[摘要]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...
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 datagrid's 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" />
<Columns>
<asp:ButtonColumn Text="Details" HeaderText="FAQ Details" CommandName="details" ButtonType="PushButton" />
<asp:BoundColumn DataField="FAQID" HeaderText="FAQ ID" />
<asp:BoundColumn DataField="Description" HeaderText="FAQ Description" />
</Columns>
</asp:datagrid>
</form>
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:
<script language="vb" runat="server">
Sub Page_Load(sender as Object, e as EventArgs)
If Not Page.IsPostBack then
BindData() 'Only bind the data on the first page load
End If
End Sub
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>
<form runat="server">
<asp:DataGrid runat="server" id="dgFAQDetails" ... >
...
</asp:datagrid>
<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
Author's 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
<% @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 datagrid's 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 datagrid's 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>
<form runat="server">
<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" />
<Columns>
<asp:BoundColumn DataField="CatName" HeaderText="Category Name" />
<asp:BoundColumn DataField="Description" HeaderText="FAQ Description" />
<asp:BoundColumn DataField="ViewCount" DataFormatString="{0:#,###}"
HeaderText="Views" ItemStyle-HorizontalAlign="Center" />
<asp:BoundColumn DataField="SubmittedByName" HeaderText="Author" />
<asp:BoundColumn DataField="SubmittedByEmail" HeaderText="Author's Email" />
<asp:BoundColumn DataField="DateEntered" HeaderText="Date Added"
DataFormatString="{0:MM-dd-yyyy}" />
</Columns>
</asp:datagrid>
<p>
<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" />
<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>
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！
……