webform组合查询和分页

1、组合查询
(1)数据访问类

//参数1：SQL语句 参数2：哈希表
public List<Users> chas(string s,Hashtable has)
        {
            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[].ToString(),
                        PassWord = dr[].ToString(),
                        NickName = dr[].ToString(),
                        Sex = Convert.ToBoolean(dr[]),
                        Birthday = Convert.ToDateTime(dr[]),
                        Phone = dr[].ToString(),
                        Email = dr[].ToString(),
                        Natoin = dr[].ToString(),
                        Area = dr[].ToString(),
                    };
                    List.Add(u);
                }
            }
            con.Close();
            return List;
        }

（2）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 !="")
        {
            if(count !=)//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;

2、分页
前台

           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

后台

（1）数据访问类

//参数1：第几页 参数2：每页显示的个数
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 - ) * pagecode) + " UserName FROM Users)";
            con.Open();
            SqlDataReader dr = com.ExecuteReader();
            if (dr.HasRows)
            {
                while (dr.Read())
                {
                    u = new Users()
                    {
                        UserName = dr[].ToString(),
                        PassWord = dr[].ToString(),
                        NickName = dr[].ToString(),
                        Sex = Convert.ToBoolean(dr[]),
                        Birthday = Convert.ToDateTime(dr[]),
                        Phone = dr[].ToString(),
                        Email = dr[].ToString(),
                        Natoin = dr[].ToString(),
                        Area = dr[].ToString(),
                    };
                    List.Add(u);
                }
            }
            con.Close();
            return List;
        }

（2）

//全局变量，每页显示的个数
int pagecode = ;
 //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) + ).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) - ).ToString();//显示上一页
        if (Convert.ToInt32(Label1.Text)<=)//判断是否大于0页
        {
            Label1.Text = "";
            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(, pagecode);
        Repeater1.DataBind();
        Label1.Text = "";
    }

    //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;
    }

3 组合查询和分页结合使用
先查询后分页（拼SQL语句）

数据访问类:同上面的组合查询

        string sqls = "select top " + pagecode + " *from Users ";//带分页和查询条件的SQL语句
        string sql2 = "select *from Users";//带查询条件的SQL的语句
        string sqls1 = "";//查询条件sql语句
        if (TextBox1.Text != "")
        {
            sqls += " where UserName like @a";
            sqls1 += " where UserName like @a";
            has.Add("@a", "%" + TextBox1.Text.Trim() + "%");
            count++;
        }
        if (Drop_nation.SelectedValue != "")
        {
            if (count != )
            {
                sqls += " and Nation=@b";
                sqls1 += " and Nation=@b";
            }
            else
            {
                sqls += " WHERE Nation=@b";
                sqls1 += " WHERE Nation=@b";
                count++;
            }
            string sss = Drop_nation.SelectedValue.ToString();
            has.Add("@b", sss);
            count++;
        }

 if (count > )
        {
            sqls += " and UserName not in (select top " + ((Convert.ToInt32(Label1.Text) - ) * pagecode) + " UserName from Users" + sqls1 + ")";
        }
        else
        {
            sqls += " where UserName not in (select top " + ((Convert.ToInt32(Label1.Text) - ) * pagecode) + " UserName from Users)";
        }
//用label记录sql语句并隐藏，当上一页、下一页等可以从label中取出用

Label3.Text = sqls;
Label4.Text = sqls1;
Label5.Text = sql2 + sqls1;

//Repeater数据绑定
       Repeater1.DataSource = new Usersdata().chas(Label3.Text, has);
        Repeater1.DataBind();