我正在使用MVVM模式,我在XAML中为DataGrid的SelectedItem创建了一个绑定。我以编程方式设置SelectedItem,但是当我这样做时,DataGrid不会滚动到选择。有没有办法在不完全打破MVVM模式的情况下实现这一目标?
我找到了以下解决方案但是当我尝试实现Behavior
类时出现错误,即使我已经安装了Blend SDK:http://www.codeproject.com/Tips/125583/ScrollIntoView-for-a-DataGrid-when-using-MVVM
答案 0 :(得分:31)
这应该有效。我们的想法是,您将附加到DataGrid
附加的附加属性。在您附加它的xaml中,您将它绑定到ViewModel
上的属性。每当您想以编程方式为SelectedItem
分配值时,还要为此属性设置一个值,附加属性绑定到该属性。
我已将附加的属性类型设置为SelectedItem
类型的任何类型,但老实说,只要将其设置为与以前不同的类型,类型是什么并不重要。此附加属性仅用作以MVVM友好方式在视图控件(在本例中为DataGrid
)执行某些代码的方法。
那就是说,这是附属物的代码:
namespace MyAttachedProperties
{
public class SelectingItemAttachedProperty
{
public static readonly DependencyProperty SelectingItemProperty = DependencyProperty.RegisterAttached(
"SelectingItem",
typeof(MySelectionType),
typeof(SelectingItemAttachedProperty),
new PropertyMetadata(default(MySelectionType), OnSelectingItemChanged));
public static MySelectionType GetSelectingItem(DependencyObject target)
{
return (MySelectionType)target.GetValue(SelectingItemProperty);
}
public static void SetSelectingItem(DependencyObject target, MySelectionType value)
{
target.SetValue(SelectingItemProperty, value);
}
static void OnSelectingItemChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
{
var grid = sender as DataGrid;
if (grid == null || grid.SelectedItem == null)
return;
// Works with .Net 4.5
grid.Dispatcher.InvokeAsync(() =>
{
grid.UpdateLayout();
grid.ScrollIntoView(grid.SelectedItem, null);
});
// Works with .Net 4.0
grid.Dispatcher.BeginInvoke((Action)(() =>
{
grid.UpdateLayout();
grid.ScrollIntoView(grid.SelectedItem, null);
}));
}
}
}
这是xaml片段:
<Window ...
xmlns:attachedProperties="clr-namespace:MyAttachedProperties">
...
<DataGrid
attachedProperties:SelectingItemAttachedProperty.SelectingItem="{Binding MyViewModel.SelectingItem}">
...
</DataGrid>
</Grid>
答案 1 :(得分:16)
我是MVVM的新手。我理解MVVM的想法,并尝试正确实现一切。 我上面遇到了类似的问题,最后我在XAML中输了1行,后面跟着1行代码。其余代码在VM中。 我在XAML中做了以下
<ListBox DockPanel.Dock="Top"
Name="Selection1List"
ItemsSource="{Binding SelectedList1ItemsSource}"
SelectedItem="{Binding SelectedList1Item}"
SelectedIndex="{Binding SelectedList1SelectedIndex}"
SelectionChanged="Selection1List_SelectionChanged">
这在后面的代码中:
private void Selection1List_SelectionChanged(object sender, SelectionChangedEventArgs e) {
Selection1List.ScrollIntoView(Selection1List.SelectedItem);
}
这很好。
我知道有些人甚至不想在窗口后面的代码中使用一行代码。但我认为这一行只是为了观点。它与数据或数据逻辑无关。所以我认为这不违反MVVM原则 - 而且更容易实现。
欢迎任何评论。
答案 2 :(得分:0)
@Edgar的解决方案工作正常,但是在我的应用程序中,我还必须检查SelectionChangedEventArgs的OriginalSource。
private void OperatorQualificationsTable_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
if ((OperatorQualificationsTable.SelectedItem != null) && (e.OriginalSource?.Equals(OperatorQualificationsTable) ?? false))
{
OperatorQualificationsTable.ScrollIntoView(OperatorQualificationsTable.SelectedItem);
}
}
我的数据网格包含以下ComboBoxColumn
<dgx:EnhancedDataGridComboBoxColumn
DisplayMemberPath="DescriptionNL"
Header="{x:Static nl:Strings.Label_Qualification}"
ItemsSource="{Binding Path=QualificationKeysView, Source={StaticResource ViewModel}}"
SelectedValueBinding="{Binding ActivityQualification.QualificationKey}"
SelectedValuePath="QualificationKey"/>
每次我向上或向下滚动时,组合框都会调用更改选择的事件,并且不再可能将所选项目移出视图。
答案 3 :(得分:0)
这是我使ScrollIntoView
工作的解决方案。我在LayoutUpdated()
事件中执行操作
public void ManipulateData()
{
// Add a new record or what else is needed;
myItemsSourceCollection.Add(...);
// Not needed when the ItemsSource is a ObervableCollectin
// with correct Binding (ItemsSource="{ Binding myItemsSourceElement }")
myDataGrid.Items.Refresh();
// Goto last Item or where ever
myDataGrid.SelectedIndex = this.myDataGrid.Items.Count - 1;
}
// The LayoutUpdated event for the DataGrid
private void myDataGrid_LayoutUpdated(object sender, EventArgs e)
{
if (myDataGrid.SelectedItem == null)
return;
//<----------
// may become improved to check first if the `ScrollIntoView()` is really needed
// To prevent hanging here the ItemsSource must be
// a) an ObervableCollection with a correct working binding or
// b) myDataGrid.Items.Refresh(); must be called after changing
// the data
myDataGrid.ScrollIntoView(myDataGrid.SelectedItem, null);
}