C# 增删改查应用（三）

ADO.NET技术,该技术用于.net程序操作数据库

ADO的组成:

1.数据提供程序

    a.Connection:连接对象,用于指定数据库服务器的相关信息(数据库服务名 数据库用户名  密码等)

    b.Command:命令对象,用于对数据库执行增删改查的操作,会提供对应的操作方法

2.数据集

   对数据库的操作:

      1.导名称空间System.Data.SqlClient (用于连接Sql server数据库)

      2.创建连接对象
           //连接字符串的格式: server=数据库服务名;database=数据库;uid=用户名;pwd=密码
            String conStr = "server=192.168.0.102;database=MySchool3;uid=sa;pwd=sa";
            SqlConnection cn = new SqlConnection(conStr);

      3.打开连接
            cn.open();

      4.创建命令对象
           String sql = "delete student where studentId="+this.textBox1.Text;
           SqlCommand cmd = new SqlCommand(sql,con);

       5.执行命令对象
           int count=cmd.ExecuteNonQuery();//该方法的返回值:sql语句执行后  受影响的行数
           ExecuteNonQuery方法用于执行增删改

       6.关闭连接对象
           cn.close();

SqlHelper类：

  /// <summary>
    /// 数据库操作通用类
    /// 达到了sql防注入，并且，将对数据库的操作独立开来，可以提高内聚，降低耦合。达到了哪里使用，哪里关闭的效果，避免隐患。
    /// </summary>
    public class SqlHelper
    {
        SqlConnection conn = null;
        SqlCommand com = null;
        SqlDataReader rd = null;
        string constr = System.Configuration.ConfigurationManager.ConnectionStrings["Family"].ToString();

        /// <summary>
        /// 打开数据库连接
        /// </summary>
        /// <returns></returns>
        public bool ConnectSql()
        {
            try
            {
                conn = new SqlConnection(constr);
                conn.Open();
                return true;
            }
            catch
            {
                return false;
            }
        }

        /// <summary>
        /// 关闭数据库连接
        /// </summary>
        public void closeConn()
        {
            try
            {
                if (conn != null) { conn.Close(); }
                if (rd != null) { rd.Close(); }
            }
            catch
            {
                return;
            }

        }

        /// <summary>
        /// 数据增删改
        /// </summary>
        /// <param name="sql">sql语句</param>
        /// <param name="dic">数据集合对象</param>
        /// <returns></returns>
        public static bool SqlPour(string sql, Dictionary<string, string> dic)
        {
            try
            {
                ConnectSql();
                com = new SqlCommand(sql, conn);
                if (dic != null)
                {
                    foreach (var item in dic)
                    {
                        com.Parameters.AddWithValue(item.Key, item.Value);
                    }
                }
                com.ExecuteNonQuery();
                return true;
            }
            catch (Exception e)
            {
                Console.WriteLine(e.Message);
                return false;
            }
            finally
            {
                closeConn();
            }
        }

        /// <summary>
        /// 查询数据返回ArrayList
        /// </summary>
        /// <param name="sql">sql语句</param>
        /// <param name="dic">数据集合对象</param>
        /// <returns></returns>
        public static ArrayList SelectInfo(string sql, Dictionary<string, string> dic)
        {  
            try
            {
                ConnectSql();   
                com = new SqlCommand(sql, conn);
                ArrayList al = new ArrayList();
                if (dic != null)
                {
                    foreach (var item in dic)
                    {   //遍历参数并进行赋值，防止sql注入
                        com.Parameters.AddWithValue(item.Key, item.Value);
                    }
                }
                rd = com.ExecuteReader();
                int clumn = 0;  //得到数据的列数
                if (rd.Read())
                {
                    clumn = rd.FieldCount;
                }
                else
                {
                    return null;
                }
                do
                {   //读取每行每列的数据并放入Object数组中
                    Object[] obj = new object[clumn];
                    for (int i = 0; i < clumn; i++)
                    {
                        obj[i] = rd[i];
                    }
                    al.Add(obj);  //将一行数据放入数组中
                } while (rd.Read());
                return al;
            }
            catch
            {
                return null;
            }
            finally
            {
                closeConn();
            }

        }
    }

调用：

        //----------------------------公共类 sqlHelper 调用------------------------------------------
        /// <summary>
        /// 根据条件查询
        /// </summary>
        /// <param name="UserID">参数</param>
        /// <param name="UserCreationtime">参数</param>
        /// <returns></returns>
        public static bool GetInfo(string UserID, DateTime UserCreationtime)
        {
            string sql = "select * from [User]  where UserID=@UserID and UserCreationtime=@UserCreationtime";
            Dictionary<string, string> dic = new Dictionary<string, string>();
            dic.Add("@UserID", UserID);
            dic.Add("@UserCreationtime", UserCreationtime.ToString());
            ArrayList al = SqlHelper.SelectInfo(sql, dic);
            //判断是否为空，空为false
            if (al.Count > 0)
            {
                //得到几行数据就能产生多少个对象
                foreach (Object[] obj in al)
                {
                    User uset = new User();
                    uset.UserID = obj[0].ToString();
                    //参数转换，强转很容易发生异常，所以数据库的约束性要强，对象类时要认真检查数据类型，多用try...catch
                    uset.UserCreationtime = Convert.ToDateTime(obj[1]);
                }
            }
            else
            {
                return false;
            }
            return true;
        }

        /// <summary>
        /// 增加数据
        /// </summary>
        /// <param name="UserleverlType">参数</param>
        /// <returns></returns>
        public static bool GetAdd(string UserlevelID, string UserleverlType)
        {
            Dictionary<string, string> dic = new Dictionary<string, string>();
            var strSql = "insert into [level] (UserlevelID, UserleverlType)values(@UserlevelID,@UserleverlType)"; //放置占位符
            dic.Add("@UserlevelID", UserlevelID);
            dic.Add("@UserleverlType", UserleverlType);    //将其放入字典（类似JSON，采用键值对的方式传递）
            if (!SqlHelper.SqlPour(strSql, dic)) { return false; }
            return true;
        }

        /// <summary>
        /// 修改数据
        /// </summary>
        /// <param name="UserName">参数</param>
        /// <param name="UserSet">参数</param>
        /// <returns></returns>
        public static bool GetUpdate(string UserName, string UserSet, string UserID)
        {
            Dictionary<string, string> dic = new Dictionary<string, string>();
            var strSql = "update [User] set UserName=@UserName, UserSet=@UserSet where UserID=@UserID";
            dic.Add("@UserID", UserID);
            dic.Add("@UserName", UserName);
            dic.Add("@UserSet", UserSet);
            dic.Add("@UserCreationtime", DateTime.Now.ToString());
            if (!SqlHelper.SqlPour(strSql, dic)) { return false; }
            return true;
        }

        /// <summary>
        /// 根据条件删除数据
        /// </summary>
        /// <param name="UserID">参数</param>
        /// <returns></returns>
        public static bool GetDel(string UserID)
        {
            Dictionary<string, string> dic = new Dictionary<string, string>();
            string sql = "DELETE FROM [User] WHERE UserID=@UserID";
            dic.Add("UserID", UserID);
            if (!SqlHelper.SqlPour(sql, dic)) { return false; }
            return true;
        }