C#DBHelper的简单使用

1.在App.config中的<configuration></configuration>加入连接串 例： 第一种方法

  <connectionStrings>
    <add name="con" connectionString="server=.;database=数据库名称;uid=sa;pwd=sa"/>
  </connectionStrings>

列：第二种方法的连接串直接在DBHelper类中写入连接串

  private readonly string sqlcon = "server=.;database=数据库名称;uid=sa;pwd=sa;";

2.在DBHelper中写入

//第一种
private static SqlConnection Con
        {
            get
            {
                var con = new SqlConnection(ConfigurationManager.ConnectionStrings["con"].ConnectionString);
                con.Open();
                return con;
            }
        }
//第二种  都可以用
 public SqlConnection sqlCon()
        {
            SqlConnection sql = new SqlConnection(sqlcon);
            sql.Open();
            return sql;
        }
        private static SqlCommand Cmd
        {
            get
            {
                return new SqlCommand { Connection = Con };
            }
        }
        /// <summary>
        /// 增删改
        /// </summary>
        /// <param name="sql"></param>
        /// <returns></returns>
        public static bool Update(string sql)
        {
            var cmd = Cmd;
            cmd.CommandText = sql;
            try
            {
                return cmd.ExecuteNonQuery() > 0;
            }
            finally
            {
                cmd.Connection.Close();
            }
        }
        /// <summary>
        /// 获取一个对象
        /// </summary>
        /// <param name="sql"></param>
        /// <returns></returns>
        public static object SelectForScalar(string sql)
        {
            var cmd = Cmd;
            cmd.CommandText = sql;
            try
            {
                return cmd.ExecuteScalar();
            }
            finally
            {
                cmd.Connection.Close();
            }
        }
        /// <summary>
        /// 获取一个结果集
        /// </summary>
        /// <param name="sql"></param>
        /// <returns></returns>
        public static SqlDataReader SelectForReader(string sql)
        {
            var cmd = Cmd;
            cmd.CommandText = sql;
            try
            {
                return cmd.ExecuteReader(CommandBehavior.CloseConnection);
            }
            catch
            {
                cmd.Connection.Close();
                throw;
            }
        }

以上就是把dbhelper帮助工具类写好了

3.例如对数据库某个表进行增删改查的话  例：对一个Class班级表进行操作演示

　　3.1先创建一个对应数据库的实体表

　　　　

  　　   /// <summary>
        /// 编号
        /// </summary>
        public int Id { get; set; }
        /// <summary>
        /// 班级名称
        /// </summary>
        public string ClassName { get; set; }

　　3.2写这个表对应的增删改查

　　

 /// <summary>
        /// 添加班级
        /// </summary>
        /// <param name="cls"></param>
        /// <returns></returns>
        public bool CreateClass(Models.Class cls)
        {
            return DBHelper.Update($"insert into Classes values('{cls.ClassName}','false',getdate())");
        }
        /// <summary>
        /// 修改班级
        /// </summary>
        /// <param name="cls"></param>
        /// <returns></returns>
        public bool EditClass(Models.Class cls)
        {
            return DBHelper.Update($"update Classes set Name='{cls.ClassName}' where Id='{cls.Id}'");
        }
        /// <summary>
        /// 删除班级
        /// </summary>
        /// <param name="cls"></param>
        /// <returns></returns>
        public bool RemoveClass(Models.Class cls)
        {
            return DBHelper.Update($"update Classes set IsRemove='true' where Id='{cls.Id}'");
        }
        /// <summary>
        /// 获取一个班级信息
        /// </summary>
        /// <returns></returns>
        public Models.Class GetOneClasses(string className)
        {
            var dr = DBHelper.SelectForReader($"select Id,Name from Classes where Name='{className}'");
            Models.Class classes = null;
            if (dr.Read())
            {
                classes=new Models.Class()
                {
                    Id = dr.GetInt32(0),
                    ClassName = dr.GetString(1),
                };
            }
            dr.Close();
            return classes;
        }
        /// <summary>
        /// 获取所有班级信息
        /// </summary>
        /// <returns></returns>
        public List<Models.Class> GetAllClasses()
        {
            var dr = DBHelper.SelectForReader("select Id,Name from Classes");
            List<Models.Class> classes = new List<Models.Class>();
            while (dr.Read())
            {
                classes.Add(new Models.Class()
                {
                    Id = dr.GetInt32(0),
                    ClassName=dr.GetString(1),
                });
            }
            dr.Close();
            return classes;
        }

4.调用写好的增删改班级的语句

 ClassService classSvc  = new  ClassService();  //这是你写Class增删改的类 实例化过来 

        /// <summary>
        /// 添加班级
        /// </summary>
        /// <param name="name"></param>
        /// <param name="bornDate"></param>
        /// <param name="classId"></param>
        /// <returns></returns>
        public bool CreateClass(string name)
        {
            if (string.IsNullOrEmpty(name))
            {
                throw new Exception("请输入班级姓名！");
            }
            return classSvc.CreateClass(new Models.Class() { ClassName = name });
        }

4.控制台直接调

//把3.类初始化到控制台
//列 Classes cls =new Classes()
cls.CreateClass("一年级");
//OK了