ADO.NET基础

已ASP.Net为例子，新建一个ASP.NET项目

1、配置Web.config文件

     连接字符串：Data Source=.;Initial Catalog=Test1;User Id=sa;Password=123456;

     DataSource：资源名称，“.”表示本地地址（127.0.0.1），有时候也会访问不到，可以填上本地电脑名称

     Initial Catalog：数据库名

     User Id：数据库用户名

     Password：数据库用户密码

2、新建一个SqlHelper.cs类

    编写之前，需要先添加System.Configuration的引用

   

public static class SqlHelper
    {
        //取连接字符串
        public static readonly string connstr = ConfigurationManager.ConnectionStrings["ConnStr"].ConnectionString;

        /// <summary>
        /// 打开连接
        /// </summary>
        /// <returns></returns>
        public static SqlConnection OpenConnection()
        {
            SqlConnection conn = new SqlConnection(connstr);
            conn.Open();
            return conn;
        }

        public static int ExecuteNonQuery(string cmdText,params SqlParameter[] parameters)
        {
            using (SqlConnection conn = new SqlConnection(connstr))
            {
                conn.Open();
                return ExecuteNonQuery(conn, cmdText, parameters);
            }
        }

        public static object ExecuteScalar(string cmdText,params SqlParameter[] parameters)
        {
            using (SqlConnection conn = new SqlConnection(connstr))
            {
                conn.Open();
                return ExecuteScalar(conn, cmdText, parameters);
            }
        }

        public static DataTable ExecuteDataTable(string cmdText,params SqlParameter[] parameters)
        {
            using (SqlConnection conn = new SqlConnection(connstr))
            {
                conn.Open();
                return ExecuteDataTable(conn,cmdText,parameters);
            }
        }  

        /// <summary>
        /// 执行语句，返回受影响的行数
        /// </summary>
        /// <param name="conn">连接</param>
        /// <param name="cmdText">sql语句</param>
        /// <param name="parameters">参数</param>
        /// <returns></returns>
        public static int ExecuteNonQuery(SqlConnection conn, string cmdText,params SqlParameter[] parameters)
        {
            using (SqlCommand cmd = conn.CreateCommand())
            {
                cmd.CommandText = cmdText;
                cmd.Parameters.AddRange(parameters);
                return cmd.ExecuteNonQuery();
            }
        }

        /// <summary>
        /// 返回查询结果的第一行第一列
        /// </summary>
        /// <param name="conn">连接</param>
        /// <param name="cmdText">sql语句</param>
        /// <param name="parameters">参数</param>
        /// <returns></returns>
        public static object ExecuteScalar(SqlConnection conn,string cmdText,params SqlParameter[] parameters)
        {
            using (SqlCommand cmd = conn.CreateCommand())
            {
                cmd.CommandText = cmdText;
                cmd.Parameters.AddRange(parameters);
                return cmd.ExecuteScalar();
            }
        }

        /// <summary>
        /// 返回查询结果集
        /// </summary>
        /// <param name="conn">连接</param>
        /// <param name="cmdText">sql语句</param>
        /// <param name="parameters">参数</param>
        /// <returns></returns>
        public static DataTable ExecuteDataTable(SqlConnection conn,string cmdText,params SqlParameter[] parameters)
        {
            using (SqlCommand cmd = conn.CreateCommand())
            {
                cmd.CommandText = cmdText;
                cmd.Parameters.AddRange(parameters);
                using (SqlDataAdapter adapter = new SqlDataAdapter(cmd) )
                {
                    DataTable table = new DataTable();
                    adapter.Fill(table);
                    return table;
                }  
            }
        }

        /// <summary>
        /// 存值到数据库NULL处理
        /// </summary>
        /// <param name="value"></param>
        /// <returns></returns>
        public static object ToDBValue(this object value)
        {
            return value == null ? DBNull.Value : value;
        }

        /// <summary>
        /// 从数据库取数据NULL处理
        /// </summary>
        /// <param name="dbValue"></param>
        /// <returns></returns>
        public static object FromDBValue(this object dbValue)
        {
            return dbValue == null ? null : dbValue;
        }
}

 

3、。。。