组合查询 分页

分页：

   当前第<asp:Label ID="Label1" runat="server" Text=""></asp:Label>页 
            共<asp:Label ID="Label2" runat="server" Text=""></asp:Label>页 
            <asp:LinkButton ID="LinkButton1" runat="server" >首页</asp:LinkButton>
            <asp:LinkButton ID="LinkButton2" runat="server">上一页</asp:LinkButton>
            <asp:LinkButton ID="LinkButton3" runat="server">下一页</asp:LinkButton>
            <asp:LinkButton ID="LinkButton4" runat="server">末页</asp:LinkButton>
            跳到
            <asp:DropDownList ID="DropDownList1" AutoPostBack="true" runat="server"></asp:DropDownList>
             页

public List<Users> cha(int page,int pagecode)
        {
            List<Users> List = new List<Users>();
            Users u = null;
//注意：sql语句
            com.CommandText = "select top " + pagecode + " *FROM Users where UserName not in (select top " + ((page - 1) * pagecode) + " UserName FROM Users)";
            con.Open();
            SqlDataReader dr = com.ExecuteReader();
            if (dr.HasRows)
            {
                while (dr.Read())
                {
                    u = new Users()
                    {
                        UserName = dr[0].ToString(),
                        PassWord = dr[1].ToString(),
                        NickName = dr[2].ToString(),
                        Sex = Convert.ToBoolean(dr[3]),
                        Birthday = Convert.ToDateTime(dr[4]),
                        Phone = dr[5].ToString(),
                        Email = dr[6].ToString(),
                        Natoin = dr[7].ToString(),
                        Area = dr[8].ToString(),
                    };
                    List.Add(u);
                }
            }
            con.Close();
            return List;
        }

全局变量，每页显示的个数
int pagecode = 5;
 //跳到指定页数
    void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
    {
        int a=Convert.ToInt32(DropDownList1.SelectedValue);//获取页数
       //显示数据
        Repeater1.DataSource = new Usersdata().cha(a, pagecode);
        Repeater1.DataBind();
        Label1.Text = a.ToString();//显示当前页
    }
    //下一页
    void LinkButton3_Click(object sender, EventArgs e)
    {
        Label1.Text = (Convert.ToInt32(Label1.Text) + 1).ToString();//显示下一页
        if (Convert.ToInt32(Label1.Text) <= MAXPAGE(pagecode))//判断是否小于最大页
        {
            Repeater1.DataSource = new Usersdata().cha(Convert.ToInt32(Label1.Text), pagecode);
            Repeater1.DataBind();
        }
        else 
        {          
            Label1.Text = MAXPAGE(pagecode).ToString();
            return;
        }
    }
    //上一页
    void LinkButton2_Click(object sender, EventArgs e)
    {
        Label1.Text =(Convert.ToInt32(Label1.Text) - 1).ToString();//显示上一页
        if (Convert.ToInt32(Label1.Text)<=0)//判断是否大于0页
        {
            Label1.Text = "1";
            return;
        }
        Repeater1.DataSource = new Usersdata().cha(Convert.ToInt32(Label1.Text), pagecode);
        Repeater1.DataBind();
    }
    //末页
    void LinkButton4_Click(object sender, EventArgs e)
    {
        Repeater1.DataSource = new Usersdata().cha(MAXPAGE(pagecode), pagecode);
        Repeater1.DataBind();
        Label1.Text = MAXPAGE(pagecode).ToString();
    }
    //首页
    void LinkButton1_Click(object sender, EventArgs e)
    {
        Repeater1.DataSource = new Usersdata().cha(1, pagecode);
        Repeater1.DataBind();
        Label1.Text = "1";
    }
    
    //最大页数
    private static int MAXPAGE(int pagecode)
    {
        double ye = (new Usersdata().cha().Count) / (pagecode *1.0);
        int maxye = Convert.ToInt32(Math.Ceiling(ye));
        return maxye;
    }


//查找按钮事件

 Hashtable has = new Hashtable();//实例化哈希表，作用防攻击

       //拼sql语句
        string sqls = "select *from Users ";
        if(TextBox1.Text!="")
        {
            sqls += " where UserName like @a";
            has.Add("@a", "%" + TextBox1.Text.Trim() + "%");//将用户输入的内容放进哈希表，防攻击
            count++;
        }
        if(Drop_nation.SelectedValue !="0")
        {
            if(count !=0)//如果上面有查询条件接and
            {
                sqls += " and Nation=@b";
                
            }
            else//如果上面没有查询条件接where
            {
                sqls += " WHERE Nation=@b";
                
                count++;
            }
            string sss=Drop_nation.SelectedValue.ToString();
            has.Add("@b",sss );
            count++;
        }

      //Repeater数据绑定
      Repeater1.DataSource = new Usersdata().chas(sqls,has);
      Repeater1.DataBind();
      count = 0;

public List<Users> chas(string s,Hashtable has)  //语句 哈希表
        {
            List<Users> List = new List<Users>();
            Users u = null;
            com.CommandText = s;
            com.Parameters.Clear();
            foreach(string aa in has.Keys)
            {
                com.Parameters.Add(aa,has[aa]);            
            }
            con.Open();
            SqlDataReader dr = com.ExecuteReader();
            if (dr.HasRows)
            {
                while (dr.Read())
                {
                    u = new Users()
                    {
                        UserName = dr[0].ToString(),
                        PassWord = dr[1].ToString(),
                        NickName = dr[2].ToString(),
                        Sex = Convert.ToBoolean(dr[3]),
                        Birthday = Convert.ToDateTime(dr[4]),
                        Phone = dr[5].ToString(),
                        Email = dr[6].ToString(),
                        Natoin = dr[7].ToString(),
                        Area = dr[8].ToString(),
                    };
                    List.Add(u);
                }
            }
            con.Close();
            return List;
        }