我给出第二个答案，因为我最初误解了这个问题。
实现了一个代理来监视集合元素的指定属性。
如果它们的值发生变化，或者集合发生变化，则所有新值都将传递给 Values 属性。
using System;
using System.Globalization;
using System.Windows.Data;
using System.Windows.Markup;
namespace Converters
{
[ValueConversion(typeof(object), typeof(object[]))]
public class ToArrayConverter : IValueConverter, IMultiValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
=> new object[] { value };
public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
{
return values?.Clone();
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
public static ToArrayConverter Instance { get; } = new ToArrayConverter();
}
public class ToArrayConverterExtension : MarkupExtension
{
public override object ProvideValue(IServiceProvider serviceProvider)
=> ToArrayConverter.Instance;
}
}
using Converters;
using System;
using System.Collections;
using System.Collections.Generic;
using System.Windows;
using System.Windows.Data;
namespace Proxy
{
public class ObservingСollectionItemsProxy : Freezable
{
/// <summary>
/// Indexed collection. Items in this collection will be observabled.
/// </summary>
public IList List
{
get { return (IList)GetValue(ListProperty); }
set { SetValue(ListProperty, value); }
}
/// <summary><see cref="DependencyProperty"/> for property <see cref="List"/>.</summary>
public static readonly DependencyProperty ListProperty =
DependencyProperty.Register(nameof(List), typeof(IList), typeof(ObservingСollectionItemsProxy), new PropertyMetadata(null));
/// <summary>
/// The path to the property of the element, the value of which will be passed to the array of values.
/// </summary>
public string ValuePath
{
get { return (string)GetValue(ValuePathProperty); }
set { SetValue(ValuePathProperty, value); }
}
/// <summary><see cref="DependencyProperty"/> for property <see cref="ValuePath"/>.</summary>
public static readonly DependencyProperty ValuePathProperty =
DependencyProperty.Register(nameof(ValuePath), typeof(string), typeof(ObservingСollectionItemsProxy), new PropertyMetadata(null, PathChanged));
private string privatePath;
private static void PathChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
ObservingСollectionItemsProxy proxy = (ObservingСollectionItemsProxy)d;
proxy.privatePath = (string)e.NewValue;
proxy.PathOrCountChanged();
}
/// <summary>
/// An array of observed values.
/// </summary>
public IReadOnlyList<object> Values
{
get { return (IReadOnlyList<object>)GetValue(ValuesProperty); }
private set { SetValue(ValuesPropertyKey, value); }
}
private static readonly IReadOnlyList<object> emptyArray = new object[0];
private static readonly DependencyPropertyKey ValuesPropertyKey =
DependencyProperty.RegisterReadOnly(nameof(Values), typeof(IReadOnlyList<object>), typeof(ObservingСollectionItemsProxy), new PropertyMetadata(emptyArray));
/// <summary><see cref="DependencyProperty"/> for property <see cref="Values"/>.</summary>
public static readonly DependencyProperty ValuesProperty = ValuesPropertyKey.DependencyProperty;
/// <summary>Private property for creating binding to collection items.</summary>
private static readonly DependencyProperty PrivateArrayProperty =
DependencyProperty.Register("1", typeof(object[]), typeof(ObservingСollectionItemsProxy), new PropertyMetadata(null, ArrayChanged));
private static void ArrayChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
((ObservingСollectionItemsProxy)d).Values = (!(e.NewValue is object[] array) || array.Length == 0)
? emptyArray
: Array.AsReadOnly(array);
}
/// <summary>A private property to monitor the number of items in the collection.</summary>
private static readonly DependencyProperty PrivateCountProperty =
DependencyProperty.Register("2", typeof(int?), typeof(ObservingСollectionItemsProxy), new PropertyMetadata(null, CountChanged));
private int? privateCount;
private static void CountChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
ObservingСollectionItemsProxy proxy = (ObservingСollectionItemsProxy)d;
proxy.privateCount = (int?)e.NewValue;
proxy.PathOrCountChanged();
}
private void PathOrCountChanged()
{
MultiBinding multiBinding = new MultiBinding() { Converter = ToArrayConverter.Instance };
if (privateCount != null && privateCount > 0)
{
string path = string.IsNullOrWhiteSpace(privatePath)
? string.Empty
: $".{privatePath.Trim()}";
for (int i = 0; i < privateCount.Value; i++)
{
Binding binding = new Binding($"{nameof(List)}[{i}]{path}")
{
Source = this
};
multiBinding.Bindings.Add(binding);
}
}
BindingOperations.SetBinding(this, PrivateArrayProperty, multiBinding);
}
public ObservingСollectionItemsProxy()
{
Binding binding = new Binding($"{nameof(List)}.{nameof(List.Count)}")
{
Source = this
};
_ = BindingOperations.SetBinding(this, PrivateCountProperty, binding);
}
protected override Freezable CreateInstanceCore()
{
throw new NotImplementedException();
}
}
}
要处理生成的值集合，您可以使用转换器
在处理值的函数的参数中接收委托的转换器示例。
对于此任务，为了让转换器处理值，委托参数必须与 IReadOnlyList<object> 兼容。
也就是说，可以有以下类型中的一种：IReadOnlyCollection<object>、IEnumerable<object>、IEnumerable。
using System;
using System.Globalization;
using System.Reflection;
using System.Windows;
using System.Windows.Data;
using System.Windows.Markup;
namespace Converters
{
public class FuncForValueConverter : IValueConverter
{
public static FuncForValueConverter Instance { get; } = new FuncForValueConverter();
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
if (parameter is Delegate func)
{
MethodInfo method = func.Method;
Type retType = method.ReturnType;
if (retType != null && retType != typeof(void))
{
ParameterInfo[] parameters = method.GetParameters();
if (parameters.Length == 1)
{
try
{
return func.DynamicInvoke(new object[] { value });
}
catch (Exception)
{ }
}
}
}
return DependencyProperty.UnsetValue;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}
public class FuncForValueConverterExtension : MarkupExtension
{
public override object ProvideValue(IServiceProvider serviceProvider)
=> FuncForValueConverter.Instance;
}
}
用法示例。
Helper 类：集合项类型、集合类型、函数集。
using Simplified;
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
namespace ItemsProxyTest
{
public class DoubleItem : BaseInpc
{
private double _number;
public double Number { get => _number; set => Set(ref _number, value); }
}
public static class Function
{
public static readonly Func<IReadOnlyList<object>, double> Average
= (arr) => arr
.OfType<double>()
.Average();
public static readonly Func<IReadOnlyList<object>, double> Sum
= (arr) => arr
.OfType<double>()
.Sum();
}
public class DoubleItemCollection : ObservableCollection<DoubleItem>
{ }
}
XAML：
<Window x:Class="ItemsProxyTest.ItemsProxyTestWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:ItemsProxyTest"
xmlns:proxy="clr-namespace:Proxy;assembly=Common"
xmlns:sys="clr-namespace:System;assembly=mscorlib"
xmlns:cnv="clr-namespace:Converters;assembly=Common"
mc:Ignorable="d"
Title="ItemsProxyTestWindow" Height="450" Width="800">
<FrameworkElement.Resources>
<local:DoubleItemCollection x:Key="list">
<local:DoubleItem Number="123"/>
<local:DoubleItem Number="456"/>
<local:DoubleItem Number="789"/>
</local:DoubleItemCollection>
</FrameworkElement.Resources>
<Grid>
<DataGrid ItemsSource="{DynamicResource list}"
AutoGenerateColumns="False">
<DataGrid.Columns>
<DataGridTextColumn Binding="{Binding Number}">
<DataGridColumn.HeaderTemplate>
<DataTemplate>
<StackPanel>
<FrameworkElement.Resources>
<proxy:ObservingСollectionItemsProxy
x:Key="proxy"
List="{DynamicResource list}"
ValuePath="Number"/>
<sys:String x:Key="str">121321</sys:String>
</FrameworkElement.Resources>
<TextBlock Text="{Binding Values,
Source={StaticResource proxy},
Converter={cnv:FuncForValueConverter},
ConverterParameter={x:Static local:Function.Average}}"/>
<TextBlock Text="{Binding Values,
Source={StaticResource proxy},
Converter={cnv:FuncForValueConverter},
ConverterParameter={x:Static local:Function.Sum}}"/>
</StackPanel>
</DataTemplate>
</DataGridColumn.HeaderTemplate>
</DataGridTextColumn>
</DataGrid.Columns>
</DataGrid>
</Grid>
</Window>