HOW TO:利用Excel的QueryTable下载网上数据-.NET教程,.NET Framework

author:水如烟

总目录：行政区划数据方案设计

这里所说的网上数据,是基于:
一、有固定网址发布最新数据的链接；
二、数据格式固定。

在去年的10月，曾写了个《全国县及县以上行政区划代码信息类》
见：http://www.cnblogs.com/lzmtw/archive/2005/10/22/260066.html

现在仍以行政区划代码数据为例。

行政区划代码数据由国家统计局发布，网址为
http://www.stats.gov.cn/tjbz/xzqhdm/index.htm
数据格式是固定的：
如最新的为2005年12月31日
http://www.stats.gov.cn/tjbz/xzqhdm/t20041022_402301029.htm
最旧的为2001年10月的，
http://www.stats.gov.cn/tjbz/xzqhdm/t20021125_46781.htm

但是有例外，这在代码中说。

方案组织：

效果：

以下为代码：
netconst.vb

namespace net
    public class netconst
        private sub new()
        end sub

        public const gov_default as string = "www.stats.gov.cn"
        public const gov_address as string = "http://www.stats.gov.cn/tjbz/xzqhdm/"
        public const webtable_index as string = "9"
    end class
end namespace

netinformation.vb

imports system.net
imports system.io
imports system.text.regularexpressions

namespace net
    public class netinformation
        private gnetupdateinformations(-1) as netupdateinformationitem

        public readonly property updateinformationstable() as datatable
            get
                return getupdateinformationstable()
            end get
        end property

        private function getupdateinformationstable() as datatable
            dim mdatatable as new datatable("updateinformations")
            with mdatatable
                .columns.add("address")
                .columns.add("lastdate")
                for each item as netupdateinformationitem in gnetupdateinformations
                    .rows.add(new string() {item.address, item.lastdate})
                next
                .acceptchanges()
            end with
            return mdatatable
        end function

        public sub downloadinformationsfromnet()

            dim mregex as new regex("(?<date>2.*日)")

            dim mnetupdateitems as netupdateitem() = getnetupdateitems()
            dim mnetupdateinformationitem as netupdateinformationitem

            dim tmp as netupdateitem
            由于后两个不合规则，舍去不用。最后一个没有日期，倒数第二个提供的是附件数据。
            for i as integer = 0 to mnetupdateitems.length - 1 - 2
                tmp = mnetupdateitems(i)

                mnetupdateinformationitem = new netupdateinformationitem
                with mnetupdateinformationitem
                    .address = tmp.address
                    .lastdate = ctype(mregex.match(tmp.content).value, date).tostring("yyyymmdd")
                end with

                appenditem(of netupdateinformationitem)(mnetupdateinformationitem, gnetupdateinformations)
            next
        end sub

        private function getnetupdateitems() as netupdateitem()

            dim mresult(-1) as netupdateitem

            dim mregex as new regex("<a href=(?<href>.*) target=_blank >(?<content>.*行政区划代码.*)</a>")
            dim mcollection as matchcollection

            dim mclient as new webclient()

            dim mstream as stream = mclient.openread(netconst.gov_address)
            dim mreader as new streamreader(mstream, system.text.encoding.default)
            dim mtext as string = mreader.readtoend

            mreader.close()
            mstream.close()
            mclient.dispose()

            mcollection = mregex.matches(mtext)

            dim tmpitem as netupdateitem
            for each m as match in mcollection
                tmpitem = new netupdateitem
                with tmpitem
                    .address = netconst.gov_address & m.groups(1).value
                    .content = m.groups(2).value
                end with

                appenditem(of netupdateitem)(tmpitem, mresult)
            next

            return mresult
        end function

        private structure netupdateitem
            public address as string
            public content as string
        end structure

        private structure netupdateinformationitem
            public address as string
            public lastdate as string
        end structure

        private sub appenditem(of t)(byval value as t, byref array as t())
            redim preserve array(array.length)
            array(array.length - 1) = value
        end sub

    end class

end namespace

excelquerytable.vb

option strict off

namespace net
    public class excelquerytable
        private gexcelapplication as object
        private gworkbook as object
        private gworksheet as object
        private gquerytable as object

        sub new()
            initialize()
        end sub

        private sub initialize()
            gexcelapplication = createobject("excel.application")
            gexcelapplication.displayalerts = false 使退出时不询问是否存盘
            gworkbook = gexcelapplication.workbooks.add
            gworksheet = gworkbook.worksheets.add
        end sub

        这里只作简单处理,详细处理在我的blog上有相关“文章”作过介绍
        public sub close()
            gworkbook.close()
            gworksheet = nothing
            gworkbook = nothing
            gexcelapplication.displayalerts = true
            gexcelapplication.quit()
            gexcelapplication = nothing
        end sub

        public function query(byval address as string) as datatable
            dim mdatatable as datatable = getdatatable()

            gworksheet.cells.clear()

            gquerytable = gworksheet.querytables.add( _
                connection:=string.format("url;{0}", address), _
                destination:=gworksheet.range("a1"))

            with gquerytable
                .webtables = netconst.webtable_index  这是固定的
                .refresh(backgroundquery:=false)
            end with

            dim mcell as object
            dim mmaxrowindex as integer
            dim line as object

            mmaxrowindex = gworksheet.cells.specialcells(11).row excel.xlcelltype.xlcelltypelastcell=11
            mcell = gworksheet.range("a1")

            for i as integer = 0 to mmaxrowindex
                line = mcell.offset(i, 0).value
                if line isnot nothing then
                    addrow(mdatatable, line.tostring)
                end if
            next

            gquerytable.delete()
            gquerytable = nothing

            return mdatatable
        end function

        private sub addrow(byval table as datatable, byval line as string)
            line = line.trim
            if line.length < 7 then exit sub

            dim tmpcode as string
            dim tmpname as string

            tmpcode = line.substring(0, 6)
            tmpname = line.substring(6).trim

            if not isnumeric(tmpcode) then exit sub 前六位需是数字

            table.rows.add(new string() {tmpcode, tmpname})
        end sub

        private function getdatatable() as datatable
            表的列名意义为：代码、名称
            dim mdatatable as new datatable("regionalcode")
            with mdatatable.columns
                .add("code")
                .add("name")
            end with
            return mdatatable
        end function

    end class
end namespace

测试代码：
mainform.vb(界面部分省，在最后有整个方案供下载)

public class mainform
    private gnetinformation as new regionalcodelibrary.net.netinformation
    private gquerytable as regionalcodelibrary.net.excelquerytable

    private sub button1_click(byval sender as system.object, byval e as system.eventargs) handles button1.click

        if not checknetworkisavailable() then exit sub

        showmessage("正在下载数据信息

")

        gnetinformation.downloadinformationsfromnet()
        with me.combobox1
            .datasource = gnetinformation.updateinformationstable
            .displaymember = "lastdate"
        end with

        showmessage("")
    end sub

    private sub button2_click(byval sender as system.object, byval e as system.eventargs) handles button2.click
        if string.isnullorempty(me.combobox1.text) then exit sub

        if not checknetworkisavailable() then exit sub

        if gquerytable is nothing then

            showmessage("正在启动excel

")
            gquerytable = new regionalcodelibrary.net.excelquerytable

        end if

        dim maddress as string = ctype(me.combobox1.selecteditem, datarowview).row.item("address").tostring

        showmessage(string.format("正在下载{0}数据

", me.combobox1.text))
        me.datagridview1.datasource = gquerytable.query(maddress)

        showmessage(string.format("{0}共有数据{1}项", me.combobox1.text, me.datagridview1.rowcount))
    end sub

    private sub button3_click(byval sender as system.object, byval e as system.eventargs) handles button3.click
        clearenvironment()
    end sub

    private function checknetworkisavailable() as boolean
        dim mresult as boolean = false
        mresult = my.computer.network.isavailable

        if not mresult then
            showmessage("本地连接无效")

        else
            try
                mresult = my.computer.network.ping(regionalcodelibrary.net.netconst.gov_default)
            catch ex as exception
                mresult = false
            end try

            if not mresult then
                showmessage(string.format("本机没有连接internet或发布网址{0}无效", regionalcodelibrary.net.netconst.gov_address))
            end if
        end if

        return mresult
    end function

    private sub showmessage(byval msg as string)
        if msg = "" then msg = "待命"
        me.label1.text = string.format("消息:{0}", msg)
        me.label1.refresh()
    end sub

    private sub mainform_formclosing(byval sender as object, byval e as system.windows.forms.formclosingeventargs) handles me.formclosing
        clearenvironment()
    end sub

    private sub clearenvironment()
        if gquerytable is nothing then exit sub
        gquerytable.close()
        gquerytable = nothing
    end sub
end class