网上购物系统（Task003）——通用数据库访问函数集SqlHelper类

六、代码页中的类SQLHelper

[csharp] using System;
using System.Data;
using System.Data.SqlClient;
using System.Configuration;
using System.Collections.Generic;
using WestGarden.Model;

namespace WestGarden.Web
{
    public partial class Default6 : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            IList<CategoryInfo> catogories = new List<CategoryInfo>();

            string connectionString = ConfigurationManager.ConnectionStrings["NetShopConnString"].ConnectionString;
            string cmdText = "SELECT * FROM Category";

            //使用静态类，可直接调用，不需要new。
            SqlDataReader rdr = SqlHelper.ExecuteReader(connectionString, CommandType.Text, cmdText,null);

            while (rdr.Read())
            {
                CategoryInfo category = new CategoryInfo(rdr.GetString(0), rdr.GetString(1), rdr.GetString(2));
                catogories.Add(category);
            }
            rdr.Close();

            repCategories.DataSource = catogories;
            repCategories.DataBind();
        }
    }

    //这个类是静态的，应用程序启动时，自动驻留在内存中，所建连接，在使用过程中，
    //也只是Close()，放回到连接池中。并没有注销Dispose()，可以下次连接时，快速使用。
    public abstract class SqlHelper
    {
        public static SqlDataReader ExecuteReader(string connectionString, CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
        {
            SqlCommand cmd = new SqlCommand();
            SqlConnection conn = new SqlConnection(connectionString);

            try
            {
                //cmd.Connection = conn;
                //cmd.CommandType = cmdType;
                //cmd.CommandText = cmdText;

                //conn.Open();

                PrepareCommand(cmd, conn, null, cmdType, cmdText, commandParameters);

                //如果创建了 SqlDataReader 并将 CommandBehavior 设置为 CloseConnection，
                //则关闭 SqlDataReader 会自动关闭此连接。
                SqlDataReader rdr = cmd.ExecuteReader(CommandBehavior.CloseConnection);
                cmd.Parameters.Clear();
                return rdr;
            }
            catch
            {
                conn.Close();
                throw;
            }
            //finally
            //{
            //    conn.Close();
            //}
        }

        private static void PrepareCommand(SqlCommand cmd, SqlConnection conn, SqlTransaction trans, CommandType cmdType, string cmdText, SqlParameter[] cmdParms)
        {

            if (conn.State != ConnectionState.Open)
                conn.Open();

            cmd.Connection = conn;
            cmd.CommandText = cmdText;

            if (trans != null)
                cmd.Transaction = trans;

            cmd.CommandType = cmdType;

            if (cmdParms != null)
            {
                foreach (SqlParameter parm in cmdParms)
                    cmd.Parameters.Add(parm);
            }
        }
    }
}
using System;
using System.Data;
using System.Data.SqlClient;
using System.Configuration;
using System.Collections.Generic;
using

补充：Web开发 , ASP.Net ,