Webform（分页、组合查询）

一、分页

1.写查询方法：

 public List<Student> Select(int PageCount, int PageNumber)
    {//PageCount为每页显示条数，PageNumber为当前第几页
        List<Student> list = new List<Student>();
        cmd.CommandText = "select top " + PageCount + "  *from Student where Code not in (select top "+(PageCount * (PageNumber - 1))+" Code from Student)";
        conn.Open();
        SqlDataReader dr = cmd.ExecuteReader();
        if (dr.HasRows)
        {
            while (dr.Read())
            {
                Student s = new Student();
                s.Code = dr[0].ToString();
                s.Name = dr[1].ToString();
                s.Sex = Convert.ToBoolean(dr[2]);
                s.Birthday = Convert.ToDateTime(dr[3]);
                s.SubjectCode = dr[4].ToString();
                s.Nation = dr[5].ToString();
                list.Add(s);
            }
        }
        conn.Close();
        return list;
    }

2.C#代码

  int PageCount = 5; //每页显示条数
    protected void Page_Load(object sender, EventArgs e)
    {
        if(!IsPostBack)
        {
        List<Student> list = new StudentData().Select(PageCount,1);
        Repeater1.DataSource = list;
        Repeater1.DataBind();
        Label2.Text = "1";//第一页
        Label3.Text = MaxPageNumber().ToString();//总页数
}
  for (int i = 1; i <= MaxPageNumber(); i++)
    {
        DropDownList2.Items.Add(new ListItem(i.ToString(), i.ToString()));
    }
}

  public int MaxPageNumber()
    {
        List<Student> list = new StudentData().select();

        double de = list.Count / (PageCount * 1.0);

        int aa = Convert.ToInt32(Math.Ceiling(de));//取上限
        return aa;
    }

  void DropDownList2_SelectedIndexChanged(object sender, EventArgs e)
    {
        Repeater1.DataSource = new StudentData().Select(PageCount, Convert.ToInt32(DropDownList2.SelectedValue));
        Repeater1.DataBind();
        Label2.Text = DropDownList2.SelectedValue;
    }

 void btn_end_Click(object sender, EventArgs e)
    {
        List<Student> list = new StudentData().Select(PageCount, MaxPageNumber());
        Repeater1.DataSource = list;
        Repeater1.DataBind();
        Label2.Text = MaxPageNumber().ToString();
    }

  void btn_first_Click(object sender, EventArgs e)
    {
        List<Student> list = new StudentData().Select(PageCount, 1);
        Repeater1.DataSource = list;
        Repeater1.DataBind();
        Label2.Text ="1";
    }

 void btn_prev_Click(object sender, EventArgs e)
    {
        int pagec = Convert.ToInt32(Label2.Text) - 1;
        if (pagec <=0)//判断是不是第一页，是的话什么也不干
        {
            return;
        }
        List<Student> list = new StudentData().Select(PageCount, pagec);
        Repeater1.DataSource = list;
        Repeater1.DataBind();
        Label2.Text = pagec.ToString();
    }

 void btn_next_Click(object sender, EventArgs e)
    {
         int pagec = Convert.ToInt32(Label2.Text) + 1;
         if (pagec > MaxPageNumber())// 判断是不是最后一页，是的话什么也不干
         {
             return;
         }
        Repeater1.DataSource = new StudentData().Select(PageCount,pagec);
        Repeater1.DataBind();
        Label2.Text = pagec.ToString();

    }

二、组合查询

1.查询方法

  public List<Student> Select(string tsql,Hashtable hh)
    {
        List<Student> list = new List<Student>();
        cmd.CommandText = tsql;
        cmd.Parameters.Clear();
        foreach( string s in hh.Keys)
        {
        cmd.Parameters.Add(s,hh[s]);
        }
        conn.Open();
        SqlDataReader dr = cmd.ExecuteReader();
        if (dr.HasRows)
        {
            while (dr.Read())
            {
                Student s = new Student();
                s.Code = dr[0].ToString();
                s.Name = dr[1].ToString();
                s.Sex = Convert.ToBoolean(dr[2]);
                s.Birthday = Convert.ToDateTime(dr[3]);
                s.SubjectCode = dr[4].ToString();
                s.Nation = dr[5].ToString();
                list.Add(s);
            }
        }
        conn.Close();
        return list;
    }

public List<Subject> Select(string name)
    {
        List<Subject> list = new List<Subject>();
        cmd.CommandText = "select *from Subject where SubjectName like @a ";
        cmd.Parameters.Clear();
        cmd.Parameters.Add("@a","%"+name+"%");
        conn.Open();
        SqlDataReader dr = cmd.ExecuteReader();
        if (dr.HasRows)
        {
            while (dr.Read())
            {
                Subject s = new Subject();
                s.SubjectCode = dr[0].ToString();
                s.SubjectName = dr[1].ToString();
                list.Add(s);
            }
        }
        conn.Close();

        return list;
    }

2.c#代码

  void Button2_Click(object sender, EventArgs e)
    {
        int count = 0;//判断tsql是否含有where
        Hashtable hs = new Hashtable();//哈希表
        string tsql = "select * from Student";
        //性别
        if(!string.IsNullOrEmpty(tb_sex.Text.Trim()))//输入的性别非空
        {
            if (tb_sex.Text.Trim() == "男")
            {
                tsql += " where Sex = @a";
                hs.Add("@a", "true");
                count++;
            }
            else if (tb_sex.Text.Trim() == "女")
            {
                tsql += " where Sex = @a";
                hs.Add("@a", "false");
                count++;
            }          
        }
        //年龄
        if (!string.IsNullOrEmpty(tb_age.Text.Trim()))//判断年龄输入框是否为空
        { 
            int a = DateTime.Now.Year;
            try {//异常保护，输入框只能是数字
             int ag=  Convert.ToInt32(tb_age.Text.Trim());
             int g = a - ag;
             DateTime d = Convert.ToDateTime(g.ToString()+"-1-1");
             if (DropDownList3.SelectedValue == ">=")//列表框显示值为<=,小于某个年龄
             {
                 if (count == 0)
                 {
                     tsql += " where Birthday " + DropDownList3.SelectedValue + "@b";
                 }
                 else
                 {
                     tsql += " and Birthday " + DropDownList3.SelectedValue + "@b";
                 }
                 hs.Add("@b", d);
             }
             else//大于某个年龄
             {
                 DateTime dd = Convert.ToDateTime(g.ToString() + "-12-31");
                 if (count == 0)
                 {
                     tsql += " where Birthday " + DropDownList3.SelectedValue + "@b";
                 }
                 else
                 {
                     tsql += " and Birthday " + DropDownList3.SelectedValue + "@b";
                 }
                 hs.Add("@b", dd);
             }
             count++;
            }
            catch { 
            }          
        }
        if (!string.IsNullOrEmpty(tb_s.Text.Trim()))//专业非空
        {
            List<Subject> li = new SubjectData().Select(tb_s.Text.Trim());
            if (li.Count <= 0)
            {
            }
            else
            { string u ="";
            int cou = 0;
                foreach(Subject ub in li)
                {
                    u = ub.SubjectCode;
                    if (cou == 0)//第一条数据
                    {
                        if (count == 0)
                        {
                            tsql += " where SubjectCode =@c";
                        }
                        else
                        {
                            tsql += " and SubjectCode =@c";
                        }
                        hs.Add("@c", u);
                        cou++;
                    }
                    else
                    {
                        tsql += " or SubjectCode =@d";
                        hs.Add("@d", u);
                    }
                }
            }
        }
        Repeater1.DataSource = new StudentData().Select(tsql, hs);
        Repeater1.DataBind();
    }