实体类在Windows程序中的高级应用--------------------》》心境是一种境界。

string str = "data source=.;initial catalog=MySchool;uid=sa;pwd=1";
            SqlConnection con = new SqlConnection(str);
            string sql = "insert into grade values(@gname)";
            SqlParameter para = new SqlParameter("@gname", txtName.Text);
            SqlCommand cmd = new SqlCommand(sql, con);
            //1.0  必须在连接打开之后，用连接对象con.beginTransaction
            SqlTransaction tran = con.BeginTransaction();
            cmd.Parameters.Add(para);
            con.Open();
            //1.1   将通过con构建出的事务对象和  cmd的Transaction属性绑定
            cmd.Transaction = tran;
                //初始值要给
                    int count = 0;
            try
            {
                count = cmd.ExecuteNonQuery();
                //1.3 提交事务
                tran.Commit();
            }
            catch (Exception ex)
            {
                //1.4回滚事务
                tran.Rollback();
                MessageBox.Show(ex.Message);
            }
            if (count > 0)
            {
                MessageBox.Show("添加成功！");
            }
            con.Close();

select * from Grade with(nolock)

using System;
using System.Collections.Generic;
using System.Text;
using System.Windows.Forms;

/// <summary>
/// 消息条回调函数委托
/// </summary>
public delegate void DGMsgDiv();
    /// <summary>
    /// 消息条类 带Timer计时
    /// </summary>
public class MsgDiv : System.Windows.Forms.Label
{
    private Timer timerLable = new Timer();
    /// <summary>
    /// 消息回调 委托对象
    /// </summary>
    private DGMsgDiv dgCallBack = null;

    #region 计时器
    /// <summary>
    /// 计时器
    /// </summary>
    public Timer TimerMsg
    {
        get { return timerLable; }
        set { timerLable = value; }
    } 
    #endregion

    #region  MsgDiv构造函数
    /// <summary>
    /// MsgDiv构造函数
    /// </summary>
    public MsgDiv()
    {
        InitallMsgDiv(7, 7);
    }

    /// <summary>
    /// MsgDiv构造函数
    /// </summary>
    /// <param name="x">定位x轴坐标</param>
    /// <param name="y">定位y轴坐标</param>
    public MsgDiv(int x, int y)
    {
        InitallMsgDiv(x, y);
    }
    #endregion

    #region  初始化消息条
    /// <summary>
    /// 初始化消息条
    /// </summary>
    private void InitallMsgDiv(int x, int y)
    {
        this.AutoSize = true;
        this.BackColor = System.Drawing.Color.FromArgb(((int)(((byte)(255)))), ((int)(((byte)(255)))), ((int)(((byte)(192)))));
        this.BorderStyle = System.Windows.Forms.BorderStyle.FixedSingle;
        //this.ContextMenuStrip = this.cmsList;
        this.Font = new System.Drawing.Font("宋体", 11F, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, ((byte)(134)));
        this.ForeColor = System.Drawing.Color.Red;
        this.Location = new System.Drawing.Point(x, y);
        this.MaximumSize = new System.Drawing.Size(980, 525);
        this.Name = "msgDIV";
        this.Padding = new System.Windows.Forms.Padding(7);
        this.Size = new System.Drawing.Size(71, 31);
        this.TabIndex = 1;
        this.Text = "消息条";
        this.Visible = false;
        //给委托添加事件
        this.DoubleClick += new System.EventHandler(this.msgDIV_DoubleClick);
        this.MouseLeave += new System.EventHandler(this.msgDIV_MouseLeave);
        this.MouseHover += new System.EventHandler(this.msgDIV_MouseHover);
        this.timerLable.Interval = 1000;
        this.timerLable.Tick += new System.EventHandler(this.timerLable_Tick);
    }
    #endregion

    #region 将消息条添加到指定容器上
    /// <summary>
    /// 将消息条添加到指定容器上Form
    /// </summary>
    /// <param name="form"></param>
    public void AddToControl(Form form)
    {
        form.Controls.Add(this);
    }
    /// <summary>
    /// 将消息条添加到指定容器上GroupBox
    /// </summary>
    /// <param name="form"></param>
    public void AddToControl(GroupBox groupBox)
    {
        groupBox.Controls.Add(this);
    }
    /// <summary>
    /// 将消息条添加到指定容器上Panel
    /// </summary>
    /// <param name="form"></param>
    public void AddToControl(Panel panel)
    {
        panel.Controls.Add(this);
    }
    #endregion

    //---------------------------------------------------------------------------
    #region 消息显示 的相关参数们 hiddenClick，countNumber，constCountNumber
    /// <summary>
    /// 当前显示了多久的秒钟数
    /// </summary>
    int hiddenClick = 0;
    /// <summary>
    /// 要显示多久的秒钟数 可变参数
    /// </summary>
    int countNumber = 3;
    /// <summary>
    /// 要显示多久的秒钟数 固定参数
    /// </summary>
    int constCountNumber = 3; 
    #endregion

    #region 计时器 显示countNumber秒钟后自动隐藏div -timerLable_Tick(object sender, EventArgs e)
    private void timerLable_Tick(object sender, EventArgs e)
    {
        if (hiddenClick > countNumber - 2)
        {
            MsgDivHidden();
        }
        else
        {
            hiddenClick++;
            //RemainCount();
        }
    } 
    #endregion

    #region 隐藏消息框 并停止计时 +void MsgDivHidden()
    /// <summary>
    /// 隐藏消息框 并停止计时
    /// </summary>
    public void MsgDivHidden()
    {
        this.Text = "";
        this.Visible = false;
        this.hiddenClick = 0;
        //this.tslblRemainSecond.Text = "";
        if (this.timerLable.Enabled == true)
            this.timerLable.Stop();

        //调用 委托 然后清空委托
        if (dgCallBack != null && dgCallBack.GetInvocationList().Length > 0)
        {
            dgCallBack();
            dgCallBack -= dgCallBack;
        }
    } 
    #endregion

    #region 在消息框中显示消息字符串 +void MsgDivShow(string msg)
    /// <summary>
    /// 在消息框中显示消息字符串
    /// </summary>
    /// <param name="msg">要显示的字符串</param>
    public void MsgDivShow(string msg)
    {
        this.Text = msg;
        this.Visible = true;
        this.countNumber = constCountNumber;//默认设置显示秒数为10;
        this.hiddenClick = 0;//重置倒数描述
        this.timerLable.Start();
    } 
    #endregion

    #region 在消息框中显示消息字符串 并在消息消失时 调用回调函数 +void MsgDivShow(string msg, DGMsgDiv callback)
    /// <summary>
    /// 在消息框中显示消息字符串 并在消息消失时 调用回调函数
    /// </summary>
    /// <param name="msg">要显示的字符串</param>
    /// <param name="callback">回调函数</param>
    public void MsgDivShow(string msg, DGMsgDiv callback)
    {
        MsgDivShow(msg);
        dgCallBack = callback;
    }
    #endregion

    #region 在消息框中显示消息字符串 并在指定时间消息消失时 调用回调函数 +void MsgDivShow(string msg, int seconds, DGMsgDiv callback)
    /// <summary>
    /// 在消息框中显示消息字符串 并在消息消失时 调用回调函数
    /// </summary>
    /// <param name="msg">要显示的字符串</param>
    /// <param name="seconds">消息显示时间</param>
    /// <param name="callback">回调函数</param>
    public void MsgDivShow(string msg, int seconds, DGMsgDiv callback)
    {
        MsgDivShow(msg, seconds);
        dgCallBack = callback;
    }  
    #endregion

    #region 在消息框中显示消息字符串，并指定消息框显示秒数 +void MsgDivShow(string msg, int seconds)
    /// <summary>
    /// 在消息框中显示消息字符串，并指定消息框显示秒数
    /// </summary>
    /// <param name="msg">要显示的字符串</param>
    /// <param name="seconds">消息框显示秒数</param>
    public void MsgDivShow(string msg, int seconds)
    {
        this.Text = msg;
        this.Visible = true;
        this.countNumber = seconds;
        this.hiddenClick = 0;//重置倒数描述
        this.timerLable.Start();
    } 
    #endregion

    //---------------------------------------------------------------------------
    #region 事件们～～～！ msgDIV_MouseHover，msgDIV_MouseLeave，msgDIV_DoubleClick
    //当鼠标停留在div上时 停止计时
    private void msgDIV_MouseHover(object sender, EventArgs e)
    {
        if (this.timerLable.Enabled == true)
            this.timerLable.Stop();
    }
    //当鼠标从div上移开时 继续及时
    private void msgDIV_MouseLeave(object sender, EventArgs e)
    {
        //当消息框正在显示、回复框没显示、计时器正停止的时候，重新启动计时器
        if (this.Visible == true && this.timerLable.Enabled == false)
            this.timerLable.Start();
    }
    //双击消息框时关闭消息框
    private void msgDIV_DoubleClick(object sender, EventArgs e)
    {
        MsgDivHidden();
    } 
    #endregion

}

 private void Form1_Load(object sender, EventArgs e)
        {
            msgDiv1.MsgDivShow("嘿嘿", 3, Test);
            //MyTool tool = new MyTool();
            //List<Grade> list = tool.DataTableToList<Grade>(dt);
        }
        public void Test()
        {
            MessageBox.Show("Test");
        }

using System;
using System.Collections.Generic;
using System.Data;
using System.Data.SqlClient;
using System.Linq;
using System.Reflection;
using System.Text;
using System.Threading.Tasks;

namespace MySchool.DAL
{
   public class MyTool
    {
        /// <summary>
        /// DataSetToList
        /// </summary>
        /// <typeparam name="T">转换类型</typeparam>
        /// <param name="dataSet">数据源</param>
        /// <param name="tableIndex">需要转换表的索引</param>
        /// <returns></returns>
        public IList<T> DataTableToList<T>(DataTable dt)
        {
            //确认参数有效
            if (dt == null )
                return null;
            List<T> list = new List<T>();

            for (int i = 0; i < dt.Rows.Count; i++)
            {
                //创建泛型对象
                T _t = Activator.CreateInstance<T>();
                //获取对象所有属性
                PropertyInfo[] propertyInfo = _t.GetType().GetProperties();
                for (int j = 0; j < dt.Columns.Count; j++)
                {
                    foreach (PropertyInfo info in propertyInfo)
                    {
                        //属性名称和列名相同时赋值
                        if (dt.Columns[j].ColumnName.ToUpper().Equals(info.Name.ToUpper()))
                        {
                            if (dt.Rows[i][j] != DBNull.Value)
                            {
                                info.SetValue(_t, dt.Rows[i][j], null);
                            }
                            else
                            {
                                info.SetValue(_t, null, null);
                            }
                            break;
                        }
                    }
                }
                list.Add(_t);
            }
            return list;
        }
    }
}

 public List<Grade> LoadAllGradeToList()
        {
           // List<Grade> list = new List<Grade>();
            string sql = "select * from grade";
            DataTable dt = SQLHelper.ExecuteDataTable(sql);

　　　　　　　　//代替Foreach
            MyTool tool=new MyTool();
           List<Grade> list=tool.DataTableToList<Grade>(dt);
            //将dt转成List<Student>
            //foreach (DataRow row in dt.Rows)
            //{
            //    //每一个row代表表中的一行   所以 一行对应一个年级对象

            //    Grade grade = new Grade();
            //    grade.GradeId = Convert.ToInt32(row["gradeid"]);
            //    grade.GradeName = row["gradename"].ToString();
            //    list.Add(grade);
            //}
            return list;
        }

public class StudentExtends:Student
    {
       //一个是科目名称
       public string SubjectName { get; set; }

       //考试时间
       public DateTime ExamDate { get; set; }


       //成绩
       public int StudentResult { get; set; }
    }

public List<StudentExtends> LoadStudentInfo()
       {
           List<StudentExtends> list=new List<StudentExtends>();
           string sql = @"select studentname,subjectname,studentresult,examdate
                          from student,subject,result
                          where student.studentno=result.studentno
                          and result.subjectid=subject.subjectid";
           DataTable dt=SQLHelper.ExecuteDataTable(sql);
           foreach (DataRow item in dt.Rows)
           {
               //一个item就是表中的一条记录（学生名称，科目名称 ，成绩和时间）
               //一个游离的 学生对象
                StudentExtends stu=new StudentExtends();
                stu.StudentName = item["studentname"].ToString();
                stu.SubjectName = item["subjectname"].ToString();
                stu.StudentResult = Convert.ToInt32(item["studentresult"]);
                stu.ExamDate = Convert.ToDateTime(item["examdate"]);

               list.Add(stu);
           }
           return list;

       }

 public List<StudentExtends> LoadStudentInfo()
      {
         return dal.LoadStudentInfo();
      }

 private void FrmSelectResult_Load(object sender, EventArgs e)
        {
          List<StudentExtends> list=  bll.LoadStudentInfo();
            dgvResult.DataSource = list;
        }