如果字符串是唯一的，为什么不使用ToObservableChangeSet的重载，将字符串设置为键。这样，如果新列表不包含“F”，它就知道应该删除现有的“F”。
也许有一个更简单的方法，但你可能需要临时插入你自己的索引。如果你不需要通过绑定的集合来跟踪更改，你可以从变更集中这样做：

Subject<IReadOnlyList<string>> source = new Subject<IReadOnlyList<string>>();
IObservable<IEnumerable<string>> observableOfList = source;
IObservable<IChangeSet<(string,int),string>> observableOfChangeSet = source.Select(x => 
            {
                return x.Select((item, index) => (item, index));
            }).ToObservableChangeSet<(string,int),string>(x=>x.Item1);

observableOfChangeSet
    .Sort(SortExpressionComparer<(string, int)>.Ascending(x => x.Item2))
    .OnItemAdded(x=> Debug.WriteLine($"Item {x.Item1} was added to index {x.Item2}"))
    .OnItemRemoved(x => Debug.WriteLine($"Item {x.Item1} was removed from index {x.Item2}"))
    .OnItemUpdated((x,prev) => Debug.WriteLine($"Item {prev.Item1} at index {prev.Item2} was updated to Item {x.Item1} at index {x.Item2}"))
    .Transform(x=>
        {
            Debug.WriteLine($"Item: {x.Item1} at index: {x.Item2}");
           return x.Item1;
        })
    .Bind(out ReadOnlyObservableCollection<string> boundCollection)
    .Subscribe();

source.OnNext(new[] { "A", "C", "F" });
source.OnNext(new[] { "A", "B", "C" });

这段代码的调试输出：

Item A was added to index 0
Item C was added to index 1
Item F was added to index 2
Item: A at index: 0
Item: C at index: 1
Item: F at index: 2
Item B was added to index 1
Item F was removed from index 2
Item A at index 0 was updated to Item A at index 0
Item C at index 1 was updated to Item C at index 2
Item: A at index: 0
Item: B at index: 1
Item: C at index: 2

我对DynamicData不是很熟悉，但我相信这会给出一些接近预期结果的东西：

using DynamicData;
using System;
using System.Collections.Generic;
using System.Reactive.Linq;
using System.Reactive.Subjects;

namespace ConsoleApp3
{
    class Program
    {
        static void Main(string[] args)
        {
            Subject<IReadOnlyList<string>> source = new Subject<IReadOnlyList<string>>();

            var list = ObservableChangeSet.Create<string>(sourceList =>
            {
                return source
                    .Subscribe(newItems =>
                    {
                        sourceList.Edit(items =>
                        {
                            for (var i = 0; i < newItems.Count; i++)
                            {
                                if (items.Count <= i) items.Add(newItems[i]);
                                else
                                {
                                    if (items[i] != newItems[i])
                                    {
                                        items[i] = newItems[i];
                                    }
                                }
                            }
                            while (items.Count > items.Count) items.RemoveAt(items.Count - 1);
                        });
                    });
            }).AsObservableList();

            source.OnNext(new[] { "A", "C", "F" });
            source.OnNext(new[] { "A", "B", "C", "F" });
            source.OnNext(new[] { "A", "B", "C" });

            Console.ReadLine();
        }
    }
}

不幸的是，我没有弄清楚如何获得Add "B" at index 1，但当前输出如下：

1. AddRange. 3 changes

• 3 Changes
• Replace. Current: B, Previous: C
• Replace. Current: C, Previous: F
• Add. Current: F, Previous: <None>
• Remove. Current: C, Previous: <None>
  **编辑：**下面给出了你想要的确切输出，但我还没有测试每一个的性能（对于更大的列表，插入可能会变得昂贵）：

using DynamicData;
using System;
using System.Collections.Generic;
using System.Reactive.Linq;
using System.Reactive.Subjects;

namespace ConsoleApp3
{
    class Program
    {
        static void Main(string[] args)
        {
            Subject<IReadOnlyList<string>> source = new Subject<IReadOnlyList<string>>();

            var list = ObservableChangeSet.Create<string>(sourceList =>
            {
                return source
                    .Subscribe(newItems =>
                    {
                        sourceList.Edit(items =>
                        {
                            for (var i = 0; i < newItems.Count; i++)
                            {
                                if (items.Count <= i) items.Add(newItems[i]);
                                else
                                {
                                    if (items[i] != newItems[i])
                                    {
                                        items.Insert(i, newItems[i]);
                                    }
                                }
                            }
                            while (items.Count > newItems.Count) items.RemoveAt(items.Count - 1);
                        });
                    });
            }).AsObservableList();

            source.OnNext(new[] { "A", "C", "F" });
            source.OnNext(new[] { "A", "B", "C", "F" });
            source.OnNext(new[] { "A", "B", "C" });

            Console.ReadLine();
        }
    }
}

1. AddRange. 3 changes
2. Add. Current: B, Previous: <None> Index 1
3. Remove. Current: C, Previous: <None> Index 2

最后我写了一个自定义解决方案。
它是开源的，也提供了nuget包。

• 代码：https://github.com/jeanplevesque/CollectionTracking#collectiontracking
• Package ：https://www.nuget.org/packages/CollectionTracking.DynamicData

要解决原始问题，请安装以下软件包。

• CollectionTracking.DynamicData
• System.Reactive

然后，您可以使用如下方法。

using System.Reactive.Linq;
using CollectionTracking;
// ...
public static class DynamicDataExtensions
{
    /// <summary>
    /// Converts <see cref="IObservable{IEnumerable}"/> to <see cref="IObservableList{T}"/>.
    /// Keeps the same ordering, which is why we use .GetOperations and not .EditDiff.
    /// </summary>
    /// <typeparam name="T">Type of items in list.</typeparam>
    /// <param name="observableOfList"><see cref="IObservable{IEnumerable}"/> to convert.</param>
    /// <returns>Converted <see cref="IObservableList{T}"/>.</returns>
    public static IObservableList<T> ToObservableList<T>(this IObservable<IEnumerable<T>> observableOfList)
    {
        return observableOfList
            .StartWith(Enumerable.Empty<T>())
            .Buffer(2, 1)
            .Select(lists => lists[0].GetOperations(lists[1]).ToChangeSet())
            .AsObservableList();
    }
}