems()
		{
			//要返回的数据集
			DataSet ds = new DataSet();
			//构造插入数据的SQL语句
			string sql = "SELECT * FROM T_System";
			if (dataAdapter == null) dataAdapter = new SqlDataAdapter(sql, connection);
			try
			{
				dataAdapter.Fill(ds, this.tablename);
			}
			catch (SqlException e)
			{
				Common.Logger.Log(e.Message);
			}
			return ds;
		}
	}
}