users.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;
using Common;
namespace DataAccess
{
	public class Users
	{
		private readonly string connection = "server=.;database=homemoney;uid=sa;pwd=";
		private readonly string tablename = "T_User";
		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 bool Insert(User t)
		{
			//构造插入数据的SQL语句
			string sql = string.Format("INSERT INTO T_User VALUES('{0}','{1}','备注','{2}')",
			t.UName, t.UPwd, t.UAccountName
			);
			SqlCommand cmd = new SqlCommand(sql, Connection);
			try
			{
				//插入数据库
				cmd.Connection.Open();
				cmd.ExecuteNonQuery();
			}
			catch (SqlException e)
			{
				Console.WriteLine(e.Message);
				return false;
			}
			finally
			{
				cmd.Connection.Close();
			}
			return true;
		}

		public DataSet GetUsers()
		{
			//要返回的数据集
			DataSet ds = new DataSet();
			//构造插入数据的SQL语句
            string sql = "SELECT UID,UName,UPwd,UAccountName,URemark FROM T_User";
			if (dataAdapter == null) dataAdapter = new SqlDataAdapter(sql, connection);
			try
			{
				dataAdapter.Fill(ds, this.tablename);
			}
			catch (SqlException e)
			{
				Console.WriteLine(e.Message);
			}
			return ds;
		}
	}
}