学生管理系统（三层架构）

首先我们先创建UI层

Student.UI

我们看一下窗体框架（参照上图顺序）

接下来我们看一下Model层

我们就以Model里面Studeng.cs类里面谁写的代码为例(数据根据库表里面的数据来写)。

public class Student
    {
        //编号
        private int studentNo;
        public int StudentNo
        {
            get { return studentNo; }
            set { studentNo = value; }
        }
        //密码
        private string loginPwd;
        public string LoginPwd
        {
            get { return loginPwd; }
            set { loginPwd = value; }
        }
       ...
}

紧接着我们来看一下DAL层(StudentDAL)

GradeDAL.cs

 public class GradeDAL
    {
       //01.检索所有的年级名称集合，返回的是泛型集合List<Grade>
        public List<Grade> getAllGradeList()
        {
            string sql = "select * from grade";
            //1.1 强SQL 转成内存中的一个张表
            DataTable dt=SQLHelper.ExecuteDataTable(sql);
            MyTool tool=new MyTool();
            //dt转List
            List<Grade> list = tool.DataTableToList<Grade>(dt);
            return list;
        }
    }

MyTool.cs(自定义工具类)

 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 List<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;
        }
    }

ResultDAL

public class ResultDAL
    {
        public List<ResultExt> getAllResult()
        {
            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);
            MyTool tool=new MyTool();
            List<ResultExt> list = tool.DataTableToList<ResultExt>(dt);
            return list;
        }

        public List<ResultExt> getResultByParameter(int subjectid,string stuname)
        {
            string sql = "select studentname,subjectname,studentresult,examdate from student,subject,result where student.studentno=result.studentno and result.subjectid=subject.subjectid ";

            if (subjectid!=-1)
            {
                sql += " and result.subjectid=@subid";
            }
            if (!string.IsNullOrEmpty(stuname))//null ""
            {
                sql += " and studentname like @name";
            }
            SqlParameter[] para =
            {
                new SqlParameter("@subid",subjectid), 
                new SqlParameter("@name",'%'+stuname+'%')
            };


            DataTable dt = SQLHelper.ExecuteDataTable(sql,para);
            MyTool tool = new MyTool();
            List<ResultExt> list = tool.DataTableToList<ResultExt>(dt);
            return list;
        }

    }

SQLHelper

public static  class SQLHelper
    {
      public static string Constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
      public static int id;
      /// <summary>
      /// 执行NonQuery命令
      /// </summary>
      /// <param name="cmdTxt"></param>
      /// <param name="parames"></param>
      /// <returns></returns>
      public static int ExecuteNonQuery(string cmdTxt, params SqlParameter[] parames)
      {
          return ExecuteNonQuery(cmdTxt, CommandType.Text, parames);
      }
      //可以使用存储过程的ExecuteNonquery
      public static int ExecuteNonQuery(string cmdTxt, CommandType cmdtype, params SqlParameter[] parames)
      {
          //判断脚本是否为空 ，直接返回0
          if (string.IsNullOrEmpty(cmdTxt))
          {
              return 0;
          }
          using (SqlConnection con = new SqlConnection(Constr))
          {
              using (SqlCommand cmd = new SqlCommand(cmdTxt, con))
              {
                  if (parames != null)
                  {
                      cmd.CommandType = cmdtype;
                      cmd.Parameters.AddRange(parames);
                  }
                  con.Open();
                  return cmd.ExecuteNonQuery();
              }
          }
      }
      public static SqlDataReader ExecuteDataReader(string cmdTxt, params SqlParameter[] parames)
      {
          return ExecuteDataReader(cmdTxt, CommandType.Text, parames);
      }
      //SQLDataReader存储过程方法
      public static SqlDataReader ExecuteDataReader(string cmdTxt, CommandType cmdtype, params SqlParameter[] parames)
      {
          if (string.IsNullOrEmpty(cmdTxt))
          {
              return null;
          }
          SqlConnection con = new SqlConnection(Constr);

          using (SqlCommand cmd = new SqlCommand(cmdTxt, con))
          {
              cmd.CommandType = cmdtype;
              if (parames != null)
              {
                  
                  cmd.Parameters.AddRange(parames);
              }
              con.Open();
              //把reader的行为加进来。当reader释放资源的时候，con也被一块关闭
              return cmd.ExecuteReader(System.Data.CommandBehavior.CloseConnection);
          }

      }
      //params 可变参数
      public static DataTable ExecuteDataTable(string sql, params SqlParameter[] parames)
      {
          return ExecuteDataTable(sql, CommandType.Text, parames);
      }
      //调用存储过程的类，关于(ExecuteDataTable)
      public static DataTable ExecuteDataTable(string sql, CommandType cmdType, params SqlParameter[] parames)
      {
          if (string.IsNullOrEmpty(sql))
          {
              return null;
          }
          DataTable dt = new DataTable();
          using (SqlDataAdapter da = new SqlDataAdapter(sql, Constr))
          {
              da.SelectCommand.CommandType = cmdType;
              if (parames != null)
              {
                  da.SelectCommand.Parameters.AddRange(parames);
              }
              da.Fill(dt);
              return dt;
          }
      }
    
      /// <summary>
      /// ExecuteScalar
      /// </summary>
      /// <param name="cmdTxt">第一个参数，SQLServer语句</param>
      /// <param name="parames">第二个参数，传递0个或者多个参数</param>
      /// <returns></returns>
      public static object ExecuteScalar(string cmdTxt, params SqlParameter[] parames)
      {
          return ExecuteScalar(cmdTxt, CommandType.Text, parames);
      }
      //可使用存储过程的ExecuteScalar
      public static object ExecuteScalar(string cmdTxt, CommandType cmdtype, params SqlParameter[] parames)
      {
          if (string.IsNullOrEmpty(cmdTxt))
          {
              return null;
          }
          using (SqlConnection con = new SqlConnection(Constr))
          {
              using (SqlCommand cmd = new SqlCommand(cmdTxt, con))
              {
                  cmd.CommandType = cmdtype;
                  if (parames != null)
                  {
                      cmd.Parameters.AddRange(parames);
                  }
                  con.Open();
                return   cmd.ExecuteScalar();
              }
          }  
      }
      //调用存储过程的DBHelper类（关于ExeceutScalar,包含事务,只能处理Int类型，返回错误号）
      public static object ExecuteScalar(string cmdTxt, CommandType cmdtype,SqlTransaction sqltran, params SqlParameter[] parames)
      {
           if (string.IsNullOrEmpty(cmdTxt))
          {
              return 0;
          }
          using (SqlConnection con = new SqlConnection(Constr))
          {
              int sum = 0;
              using (SqlCommand cmd = new SqlCommand(cmdTxt, con))
              {
                  cmd.CommandType=cmdtype;
                  if (parames != null)
                  {
                      cmd.Parameters.AddRange(parames);
                  }
                  con.Open();
                  sqltran = con.BeginTransaction();
                  try
                  {
                      cmd.Transaction = sqltran;
                      sum=Convert.ToInt32( cmd.ExecuteScalar());
                      sqltran.Commit();
                  }
                  catch (SqlException ex)
                  {
                      sqltran.Rollback();
                  }
                  return sum;
              }
          }
      }
    }

StudentDAL

 public class StudentDAL
    {
        public List<Student> GetAllStudentList()
        {
            string sql = "select * from student";
            DataTable dt = SQLHelper.ExecuteDataTable(sql); 
            MyTool tool=new MyTool();
            List<Student> list = tool.DataTableToList<Student>(dt);
            
            return list;
           
        }

        public DataTable GetAllStudent()
        {
            string sql = "select * from student";
            DataTable dt = SQLHelper.ExecuteDataTable(sql);
            return dt;
        }


        public bool IsLogin(Student stu)
        {
            bool flag = false;
            string sql = "select count(1) from student where studentno='"+stu.SName+"' and loginpwd='"+stu.LoginPwd+"'";
            int count=Convert.ToInt32(SQLHelper.ExecuteScalar(sql));
            if (count>0)
            {
                flag = true;
            }
            return flag;
        }
    }

SubjectDAL

 public class SubjectDAL
    {
       //01.写一个根据年级编号检索该年级下所有科目集合的方法
       public List<Subject> getAllSubjectByGradeId(int id)
       {
           string sql = "select * from subject where gradeid=@id";
           SqlParameter para = new SqlParameter("@id",id);
           DataTable dt=SQLHelper.ExecuteDataTable(sql, para);
           MyTool tool=new MyTool();
           List<Subject> list = tool.DataTableToList<Subject>(dt);
           return list;
       }
    }

我们在来看一下BLL层(StudentBLL)BLL层用于连接UI层和DAL层

在这里我们就简单的看一下StudentBLL.cs类里面的代码

public class StudentBLL
    {
       public List<Student> GetAllStudent()
       {
           List<Student> list=dal.GetAllStudentList();
           //DataTable dt= dal.GetAllStudent();
           return list;
       }

       StudentDAL dal=new StudentDAL();
      

       public bool IsLogin(Student stu)
       {
          bool result= dal.IsLogin(stu);
           return result;
       }
       
    }

最后就是向UI层填写完整代码了

登录窗体

登录

       StudentBLL bll = new StudentBLL();
       //确定按钮
        private void btnLogin_Click(object sender, EventArgs e)
        {
            //1.1 拼接处一个Student对象，并且赋值
            Student stu=new Student();
            stu.SName = txtName.Text;
            stu.LoginPwd = txtPwd.Text;

            //1.2 调用 bll层的对应的登录方法，传入student对象
            bool flag = bll.IsLogin(stu);
            if (flag)
            {
                MessageBox.Show("success");
            }
        }

登录类型

查询窗体

        
        GradeBLL gradebll=new GradeBLL();
        SubjectBLL subBll=new SubjectBLL();
        ResultBLL resultBll=new ResultBLL();
        private bool flag;
        //Load事件
        private void FrmSelectResultM1_Load(object sender, EventArgs e)
        {
            dgvResult.AutoGenerateColumns = false;
            LoadGrade();
            List<ResultExt> list = resultBll.getAllResult();
            dgvResult.DataSource = list;
        }

        public void LoadGrade()
        {
            cboSubject.DropDownHeight = 106;
            //01.对年级下拉框绑定数据
            List<Grade> list = gradebll.getAllGradeList();

            //两行代码()
            cboGrade.ValueMember = "gradeId";
            cboGrade.DisplayMember = "gradeName";
            cboGrade.DataSource = list;
            flag = true;
        }

        //年级下拉框选中项改变的事件
        private void cboGrade_SelectedIndexChanged(object sender, EventArgs e)
        {
            
                //1.1  先获取到选中的年级名称对应的年级编号
                //如何获取下拉框的隐藏值  （）
                int selectid = Convert.ToInt32(cboGrade.SelectedValue);
                //code a little ,debug a little
                //1.2  介入BLL ，调用方法，传入ID，获取List<Subject>
                List<Subject> list = subBll.getAllSubjectByGradeId(selectid);

                Subject sub=new Subject();
                sub.SubjectId = -1;
                sub.SubjectName = "请选择";

                list.Insert(0,sub);
                cboSubject.DataSource = list;
                //两行代码()
                cboSubject.ValueMember = "subjectId";
                cboSubject.DisplayMember = "subjectName";
        }

       //查询
        private void btnSearch_Click(object sender, EventArgs e)
        {
            //下拉框隐藏值
            int subid = Convert.ToInt32(cboSubject.SelectedValue);
            //文本框的值
            string name = txtName.Text;
            List<ResultExt> list = resultBll.getResultByParameter(subid, name);
            dgvResult.DataSource = list;
        }

显示全部信息窗体

StudentBLL bll=new StudentBLL();
        private void FrmStuList_Load(object sender, EventArgs e)
        {
         List<Student> list=   bll.GetAllStudent();
            dgvList.DataSource = list;
        }