如何在排序后始终将 DataGrid 的一行或多行保持在顶部
本文关键字:一行 顶部 排序 DataGrid | 更新日期: 2023-09-27 17:55:21
我有一个 DataGrid(在视图上)绑定到一个 ObservableCollection(在视图模型上)。
对于这个 ObservableCollection,我以编程方式添加一个"魔术行",因为所选项目将用于对其他地方的另一个集合进行排序,我添加此虚拟行以"清除"过滤。
目前,当视图加载时,我的魔术字符串总是出现在顶部(因为我将其插入索引 0
),但是一旦我单击标题更改排序顺序,行就会按字母顺序重新排列,我的魔术行就消失在瓦砾中。
想要的是魔术行始终显示在顶部,即使我单击标题以更改排序顺序也是如此。
视图模型:
// (...)
public ObservableCollection<FilteringItem> ItemTypes
{
get
{
var result = new ObservableCollection<FilteringItem>(_setups.Select(n => n.ItemType)
.Distinct()
.Select(s => new FilteringItem(s, s))
.OrderBy(v => v.Name));
// Magic Happens Here: adding a "magic" row to remove filtering
// (that is, "allow all") when used by some filtering method elsewhere;
string allString = String.Format("All ({0})", result.Count);
var filteringAll = new FilteringItem(allString, "");
result.Insert(0, filteringAll);
return result;
}
}
// (...)
public class FilteringItem
{
public string Name { get; private set; }
public string Value { get; private set; }
public FilteringItem(string name, string val)
{
Name = name;
Value = val;
}
}
视图:
<DataGrid ItemsSource="{Binding ItemTypes}">
<DataGrid.Columns>
<DataGridTextColumn Header="Tipo" Width="*" Binding="{Binding Name}"/>
</DataGrid.Columns>
</DataGrid>
多
亏了这篇博文,我让它工作了。
"秘密"是截获Sorting
事件(将e.Handled
设置为true
),然后将 DataGrid.ItemsSource 强制转换为ListCollectionView
,然后将自定义IComparer
分配给ListCollectionView.CustomSort
属性。
然后,在排序时,您以某种方式识别您的固定行(在我的情况下,通过 null 值),并使其始终位于顶部(这反过来又取决于ListSortDirection
)。
public partial class ViewContainingDataGrid : UserControl
{
public ViewContainingDataGrid()
{
this.InitializeComponent();
}
private void datagrid_Sorting(object sender, DataGridSortingEventArgs e)
{
e.Handled = true;
SmartSort(sender, e.Column);
}
private void SmartSort(object sender, DataGridColumn column)
{
ListSortDirection direction = (column.SortDirection != ListSortDirection.Ascending) ?
ListSortDirection.Ascending : ListSortDirection.Descending;
column.SortDirection = direction;
var dg = sender as DataGrid;
var lcv = (ListCollectionView)CollectionViewSource.GetDefaultView(dg.ItemsSource);
lcv.CustomSort = new SmartSorter(direction);
}
}
public class SmartSorter : IComparer
{
public ListSortDirection Direction { get; private set; }
public SmartSorter(ListSortDirection direction)
{
Direction = direction;
}
public int Compare(object x, object y)
{
string valorx = x as string;
string valory = y as string;
int comparison = valorx.CompareTo(valory);
if (Direction == ListSortDirection.Descending)
comparison *= -1;
// Override the sorting altogether when you find the special row value
if (String.IsNullOrWhiteSpace(valorx))
comparison = -1;
else
if (String.IsNullOrWhiteSpace(valory))
comparison = 1;
return comparison;
}
}