我正在使用数据网格为学生记录创建一个 C# wpf 应用程序。 如何在标题中创建复选框以选择/取消选择一行中的所有复选框？ 如何一键选中行中的复选框以便我们可以编辑/删除记录？我们如何选择多个复选框来删除？
最佳答案
我创建了一种行为，允许将控件中的属性绑定(bind)到项目集合的属性，方式如下:
- 如果更改控件中的属性，所有项目都会更新。
- 如果更改项目中的属性，如果所有项目都具有相同的属性，则控件将反射(reflect)它。如果没有，控件的属性将被赋予一个后备值(如 null)。
通过此行为，您可以向 DataGrid header 添加一个复选框，并将其 IsChecked 属性绑定(bind)到 DataGrid 的 ItemSource，即集合类型的属性。
我们可以使用 MVVM 模式来处理选择逻辑。例如，我们有以下集合实体的 ViewModel:
public class ItemViewModel : INotifyPropertyChanged
{
#region INotifyPropertyChanged
public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged(string propertyName)
{
if (this.PropertyChanged != null)
{
this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
#endregion
private bool isSelected;
public bool IsSelected {
get { return this.isSelected; }
set
{
if (this.isSelected == value)
return;
this.isSelected = value;
this.OnPropertyChanged("IsSelected");
}
}
private string myProperty;
public string MyProperty
{
get { return this.myProperty; }
set
{
if (this.myProperty != value)
{
this.myProperty = value;
this.OnPropertyChanged("MyProperty");
}
}
}
}
然后我们有 MainViewModel，它控制 MainWindow 的逻辑:
public class MainViewModel: INotifyPropertyChanged
{
#region INotifyPropertyChanged
public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged(string propertyName)
{
if (this.PropertyChanged != null)
{
this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
#endregion
#region Items (INotifyPropertyChanged Property)
private ObservableCollection<ItemViewModel> items;
public ObservableCollection<ItemViewModel> Items
{
get { return this.items; }
set
{
if (this.items != value)
{
this.items = value;
this.OnPropertyChanged("Items");
}
}
}
#endregion
public MainViewModel()
{
this.Items = new ObservableCollection<ItemViewModel>();
for (int i = 0; i < 10; i++)
this.Items.Add(new ItemViewModel() { MyProperty = "Item" + i });
}
}
在我们的窗口中，我们可以声明 DataGrid。为了实现您想要的，我们必须做到以下几点:
- 将 MainViewModel 分配给 Window.DataContext
- 将 DataGrid.ItemsSource 绑定(bind)到 MainViewModel 中的 Items 属性
- 定义 DataGrid 的列。在示例中，我选择有一个“IsSelected”列，并将“SelectAll”复选框添加到其标题中，如您所指定，但通过这种行为，您可以在任何地方有一个复选框来控制选择。
- 我们需要使行的选择更新项目的“IsSelected”属性，反之亦然。为此，我们修改 RowStyle，以便可以将行的“IsSelected”属性绑定(bind)到其项目的“IsSelected”。这样，选择逻辑现在可以完全由 ViewModel 驱动。
- 最后要做的事情是让“SelectAll”复选框完成其工作。我们应用 CollectionPropertyBehavior 并对其进行配置，使其“SourcePropertyPath”指向我们要绑定(bind)的 CheckBox 中的属性(“IsChecked”)，并且 CollectionPropertyPath 指向项目中的属性(“IsSelected”)。然后我们只需将其 ItemsSource 绑定(bind)到 DataGridItemsSource 即可。请注意，默认值为“null”，这意味着当项目的属性中具有不同值时，CheckBox 将接收“null”并处于未定义状态。
最终的xaml将是这样的:
<Window xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:local="clr-namespace:WpfApplication2" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity" x:Class="WpfApplication2.MainWindow"
Title="MainWindow" mc:Ignorable="d" Height="350" Width="525">
<Window.Resources>
<Style x:Key="DataGridRowStyle" TargetType="{x:Type DataGridRow}">
<Setter Property="IsSelected" Value="{Binding IsSelected}"/>
</Style>
</Window.Resources>
<Window.DataContext>
<local:MainViewModel/>
</Window.DataContext>
<Grid>
<DataGrid AutoGenerateColumns="False" ItemsSource="{Binding Items}" CanUserAddRows="False" RowStyle="{DynamicResource DataGridRowStyle}">
<DataGrid.Columns>
<DataGridCheckBoxColumn Binding="{Binding IsSelected}">
<DataGridCheckBoxColumn.Header>
<CheckBox>
<i:Interaction.Behaviors>
<local:CollectionPropertyBehavior CollectionPropertyPath="IsSelected" SourcePropertyPath="IsChecked" ItemsSource="{Binding ItemsSource, RelativeSource={RelativeSource AncestorType={x:Type DataGrid}}}"/>
</i:Interaction.Behaviors>
</CheckBox>
</DataGridCheckBoxColumn.Header>
</DataGridCheckBoxColumn>
<DataGridTextColumn Width="*" Binding="{Binding MyProperty}"/>
</DataGrid.Columns>
</DataGrid>
</Grid>
最后，行为:
public class CollectionPropertyBehavior : Behavior<DependencyObject>
{
private IEnumerable<ValueProxy> proxies;
private bool syncking;
public string SourcePropertyPath
{
get { return (string)GetValue(SourcePropertyPathProperty); }
set { SetValue(SourcePropertyPathProperty, value); }
}
public static readonly DependencyProperty SourcePropertyPathProperty =
DependencyProperty.Register("SourcePropertyPath", typeof(string), typeof(CollectionPropertyBehavior), new PropertyMetadata(null));
public string CollectionPropertyPath
{
get { return (string)GetValue(CollectionPropertyPathProperty); }
set { SetValue(CollectionPropertyPathProperty, value); }
}
public static readonly DependencyProperty CollectionPropertyPathProperty =
DependencyProperty.Register("CollectionPropertyPath", typeof(string), typeof(CollectionPropertyBehavior), new PropertyMetadata(null));
private IEnumerable<object> Items { get { return this.ItemsSource == null ? null : this.ItemsSource.OfType<object>(); } }
public IEnumerable ItemsSource
{
get { return (IEnumerable)GetValue(ItemsSourceProperty); }
set { SetValue(ItemsSourceProperty, value); }
}
public static readonly DependencyProperty ItemsSourceProperty =
DependencyProperty.Register("ItemsSource", typeof(IEnumerable), typeof(CollectionPropertyBehavior), new PropertyMetadata(null, ItemsSourceChanged));
private object Value
{
get { return (object)GetValue(ValueProperty); }
set { SetValue(ValueProperty, value); }
}
private static readonly DependencyProperty ValueProperty =
DependencyProperty.Register("Value", typeof(object), typeof(CollectionPropertyBehavior), new PropertyMetadata(null, ValueChanged));
public object DefaultValue
{
get { return (object)GetValue(DefaultValueProperty); }
set { SetValue(DefaultValueProperty, value); }
}
public static readonly DependencyProperty DefaultValueProperty =
DependencyProperty.Register("DefaultValue", typeof(object), typeof(CollectionPropertyBehavior), new PropertyMetadata(null));
private static void ValueChanged(object sender, DependencyPropertyChangedEventArgs args)
{
var element = sender as CollectionPropertyBehavior;
if (element == null || element.ItemsSource == null) return;
element.UpdateCollection();
}
private static void ItemsSourceChanged(object sender, DependencyPropertyChangedEventArgs args)
{
var element = sender as CollectionPropertyBehavior;
if (element == null || element.ItemsSource == null) return;
element.ItemsSourceChanged();
}
private void ItemsSourceChanged()
{
this.proxies = null;
if (this.Items == null || !this.Items.Any() || this.CollectionPropertyPath == null) return;
// Cria os proxies
this.proxies = this.Items.Select(o =>
{
var proxy = new ValueProxy();
proxy.Bind(o, this.CollectionPropertyPath);
proxy.ValueChanged += (s, e) => this.UpdateSource();
return proxy;
}).ToArray();
this.UpdateSource();
}
private void UpdateSource()
{
if (this.syncking) return;
// Atualiza o valor
using (new SynckingScope(this))
{
object value = this.proxies.First().Value;
foreach (var proxy in this.proxies.Skip(1))
{
value = object.Equals(proxy.Value, value) ? value : this.DefaultValue;
}
this.Value = value;
}
}
private void UpdateCollection()
{
// Se o valor estiver mudando em função da atualização de algum
// elemento da coleção, não faz nada
if (this.syncking) return;
using (new SynckingScope(this))
{
// Atualiza todos os elementos da coleção,
// atrávés dos proxies
if (this.proxies != null)
foreach (var proxy in this.proxies)
proxy.Value = this.Value;
}
}
protected override void OnAttached()
{
base.OnAttached();
// Bind da propriedade do objeto fonte para o behavior
var binding = new Binding(this.SourcePropertyPath);
binding.Source = this.AssociatedObject;
binding.Mode = BindingMode.TwoWay;
BindingOperations.SetBinding(this, ValueProperty, binding);
}
protected override void OnDetaching()
{
base.OnDetaching();
// Limpa o binding de value para a propriedade do objeto associado
this.ClearValue(ValueProperty);
}
internal class SynckingScope : IDisposable
{
private readonly CollectionPropertyBehavior parent;
public SynckingScope(CollectionPropertyBehavior parent)
{
this.parent = parent;
this.parent.syncking = true;
}
public void Dispose()
{
this.parent.syncking = false;
}
}
internal class ValueProxy : DependencyObject
{
public event EventHandler ValueChanged;
public object Value
{
get { return (object)GetValue(ValueProperty); }
set { SetValue(ValueProperty, value); }
}
public static readonly DependencyProperty ValueProperty =
DependencyProperty.Register("Value", typeof(object), typeof(ValueProxy), new PropertyMetadata(null, OnValueChanged));
private static void OnValueChanged(object sender, DependencyPropertyChangedEventArgs args)
{
var element = sender as ValueProxy;
if (element == null || element.ValueChanged == null) return;
element.ValueChanged(element, EventArgs.Empty);
}
public void Bind(object source, string path)
{
// Realiza o binding de value com o objeto desejado
var binding = new Binding(path);
binding.Source = source;
binding.Mode = BindingMode.TwoWay;
BindingOperations.SetBinding(this, ValueProperty, binding);
}
}
}
这种方法的优点是它是完全可重用的。在此示例中，我们使用它来处理选择，但您可以将 ItemViewModel 中的枚举属性绑定(bind)到 header 中的 ComboBox 等。
该行为是从我的 Silverlight 4 项目移植的，但经过测试，它在 WPF 应用程序中运行良好。然而，我认为在 WPF 中我们也许可以找到一种更好的方法，使行为适应 MarkupExtension。如果有时间我可能会看一下。此外，我们还可以对其进行调整，以便可以将其绑定(bind)到 SelectedItems，这样当有选定的项目时，它会更新它们，而当没有选定的项目时，它会更新所有项目。
关于c# - Datagrid wpf C# 应用程序中的复选框，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/13540566/