谁能帮我注解一下DBHelper每一句是什么意思？急！！！

Question

namespace Mode.DAL
{
    public static class DBHelper
    {        private static SqlConnection connection;
        public static SqlConnection Connection
        {
            get 
            {
                string connectionString = ConfigurationManager.ConnectionStrings   ["MyBookShop"].ConnectionString;
                if (connection == null)
                {
                    connection = new SqlConnection(connectionString);
                    connection.Open();
                }
                else if (connection!=null)
                {
                    if(connection.State!= ConnectionState.Closed){
                        connection.Close();
                        connection.Open();
                    }
                }
                else if (connection.State == System.Data.ConnectionState.Broken)
                {
                    connection.Close();
                    connection.Open();
                }
                return connection;
            }
        }
        public static int ExecuteCommand(string safeSql)
        {
            SqlCommand cmd = new SqlCommand(safeSql, Connection);
            int result = cmd.ExecuteNonQuery();
            return result;
        }        public static int ExecuteCommand(string sql, params SqlParameter[] values)
        {
            SqlCommand cmd = new SqlCommand(sql, Connection);
            cmd.Parameters.AddRange(values);
            return cmd.ExecuteNonQuery();
        }        public static int GetScalar(string safeSql)
        {
            SqlCommand cmd = new SqlCommand(safeSql, Connection);
            int result = Convert.ToInt32(cmd.ExecuteScalar());
            return result;
        }        public static int GetScalar(string sql,params SqlParameter[] values)
        {
            SqlCommand cmd = new SqlCommand(sql, Connection);
            cmd.Parameters.AddRange(values);
            int result = Convert.ToInt32(cmd.ExecuteScalar());
            return result;
        }
        public static int GetScalar(string sql,CommandType type, params SqlParameter[] values)
        {
            SqlCommand cmd = new SqlCommand(sql, Connection);
            cmd.CommandType = type;
            cmd.Parameters.AddRange(values);
            int result = Convert.ToInt32(cmd.ExecuteScalar());
            return result;
        }
        public static SqlDataReader GetReader(string safeSql)
        {
            SqlCommand cmd = new SqlCommand(safeSql, Connection);
            SqlDataReader reader = cmd.ExecuteReader();
            return reader;
        }        public static SqlDataReader GetReader(string sql, params SqlParameter[] values)
        {
            SqlCommand cmd = new SqlCommand(sql, Connection);
            cmd.Parameters.AddRange(values);
            SqlDataReader reader = cmd.ExecuteReader();
            return reader;
        }
        public static SqlDataReader GetReader(string sql,CommandType type ,params SqlParameter[] values)
        {
            SqlCommand cmd = new SqlCommand(sql, Connection);
            cmd.CommandType = type;
            cmd.Parameters.AddRange(values);
            SqlDataReader reader = cmd.ExecuteReader();
            return reader;
        }
        public static DataTable GetDataSet(string safeSql)
        {
            DataSet ds = new DataSet();
            SqlCommand cmd = new SqlCommand(safeSql, Connection);
            SqlDataAdapter da = new SqlDataAdapter(cmd);
            da.Fill(ds);
            return ds.Tables[0];
        }        public static DataTable GetDataSet(string sql, params SqlParameter[] values)
        {
            DataSet ds = new DataSet();
            SqlCommand cmd = new SqlCommand(sql, Connection);
            cmd.Parameters.AddRange(values);
            SqlDataAdapter da = new SqlDataAdapter(cmd);
            da.Fill(ds);
            return ds.Tables[0];
        }    }
}

Answer 1

你可以参考这个里面的，都差不多
http://blog.csdn.net/LCL_data/archive/2009/07/19/4361258.aspx

Answer 2

using System;
using System.Collections.Generic;
using System.Text;
using System.Configuration;
using System.Data;
using System.Data.SqlClient;
using System.Web;
//using System.Web.Security;namespace Magitek.DAL
{
    /// <summary>
    /// 数据访问公共类
    /// </summary>
    public class DBHelper
    {
        private SqlConnection connection; //数据库连接        /// <summary>
        /// 不带参数初始化 DBHelper 类的新实例。
        /// </summary>
        public DBHelper()
        {          
        }        /// <summary>
        /// 打开一个数据库连接。
        /// </summary>
        private void OpenConnection()
        {
            string connectionString = "";
            try
            {
                connectionString = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;
                if (connection == null)
                {
                    connection = new SqlConnection(connectionString);
                    connection.Open();
                }
                else if (connection.State == System.Data.ConnectionState.Closed)
                {
                    connection.Open();
                }
                else if (connection.State == System.Data.ConnectionState.Broken)
                {
                    connection.Close();
                    connection.Open();
                }
            }
            catch(Exception ex)
            {
                throw new ApplicationException("数据库连接失败！\n"+ex.Message+"\n"+connectionString);
            }
        }        /// <summary>
        /// 关闭数据库连接。
        /// </summary>
        private void CloseConnection()
        {
            if (connection != null)
            {
                connection.Close();
            }
        }        /// <summary>
        /// 对连接执行 T-SQL语句并返回受影响的行数。
        /// </summary>
        /// <param name="safeSql">T-SQL语句</param>
        /// <returns></returns>
        public int ExecuteCommand(string safeSql)
        {
            OpenConnection();
            SqlCommand cmd = new SqlCommand(safeSql, connection);
            int result = cmd.ExecuteNonQuery();
            CloseConnection();
            return result;
        }        /// <summary>
        /// 对连接执行 T-SQL语句并返回受影响的行数。
        /// </summary>
        /// <param name="safeSql">T-SQL语句</param>
        /// <param name="values">SqlParameter参数</param>
        /// <returns></returns>
        public int ExecuteCommand(string sql, params SqlParameter[] values)
        {
            try
            {
                OpenConnection();
                SqlCommand cmd = new SqlCommand(sql, connection);
                cmd.Parameters.AddRange(values);
                return cmd.ExecuteNonQuery();
            }
            finally
            {
                CloseConnection();
            }
        }        /// <summary>
        /// 执行查询，并返回查询所返回的结果集中的第一行第一列。忽略其他行或列。
        /// </summary>
        /// <param name="safeSql">T-SQL语句</param>
        /// <returns></returns>
        public int GetScalar(string safeSql)
        {
            try
            {
                OpenConnection();
                SqlCommand cmd = new SqlCommand(safeSql, connection);
                int result = Convert.ToInt32(cmd.ExecuteScalar());
                return result;
            }
            finally
            {
                CloseConnection();
            }
        }        /// <summary>
        /// 执行查询，并返回查询所返回的结果集中的第一行第一列。忽略其他行或列。
        /// </summary>
        /// <param name="safeSql">T-SQL语句</param>
        /// <param name="values">SqlParameter参数</param>
        /// <returns></returns>
        public int GetScalar(string sql, params SqlParameter[] values)
        {
            try
            {
                OpenConnection();
                SqlCommand cmd = new SqlCommand(sql, connection);
                cmd.Parameters.AddRange(values);
                int result = Convert.ToInt32(cmd.ExecuteScalar());
                return result;
            }
            finally
            {
                CloseConnection();
            }
        }        /// <summary>
        /// 查询并获取一个SqlDataReader对象。
        /// </summary>
        /// <param name="safeSql">T-SQL语句</param>
        /// <returns></returns>
        public SqlDataReader GetReader(string safeSql)
        {
            OpenConnection();
            SqlCommand cmd = new SqlCommand(safeSql, connection);
            SqlDataReader reader = cmd.ExecuteReader();
            return reader;
        }        /// <summary>
        /// 查询并获取一个SqlDataReader对象。
        /// </summary>
        /// <param name="sql">T-SQL语句</param>
        /// <param name="values">SqlParameter参数</param>
        /// <returns></returns>
        public SqlDataReader GetReader(string sql, params SqlParameter[] values)
        {
            OpenConnection();
            SqlCommand cmd = new SqlCommand(sql, connection);
            cmd.Parameters.AddRange(values);
            SqlDataReader reader = cmd.ExecuteReader();
            return reader;
        }        /// <summary>
        /// 查询并获取一个DataTable对象。
        /// </summary>
        /// <param name="safeSql">T-SQL语句</param>
        /// <returns></returns>
        public DataTable GetDataTable(string safeSql)
        {
            try
            {
                OpenConnection();
                DataSet ds = new DataSet();
                SqlCommand cmd = new SqlCommand(safeSql, connection);
                SqlDataAdapter da = new SqlDataAdapter(cmd);
                da.Fill(ds);
                return ds.Tables[0];
            }
            finally
            {
                CloseConnection();
            }
        }
       
        /// <summary>
        /// 查询并获取一个DataTable对象。
        /// </summary>
        /// <param name="sql">T-SQL语句</param>
        /// <param name="values">SqlParameter参数</param>
        /// <returns></returns>
        public DataTable GetDataTable(string sql, params SqlParameter[] values)
        {
            try
            {
                OpenConnection();
                DataSet ds = new DataSet();
                SqlCommand cmd = new SqlCommand(sql, connection);
                cmd.Parameters.AddRange(values);
                SqlDataAdapter da = new SqlDataAdapter(cmd);
                da.Fill(ds);
                return ds.Tables[0];
            }
            finally
            {
                CloseConnection();
            }
        }        /// <summary>
        /// 查询并返回一个结果集对象。
        /// </summary>
        /// <param name="sql">T-SQL语句</param>
        /// <returns></returns>
        public DataSet GetDataSet(string sql)
        {
            try
            {
                OpenConnection();
                DataSet ds = new DataSet();
                SqlCommand cmd = new SqlCommand(sql, connection);
                SqlDataAdapter da = new SqlDataAdapter(cmd);
                da.Fill(ds);
                return ds;
            }
            finally
            {
                CloseConnection();
            }
        }        /// <summary>
        /// 查询并返回一个结果集对象。
        /// </summary>
        /// <param name="sql">T-SQL语句</param>
        /// <param name="values">SqlParameter参数</param>
        /// <returns></returns>
        public DataSet GetDataSet(string sql, params SqlParameter[] values)
        {
            try
            {
                OpenConnection();
                DataSet ds = new DataSet();
                SqlCommand cmd = new SqlCommand(sql, connection);
                cmd.Parameters.AddRange(values);
                SqlDataAdapter da = new SqlDataAdapter(cmd);
                da.Fill(ds);
                return ds;
            }
            finally
            {
                CloseConnection();
            }
        }        //public static string S2MD5(string str)
        //{
        //    return System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(str, "MD5");
        //}
    }
}

Answer 3

lz
这里面的问题很多，不是几行注释就能明白的，希望lz认识的学习一下，会有好处的，不懂的可以直接来问我

Answer 4

namespace Mode.DAL //命名空间
{
    public static class DBHelper
    {        private static SqlConnection connection; //申明一个静态的连接对象
        public static SqlConnection Connection //属性
        {
            get
            {
                string connectionString = ConfigurationManager.ConnectionStrings["MyBookShop"].ConnectionString;//从配置文件中读连接字符串
                if (connection == null)//如果连接为空
                {
                    connection = new SqlConnection(connectionString);//创建一个新的连接对象(连接字符串)
                    connection.Open();//打开连接
                }
                else if (connection != null)//如果连接不为空
                {
                    if (connection.State != ConnectionState.Closed)//判断当前连接是否没有关闭
                    {
                        connection.Close();//关闭连接
                        connection.Open();//打开连接
                    }
                }
                else if (connection.State == System.Data.ConnectionState.Broken)//判断是否与数据库中断
                {
                    connection.Close();//关闭连接
                    connection.Open();//打开连接
                }
                return connection;//返回连接
            }
        }
        public static int ExecuteCommand(string safeSql)//执行一条sql 语句，返回结果
        {
            SqlCommand cmd = new SqlCommand(safeSql, Connection);//创建command对象，（sql语句，连接对象）
            int result = cmd.ExecuteNonQuery();//执行语句，并用一个int来接收是否执行成功 result>0为成功，否则为失败
            return result;//返回结果
        }        public static int ExecuteCommand(string sql, params SqlParameter[] values)//重载方法。。
        {
            SqlCommand cmd = new SqlCommand(sql, Connection);//创建command对象，（sql语句，连接对象））
            cmd.Parameters.AddRange(values);//添加参数
            return cmd.ExecuteNonQuery();//返回结果
        }        public static int GetScalar(string safeSql)//执行一条sql语句返回第1行第1列的结果
        {
            SqlCommand cmd = new SqlCommand(safeSql, Connection);//创建command对象，（sql语句，连接对象）
            int result = Convert.ToInt32(cmd.ExecuteScalar());
            return result;//返回结果
        }        public static int GetScalar(string sql, params SqlParameter[] values)//执行一条sql语句返回第1行第1列的结果
        {
            SqlCommand cmd = new SqlCommand(sql, Connection);//创建command对象，（sql语句，连接对象）
            cmd.Parameters.AddRange(values);//添加参数
            int result = Convert.ToInt32(cmd.ExecuteScalar());//得到结果
            return result;//返回结果
        }
        public static int GetScalar(string sql, CommandType type, params SqlParameter[] values)//这个基本和上面一样``只是重载传入的参数不同
        {
            SqlCommand cmd = new SqlCommand(sql, Connection);
            cmd.CommandType = type;
            cmd.Parameters.AddRange(values);
            int result = Convert.ToInt32(cmd.ExecuteScalar());
            return result;
        }
        public static SqlDataReader GetReader(string safeSql)//返回一个reader结果集
        {
            SqlCommand cmd = new SqlCommand(safeSql, Connection);//创建command对象，（sql语句，连接对象）
            SqlDataReader reader = cmd.ExecuteReader();//执行sqlDateRead方法
            return reader;//返回结果集
        }        public static SqlDataReader GetReader(string sql, params SqlParameter[] values)//重载，和上面一样，多传了一个参数数组进来
        {
            SqlCommand cmd = new SqlCommand(sql, Connection);
            cmd.Parameters.AddRange(values);
            SqlDataReader reader = cmd.ExecuteReader();
            return reader;
        }
        public static SqlDataReader GetReader(string sql, CommandType type, params SqlParameter[] values)//重载，和上面一样，多传一个CommandType进来...
        {
            SqlCommand cmd = new SqlCommand(sql, Connection);
            cmd.CommandType = type;
            cmd.Parameters.AddRange(values);
            SqlDataReader reader = cmd.ExecuteReader();
            return reader;
        }
        public static DataTable GetDataSet(string safeSql)//返回一个表...
        {
            DataSet ds = new DataSet();
            SqlCommand cmd = new SqlCommand(safeSql, Connection);
            SqlDataAdapter da = new SqlDataAdapter(cmd);
            da.Fill(ds);
            return ds.Tables[0];
        }        public static DataTable GetDataSet(string sql, params SqlParameter[] values)//还是返回一个表。重载，带参数的
        {
            DataSet ds = new DataSet();
            SqlCommand cmd = new SqlCommand(sql, Connection);
            cmd.Parameters.AddRange(values);
            SqlDataAdapter da = new SqlDataAdapter(cmd);
            da.Fill(ds);
            return ds.Tables[0];
        }    }
}分不给我那我哭死