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<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">过滤器不仅可以用于可视化的行，还可以用于这些行中列的状态。在进行</span><span lang="EN-US">ModifiedOriginal </span><span style="FONT-FAMILY: 宋体">或</span><span lang="EN-US"> ModifiedCurrent</span><span style="FONT-FAMILY: 宋体">选择时，这是很明显的。这两个状态都在第</span><span lang="EN-US">21</span><span style="FONT-FAMILY: 宋体">章介绍过了，它们都是基于</span><span lang="EN-US">DataRowVersion</span><span style="FONT-FAMILY: 宋体">枚举的。例如，如果用户更新了数据行中的一列，该行就会在选择</span><span lang="EN-US">ModifiedOriginal</span><span style="FONT-FAMILY: 宋体">或</span><span lang="EN-US"> ModifiedCurrent</span><span style="FONT-FAMILY: 宋体">时显示出来，但其实际值可以是从数据库中选择出来的初值</span><span lang="EN-US">(</span><span style="FONT-FAMILY: 宋体">如果选择了</span><span lang="EN-US">ModifiedOriginal)</span><span style="FONT-FAMILY: 宋体">，或者</span><span lang="EN-US">DataColumn</span><span style="FONT-FAMILY: 宋体">中的当前值</span><span lang="EN-US">(</span><span style="FONT-FAMILY: 宋体">如果选择了</span><span lang="EN-US">ModifiedCurrent)</span><span style="FONT-FAMILY: 宋体">。</span></p>
<p class="MsoNormal"><span lang="EN-US">(3) </span><span style="FONT-FAMILY: 宋体">对数据行进行排序</span></p>
<p class="MsoNormal"><a ftel="sorting"><span style="FONT-FAMILY: 宋体">除了过滤数据外，有时还需要对</span><span lang="EN-US">DataView</span></a><span style="FONT-FAMILY: 宋体">中的数据进行排序。可以在</span><span lang="EN-US">DataGrid</span><span style="FONT-FAMILY: 宋体">控件中单击列标题，这会按照升序或降序的顺序对该列进行排序，如图</span><span lang="EN-US">22-6</span><span style="FONT-FAMILY: 宋体">所示。惟一的问题是控件只能对一列进行排序，而底层的</span><span lang="EN-US">DataView</span><span style="FONT-FAMILY: 宋体">可以对多个列进行排序。</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">在对数据列进行排序时，可以单击列的标题</span><span lang="EN-US">(</span><span style="FONT-FAMILY: 宋体">例如上面的</span><span lang="EN-US">ProductName</span><span style="FONT-FAMILY: 宋体">列</span><span lang="EN-US">)</span><span style="FONT-FAMILY: 宋体">，也可以通过代码排序，</span><span lang="EN-US">DataGrid</span><span style="FONT-FAMILY: 宋体">会显示一个箭头位图，表示对哪一列进行排序。</span></p>
<p align="center"><span lang="EN-US"><img height="189" src="22/image006.jpg" width="320" alt="" /></span></p>
<p style="FTEL: 8.15pt" align="center"><span style="FONT-FAMILY: 宋体">图</span><span lang="EN-US"> 22-6</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">要编程设置列的排列顺序，可以使用</span><span lang="EN-US">DataView</span><span style="FONT-FAMILY: 宋体">的</span><span lang="EN-US">Sort</span><span style="FONT-FAMILY: 宋体">属性：</span></p>
<p class="2" style="MARGIN-TOP: 8.15pt; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US">dataView.Sort = "ProductName";</span></p>
<p class="2" style="MARGIN-TOP: 0cm; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US">dataView.Sort = "ProductName ASC, ProductID DESC"; </span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">上面的第一行按照</span><span lang="EN-US">ProductName</span><span style="FONT-FAMILY: 宋体">列对数据排序，如图</span><span lang="EN-US">22-6</span><span style="FONT-FAMILY: 宋体">所示。第二行按照</span><span lang="EN-US">ProductName</span><span style="FONT-FAMILY: 宋体">列对数据进行升序排序，再以</span><span lang="EN-US">ProductID</span><span style="FONT-FAMILY: 宋体">的降序来排序。</span></p>
<p class="MsoNormal"><span lang="EN-US">DataView</span><span style="FONT-FAMILY: 宋体">支持对列进行升序或降序排序<span style="LETTER-SPACING: -1pt">——</span></span><span lang="EN-US" style="LETTER-SPACING: -1pt"> </span><span style="FONT-FAMILY: 宋体">默认为升序。如果选择对</span><span lang="EN-US">DataView</span><span style="FONT-FAMILY: 宋体">中的多个列进行排序，</span><span lang="EN-US">DataGrid</span><span style="FONT-FAMILY: 宋体">就不会显示任何排序箭头。</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">网格中的每一列都是强类型化的，其排序顺序不是基于列的字符串表示，而是基于实际的数据。如果</span><span lang="EN-US">DataGrid</span><span style="FONT-FAMILY: 宋体">有一个日期列，要对它进行排序，网格就会按日期来进行排序，而不是按日期字符串来进行排序。</span></p>
<h4 style="FTEL: 21.45pt"><span lang="EN-US">4. </span><span style="FONT-FAMILY: 黑体">显示</span><span lang="EN-US">DataSet</span><span style="FONT-FAMILY: 黑体">类中的数据</span></h4>
<p class="MsoNormal"><a ftel="datasets"><span lang="EN-US">DataGrid</span></a><span style="FONT-FAMILY: 宋体">主要用于显示</span><span lang="EN-US">DataSet</span><span style="FONT-FAMILY: 宋体">中的数据。和以前的示例一样，</span><span lang="EN-US">DataGrid</span><span style="FONT-FAMILY: 宋体">一次只能显示一个</span><span lang="EN-US">DataTable</span><span style="FONT-FAMILY: 宋体">，但在下面的示例</span><span lang="EN-US">DataSourceDataSet</span><span style="FONT-FAMILY: 宋体">中，可以浏览</span><span lang="EN-US">DataSet</span><span style="FONT-FAMILY: 宋体">中的关系。下面的代码可以根据</span><span lang="EN-US">Northwind</span><span style="FONT-FAMILY: 宋体">数据库中的</span><span lang="EN-US">Customers</span><span style="FONT-FAMILY: 宋体">和</span><span lang="EN-US">Orders</span><span style="FONT-FAMILY: 宋体">表生成这样一个</span><span lang="EN-US">DataTable</span><span style="FONT-FAMILY: 宋体">。这个示例从两个</span><span lang="EN-US">DataTable</span><span style="FONT-FAMILY: 宋体">中加载数据，然后在这些表之间创建了一个关系</span><span lang="EN-US">CustomerOrders</span><span style="FONT-FAMILY: 宋体">：</span></p>
<p class="2" style="MARGIN-TOP: 8.15pt; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US">string source ="server=(local)\\NetSDK;" + </span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> "uid=QSUser;pwd=QSPassword;" + </span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> "database=northwind";</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">string orders = "SELECT * FROM Orders";</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">string customers = "SELECT * FROM Customers";</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">SqlConnection conn = new SqlConnection(source);</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">SqlDataAdapter da = new SqlDataAdapter(orders, conn);</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">DataSet ds = new DataSet();</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">da.Fill(ds, "Orders");</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">da = new SqlDataAdapter(customers , conn);</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">da.Fill(ds, "Customers");</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">ds.Relations.Add("CustomerOrders",</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> ds.Tables["Customers"].Columns["CustomerID"],</span></p>
<p class="2" style="MARGIN-TOP: 0cm; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US"> ds.Tables["Orders"].Columns["CustomerID"]);</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">创建好后，通过调用</span><span lang="EN-US">SetDataBinding</span><span style="FONT-FAMILY: 宋体">，就可以把</span><span lang="EN-US">DataSet</span><span style="FONT-FAMILY: 宋体">绑定到</span><span lang="EN-US">DataGrid</span><span style="FONT-FAMILY: 宋体">上：</span></p>
<p class="2" style="MARGIN-TOP: 8.15pt; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US">dataGrid1.SetDataBinding(ds, "Customers");</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">这样会得到如</span><span lang="EN-US">22-7</span><span style="FONT-FAMILY: 宋体">所示的屏幕图。</span></p>
<p align="center"><span lang="EN-US"><img height="193" src="22/image007.jpg" width="320" alt="" /></span></p>
<p style="FTEL: 8.15pt" align="center"><span style="FONT-FAMILY: 宋体">图</span><span lang="EN-US"> 22-7</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">注意，与本章前面的</span><span lang="EN-US">DataGrid</span><span style="FONT-FAMILY: 宋体">不同，每个记录的左边都有一个＋号，这表示</span><span lang="EN-US">DataSet</span><span style="FONT-FAMILY: 宋体">在</span><span lang="EN-US">customers </span><span style="FONT-FAMILY: 宋体">和</span><span lang="EN-US">orders</span><span style="FONT-FAMILY: 宋体">表之间有一个可导航的关系。在代码中可以定义许多这类关系。</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">单击</span><span lang="EN-US">+</span><span style="FONT-FAMILY: 宋体">号，就会显示关系列表</span><span lang="EN-US">(</span><span style="FONT-FAMILY: 宋体">如果关系已经显示出来，单击</span><span lang="EN-US">+</span><span style="FONT-FAMILY: 宋体">号就会隐藏该关系</span><span lang="EN-US">)</span><span style="FONT-FAMILY: 宋体">。单击关系名，就可以定位到链接的记录上，如图</span><span lang="EN-US">22-8</span><span style="FONT-FAMILY: 宋体">所示，在本例中是列出选中客户的所有订单。</span></p>
<p align="center"><span lang="EN-US"><img height="194" src="22/image008.jpg" width="320" alt="" /></span></p>
<p style="FTEL: 8.15pt" align="center"><span style="FONT-FAMILY: 宋体">图</span><span lang="EN-GB"> 22-8</span></p>
<p class="MsoNormal"><span lang="EN-US">DataGrid</span><span style="FONT-FAMILY: 宋体">控件的右上角还包含两个新图标。箭头允许用户可以导航回父行，显示上一页的内容。标题行显示父记录的细节，单击另一个按钮会隐藏或显示该箭头。</span></p>
<p class="a3" style="MARGIN-TOP: 8.15pt; FTEL: 21.45pt"><span style="FONT-FAMILY: 黑体">在</span><span lang="EN-US">DataViewManager</span><span style="FONT-FAMILY: 黑体">中显示数据</span></p>
<p class="MsoNormal"><span lang="EN-US">DataViewManager</span><span style="FONT-FAMILY: 宋体">中显示的数据与</span><span lang="EN-US">DataSet</span><span style="FONT-FAMILY: 宋体">中显示的数据相同，但在为</span><span lang="EN-US">DataSet</span><span style="FONT-FAMILY: 宋体">创建</span><span lang="EN-US">DataViewManager</span><span style="FONT-FAMILY: 宋体">时，会为每个</span><span lang="EN-US">DataTable</span><span style="FONT-FAMILY: 宋体">创建一个单独的</span><span lang="EN-US"> DataView</span><span style="FONT-FAMILY: 宋体">，根据过滤条件或者行的状态改变显示出来的行，如上面的</span><span lang="EN-US">DataView</span><span style="FONT-FAMILY: 宋体">示例所示。即使不希望过滤数据，也可以把</span><span lang="EN-US">DataSet</span><span style="FONT-FAMILY: 宋体">包装到</span><span lang="EN-US"> DataViewManager</span><span style="FONT-FAMILY: 宋体">中，以进行显示，因为这样在修改源代码时可以使用更多的选项。</span></p>
<p class="MsoNormal"><a ftel="DataViewManager"><span style="FONT-FAMILY: 宋体">下面的示例根据上一例中的</span><span lang="EN-US">DataSet </span></a><span style="FONT-FAMILY: 宋体">创建一个</span><span lang="EN-US">DataViewManager</span><span style="FONT-FAMILY: 宋体">，然后改变</span><span lang="EN-US">Customers</span><span style="FONT-FAMILY: 宋体">表中的</span><span lang="EN-US">DataView</span><span style="FONT-FAMILY: 宋体">，使之只显示来自英国的客户：</span></p>
<p class="2" style="MARGIN-TOP: 8.15pt; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US">DataViewManager dvm = new DataViewManager(ds);</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">dvm.DataViewSettings["Customers"].RowFilter = "Country='UK'";</span></p>
<p class="2" style="MARGIN-TOP: 0cm; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US">dataGrid.SetDataBinding(dvm, "Customers");</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">如图</span><span lang="EN-US">22-9</span><span style="FONT-FAMILY: 宋体">所示为</span><span class="codeintext-PRODUCTION"><span lang="EN-US" style="FONT-FAMILY: 'Times New Roman'">DataSourceDataViewManager</span></span><span class="codeintext-PRODUCTION"><span style="FONT-FAMILY: 宋体">示</span></span><span style="FONT-FAMILY: 宋体">例代码的运行结果。</span></p>
<p align="center"><span lang="EN-US"><img height="185" src="22/image009.jpg" width="307" alt="" /></span></p>
<p style="FTEL: 8.15pt" align="center"><span style="FONT-FAMILY: 宋体">图</span><span lang="EN-US"> 22-9</span></p>
<h4 style="FTEL: 21.45pt"><span lang="EN-US">5. IListSource</span><span style="FONT-FAMILY: 黑体">和</span><span lang="EN-US"> IList</span><span style="FONT-FAMILY: 黑体">接口</span></h4>
<p class="MsoNormal"><a ftel="IList"><span lang="EN-US">DataGrid</span></a><span style="FONT-FAMILY: 宋体">还支持执行</span><span lang="EN-US">IListSource</span><span style="FONT-FAMILY: 宋体">和</span><span lang="EN-US">IList</span><span style="FONT-FAMILY: 宋体">接口之一的所有对象。</span><span lang="EN-US">IListSource</span><span style="FONT-FAMILY: 宋体">只有一个方法</span><span lang="EN-US">GetList()</span><span style="FONT-FAMILY: 宋体">，它返回一个</span><span lang="EN-US">IList</span><span style="FONT-FAMILY: 宋体">接口，而</span><span lang="EN-US">IList</span><span style="FONT-FAMILY: 宋体">比较有趣，它可由运行库中的许多类执行，执行这个接口的类有</span><span lang="EN-US">Array</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US">ArrayList</span><span style="FONT-FAMILY: 宋体">和</span><span lang="EN-US">StringCollection</span><span style="FONT-FAMILY: 宋体">。</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">在使用</span><span lang="EN-US">IList</span><span style="FONT-FAMILY: 宋体">时，对前面</span><span lang="EN-US">Array</span><span style="FONT-FAMILY: 宋体">的警告也适用于集合中的对象<span style="LETTER-SPACING: -1pt">——</span></span><span style="LETTER-SPACING: -1pt"> </span><span style="FONT-FAMILY: 宋体">如果使用</span><span lang="EN-US">StringCollection</span><span style="FONT-FAMILY: 宋体">作为</span><span lang="EN-US">DataGrid</span><span style="FONT-FAMILY: 宋体">的数据源，网格中就会显示字符串的长度，而不是我们希望显示的元素文本。</span></p></div>
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