DataGrid Web控件深度历险(3) part3-.NET教程,组件控件开发-IDC资讯中心

在本文第二部分我们研究了如何通过buttoncolumn标记在datagrid中显示按钮。此外，我们考察了如何将事件处理程序与按钮的点击联系起来。下面我们将了解到如何判断datagrid中哪一行的按钮被点击并且基于这些信息执行相应的动作。

判断哪一行的按钮被点击

回想一下点击按钮的事件处理程序定义如下：

sub eventhandlername(sender as object, e as datagridcommandeventargs)

…

end sub

datagridcommandeventargs类包含一个item属性，该属性包含了触发该事件的源对象。item属性是tablerow类的一个实例，它指向datagrid中被点击的那一行。可使用cells属性访问tablerow类中的列。例如有一个datagrid,它的列信息定义如下：

<asp:datagrid runat="server" … >

<columns>

<asp:buttoncolumn text="details" headertext="faq details" commandname="details" />

<asp:boundcolumn datafield="faqid" headertext="faq id" />

<asp:boundcolumn datafield="description" headertext="faq description" />

</columns>

</asp:datagrid>

那么在点击按钮的事件处理程序中，可通过以下方法获得被点击行的某一列的值：

sub detailsclicked(sender as object, e as datagridcommandeventargs)

dim buttoncolumn as tablecell = e.item.cells(0)

dim faqidcolumn as tablecell = e.item.cells(1)

dim desccolumn as tablecell = e.item.cells(2)

dim buttoncoltext as string = buttoncolumn.text

dim faqidcoltext as string = faqidcolumn.text

dim desccoltext as string = desccolumn.text

end sub

示例运行结果如下:

更新按钮事件处理程序后的datagrid示例

本示例展示了一个包含detail按钮的datagrid web控件并演示了当按下按钮时如何触发一段代码。注意点击某个detail按钮后你会看到被点击按钮所在行的信息。

value of clicked button column text:

value of faqid column text: 181

value of clicked description column text: how can i format numbers and date/times using asp.net? for example, i want to format a number as a currency.

faq details

faq id

faq description

144

where can i host my asp web site for free (similar to geocities or tripod or any of the many other free web site sites)?

181

how can i format numbers and date/times using asp.net? for example, i want to format a number as a currency.

…

源代码

<% @import namespace="system.data" %>

<% @import namespace="system.data.sqlclient" %>

<script language="vb" runat="server">

sub page_load(sender as object, e as eventargs)

if not page.ispostback then

binddata()

end if

end sub

sub binddata()

1. create a connection

dim myconnection as new sqlconnection(configurationsettings.appsettings("connectionstring"))

2. create the command object, passing in the sql string

const strsql as string = "sp_popularity"

dim mycommand as new sqlcommand(strsql, myconnection)

set the datagrids datasource to the datareader and databind

myconnection.open()

dgpopularfaqs.datasource = mycommand.executereader(commandbehavior.closeconnection)

dgpopularfaqs.databind()

end sub

sub dispdetails(sender as object, e as datagridcommandeventargs)

dim buttoncolumn as tablecell = e.item.cells(0)

dim faqidcolumn as tablecell = e.item.cells(1)

dim desccolumn as tablecell = e.item.cells(2)

dim buttoncoltext as string = buttoncolumn.text

dim faqidcoltext as string = faqidcolumn.text

dim desccoltext as string = desccolumn.text

lblbct.text = buttoncoltext

lblfct.text = faqidcoltext

lbldct.text = desccoltext

end sub

</script>

<form runat="server">

<b>value of clicked button column text</b>:

<asp:label id="lblbct" runat="server" /><br />

<b>value of faqid column text</b>:

<asp:label id="lblfct" runat="server" /><br />

<b>value of clicked description column text</b>:

<asp:label id="lbldct" runat="server" /><br />

<asp:datagrid runat="server" id="dgpopularfaqs"

backcolor="#eeeeee" width="85%"

horizontalalign="center"

font-name="verdana" cellpadding="4"

font-size="10pt" autogeneratecolumns="false"

onitemcommand="dispdetails">

<headerstyle backcolor="black" forecolor="white" font-bold="true" horizontalalign="center" />

<alternatingitemstyle backcolor="white" />

请仔细检查上面的示例。你可能注意到的第一件事就是按钮列不包含任何文本。这是因为仅需通过html即可显示按钮，因此tablecell的text属性返回了一个空字符串。

在本文开始部分我讲述了一个电子商务公司的场景，该公司希望显示部分货运信息，但同时提供显示所有货运信息的选择。到目前为止的示例中，我们仅显示了sp_popularity存储过程返回列中的一小部分列。想象一下我们仅希望显示最受欢迎的常见问题的描述列，然后提供一个detail按钮允许用户查看某个常见问题的其余信息。

虽然我们不希望在datagrid中显示faqid列，但是我们仍然需要为detialsclicked事件处理程序提供该信息，因为它数据库中表的关键字并唯一标识了每个常见问题。通过对datagrid标记进行小小的改动(在与数据库中faqid列对应的boundcolumn标记中增加visible= "false")，我们仍然能够传递该信息。此改动隐藏了faqid列，但仍然允许detailclicked事件处理程序访问某个常见问题的标识(通过e.item.cells(1).text)。

因此我们所要做的就是改写detailsclicked事件处理程序，以便当它被触发时获得用户希望显示的那个常见问题的信息，然后再显示该常见问题的详细信息。在阅读了一系列关于如何使用datagrid的文章后，当需要显示数据库中的数据时，你的第一个想法应该就是使用datagrid。因此我们的页面看起来应该是这样:

sub binddata()

make a connection to the database

databind the datareader results to the gpopularfaqs datagrid.

end sub

sub detailsclicked(sender as object, e as datagridcommandeventargs)

get detailed information about the selected faq and bind

the database results to the dgfaqdetails datagrid

end sub

</script>

<asp:datagrid runat="server" id="dgpopularfaqs" … >

<columns>

<asp:buttoncolumn text="details" headertext="faq details"

buttontype="pushbutton" />

<asp:boundcolumn datafield="faqid" visible="false" />

<asp:boundcolumn datafield="description" headertext="faq description" />

</columns>

</asp:datagrid>

</form>

示例运行结果如下:

本示例展示了如何在datagrid的每一行中显示概要信息和一个detail按钮，当按钮被点击时，对所选择的数据项显示其余信息。

category name

faq description

views

author

authors email

date added

getting started

where can i host my asp web site for free (similar to geocities or tripod or any of the many other free web site sites)?

163,148

scott mitchell

mitchell@4guysfromrolla.com

03-20-2001

faq details

faq description

where can i host my asp web site for free (similar to geocities or tripod or any of the many other free web site sites)?

…

源代码

sub binddata()

1. create a connection

dim myconnection as new sqlconnection(configurationsettings.appsettings("connectionstring"))

2. create the command object, passing in the sql string

const strsql as string = "sp_popularity"

dim mycommand as new sqlcommand(strsql, myconnection)

set the datagrids datasource to the datareader and databind

myconnection.open()

dgpopularfaqs.datasource = mycommand.executereader(commandbehavior.closeconnection)

dgpopularfaqs.databind()

end sub

sub dispdetails(sender as object, e as datagridcommandeventargs)

dim faqid as integer = convert.toint32(e.item.cells(1).text)

get information about the particular faq

dim myconnection as new sqlconnection(configurationsettings.appsettings("connectionstring"))

2. create the command object, passing in the sql string

dim strsql as string = "spgetfaq"

dim mycommand as new sqlcommand(strsql, myconnection)

mycommand.commandtype = commandtype.storedprocedure

add parameters to sproc

dim parameterfaqid as new sqlparameter("@faqid", sqldbtype.int, 4)

parameterfaqid.value = faqid

mycommand.parameters.add(parameterfaqid)

set the datagrids datasource to the datareader and databind

myconnection.open()

dgfaqdetails.datasource = mycommand.executereader(commandbehavior.closeconnection)

dgfaqdetails.databind()

dgfaqdetails.visible = true make the faq details datagrid visible

end sub

</script>

<asp:datagrid runat="server" id="dgfaqdetails"

backcolor="#eeeeee" width="90%"

horizontalalign="center"

font-name="verdana" cellpadding="4"

font-size="10pt" autogeneratecolumns="false"

visible="false">

<headerstyle backcolor="black" forecolor="white" font-bold="true" horizontalalign="center" />

<alternatingitemstyle backcolor="white" />

需要注意的第一件事就是asp.net web页面中有两个datagrid。第一个(dgfaqdetails)用于显示一个特定常见问题的详细信息。第二个(dgpopularfaqs)是我们一直用来显示最受欢迎的10个常见问题的那个datagrid。注意dgpopularfaqs datagrid的faqid绑定列被修改了，增加了visible="false"，以便faqid列不在dgpopularfaqs datagrid的输出中显示。

在过去的三篇文章中我们研究了将数据库查询的结果显示在html表格中(第一篇)，在无需编写代码的情况下美化html表格(第二篇)和本篇中如何在每列中增加按钮并对事件进行响应。我们将在今后的文章中看到“增加按钮并当按钮被点击时进行响应”的概念可被扩展以允许进行排序、分页和编辑数据。回见……

祝编程愉快！

DataGrid Web控件深度历险(3) part3-.NET教程,组件控件开发

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