高级查询--asp.net(C#)

为了更好的去重用高级查询控件，将此控件做成用户控件。利用VS2005新建一个用控件扩展名为.ascx的文件，参考下图： 

       本高级查询的原理是：当用户选择选择内容时，相应的筛选条件，筛选范围进行动态的变化。将筛选条件保存在lblFilter标签中。利用DataView的RowFilter，对数据进行筛选，但为了更好的管理，将这些配置信息保存在表中。注：以下是对应的html源代码：

<%...@ Control Language="C#" AutoEventWireup="true" CodeFile="Advance_Query.ascx.cs"
    Inherits="Public_AdvanceQuery" %>
    <br />
    <table border="1" bordercolor="#ffffff" cellpadding="0" cellspacing="1" width="100%">
        <tr>
        
            <td style="height: 15px">
                筛选内容：</td>
            <td style="height: 15px">
                <asp:DropDownList ID="ddlContent" runat="server" AutoPostBack="True" OnSelectedIndexChanged="ddlContent_SelectedIndexChanged">
                </asp:DropDownList></td>
            <td style="height: 15px">
                筛选条件：</td>
            <td style="height: 15px">
                <asp:DropDownList ID="ddlCondition" runat="server">
                </asp:DropDownList></td>
            <td  style="height: 15px">
                筛选范围：</td>
            <td style="height: 15px">
                &nbsp;<asp:DropDownList ID="ddlArea" runat="server">
                </asp:DropDownList>
                <asp:TextBox ID="txtArea" runat="server"></asp:TextBox>
                <asp:Label ID="lblFilter" runat="server" Visible="False"></asp:Label>
            </td>
            <td style="height: 15px">
                <asp:Button ID="btnSel" runat="server" OnClick="btnSel_Click" Text="筛选" />
                <asp:Button ID="btnCancel" runat="server" OnClick="btnCancel_Click"
                    Text="取消" /></td>                   
        </tr>
    </table>
    <br />

        以下是本页面对应的后台代码，主要是事件，属性，方法

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
/**//// <summary>
/// 高级查询用户控件
/// 创建人：AAA
/// 创建日期：2006-08-29
/// </summary>
public partial class Public_AdvanceQuery : System.Web.UI.UserControl
...{
    //定义类
    WebClass.Query query;
    protected void Page_Load(object sender, EventArgs e)
    ...{
        if (!Page.IsPostBack)
        ...{
            this._gv.DataSource = this._dv;
            this._gv.DataBind();
            //设置筛选内容
            this.Load_ddlContent();
        }
    }
    protected void ddlContent_SelectedIndexChanged(object sender, EventArgs e)
    ...{
        query = new WebClass.Query(this._form);
        if (query.Get_Content_Flag(this.ddlContent.SelectedValue) == "0")
        ...{
            this.ddlArea.Items.Clear();
            this.ddlArea.DataSource = query.DataSet_Area(ddlContent.SelectedValue);
            this.ddlArea.DataTextField = "Name";
            this.ddlArea.DataValueField = "Code";
            this.ddlArea.DataBind();
            //文本框不可见
            this.txtArea.Visible = false;
            this.ddlArea.Visible = true;
        }
        else
        ...{
            this.txtArea.Text = "";
            this.txtArea.Visible = true;
            this.ddlArea.Visible = false;
        }
        query.Set_Condition(this.ddlContent.SelectedValue, this.ddlCondition);
    }
    protected void btnSel_Click(object sender, EventArgs e)
    ...{
        query = new WebClass.Query(this._form);
        //将筛选范围的值存储在文本框里
        if (this.txtArea.Text == "")
            this.txtArea.Text = this.ddlArea.SelectedValue;
        if (btnSel.Text == "筛选")
        ...{
            this.btnSel.Text = "继续进行筛选";
            this.btnCancel.Text = "取消筛选";
        }
        if (this.lblFilter.Text == "")
            this.lblFilter.Text = query.Filter(this.ddlContent.SelectedValue, this.ddlCondition.SelectedValue, this.txtArea.Text);
        else
            this.lblFilter.Text += " AND " + query.Filter(this.ddlContent.SelectedValue, this.ddlCondition.SelectedValue, this.txtArea.Text);
        //定义DataView
        DataView dv = new DataView();
        dv = this._dv;
        dv.RowFilter = this.lblFilter.Text;
        this._gv.DataSource = dv;
        this._gv.DataBind();
        //清空文本框里的内容
        this.txtArea.Text = "";
    }
    protected void btnCancel_Click(object sender, EventArgs e)
    ...{
        DataView dv = new DataView();
        this.btnSel.Text = "筛选";
        this.btnCancel.Text = "取消";
        this.lblFilter.Text = "";
        dv = this._dv;
        this._gv.DataSource = dv;
        this._gv.DataBind();
    } 
    public void Load_ddlContent()
    ...{

        query = new WebClass.Query(this._form);   
        //设置筛选内容
        this.ddlContent.Items.Clear();
        this.ddlContent.DataSource = query.DataSet_Content();
        this.ddlContent.DataTextField = "By_Name";
        this.ddlContent.DataValueField = "Field";
        this.ddlContent.DataBind();
        //设置筛选条件
        query.Set_Condition(ddlContent.SelectedValue, this.ddlCondition);
        //设置筛选范围
        if (query.Get_Content_Flag(ddlContent.SelectedValue) == "0")
        ...{
            this.ddlArea.Items.Clear();
            this.ddlArea.DataSource = query.DataSet_Area(ddlContent.SelectedValue);
            this.ddlArea.DataTextField = "Name";
            this.ddlArea.DataValueField = "Code";
            this.ddlArea.DataBind();
            //文本框不可见
            this.txtArea.Visible = false;
            this.ddlArea.Visible = true;
        }
        else
        ...{
            this.txtArea.Text = "";
            this.txtArea.Visible = true;
            this.ddlArea.Visible = false;
        }
        query.Set_Condition(this.ddlContent.SelectedValue, this.ddlCondition);
    }
    /**//// <summary>
    /// 当前的窗体
    /// </summary>
    private string _form;
    /**//// <summary>
    /// 数据源
    /// 注：数据类型 DataView
    /// </summary>
    private DataView _dv;
    /**//// <summary>
    /// GridView控件
    /// </summary>
    private GridView _gv;
    /**//// <summary>
    /// 设置窗体名称
    /// 注：只写属性
    /// </summary>
    public string strForm
    ...{
        set
        ...{
            this._form = value;
        }
    }
    /**//// <summary>
    /// 设置查询的数据源
    /// 注：只写属性 类型：DataView
    /// </summary>
    public DataView DataSource
    ...{
        set
        ...{
            this._dv = value;
        }
    }
    /**//// <summary>
    /// 设置GridView控件
    /// </summary>
    public GridView GridViewID
    ...{
        set
        ...{
            this._gv = value;
        }
    }
    /**//// <summary>
    /// 获取筛选字符串/设置筛选条件
    /// </summary>
    public string Filter
    ...{
        get
        ...{
            if (this.lblFilter.Text == "")
                return "";
            else
                return this.lblFilter.Text;
        }
        set
        ...{
            this.lblFilter.Text = value;
        }
    }
    public delegate void ButtonClickEventHandler(object sender, System.EventArgs e);
    //public event ButtonClickEventHandler SelClick;
    public delegate void eventhandler(object sender, EventArgs e);
    //public event eventhandler CalClick;
}

using System;
using System.Collections.Generic;
using System.Text;
using System.Web.UI.WebControls;
using System.Data;
using System.Data.SqlClient;

namespace WebClass
...{
    /**//// <summary>
    /// 高级查询
    /// 书写人：AAA
    /// 创建日期：2006-08-28
    /// </summary>
    public class Query:DBClass.DBClass
    ...{
        /**//// <summary>
        /// 当前的窗体名称
        /// </summary>
        private string _strQueryForm;
        /**//// <summary>
        /// 构造函数
        /// </summary>
        /// <param name="QueryForm">高级查询对应的窗体</param>
        /// <param name="ECode">当前的企业编号</param>
        public Query (string QueryForm)
        ...{
            _strQueryForm = QueryForm;
        }
        /**//// <summary>
        /// 获取当前窗体对应的筛选内容的数据集
        /// </summary>
        /// <returns>数据集</returns>
        public DataSet DataSet_Content()
        ...{
            string mysql = string.Format("SELECT By_Name,Field FROM Advance_Query WHERE form='{0}'", this._strQueryForm);

            return base.ExecuteSqlDs(mysql, "Content");
        }
        /**//// <summary>
        /// 设置筛选条件
        /// </summary>
        ///&nb