你可以创建一个专门用于此的扩展方法:

public static class EnumerableExtensions {
    public static bool IsLast<T>(this List<T> items, T item)
        {
            if (items.Count == 0)
                return false;
            T last = items[items.Count - 1];
            return item.Equals(last);
        }
    }

你可以这样使用它:

foreach (Item result in Model.Results)
{
    if(Model.Results.IsLast(result))
    {
        //do something in the code
    }
}

根据@Shimmy的回复，我创建了一个扩展方法，这是每个人都想要的解决方案。它很简单，易于使用，并且只循环遍历集合一次。

internal static class EnumerableExtensions
{
    public static void ForEachLast<T>(this IEnumerable<T> collection, Action<T>? actionExceptLast = null, Action<T>? actionOnLast = null)
    {
        using var enumerator = collection.GetEnumerator();
        var isNotLast = enumerator.MoveNext();
        while (isNotLast)
        {
            var current = enumerator.Current;
            isNotLast = enumerator.MoveNext();
            var action = isNotLast ? actionExceptLast : actionOnLast;
            action?.Invoke(current);
        }
    }
}

这适用于任何IEnumerable< t>。用法如下:

var items = new[] {1, 2, 3, 4, 5};
items.ForEachLast(i => Console.WriteLine($"{i},"), i => Console.WriteLine(i));

输出如下:

1,
2,
3,
4,
5

此外，您还可以将其设置为Select样式方法。然后，在ForEach中重用该扩展。代码是这样的:

internal static class EnumerableExtensions
{
    public static void ForEachLast<T>(this IEnumerable<T> collection, Action<T>? actionExceptLast = null, Action<T>? actionOnLast = null) =>
        // ReSharper disable once IteratorMethodResultIsIgnored
        collection.SelectLast(i => { actionExceptLast?.Invoke(i); return true; }, i => { actionOnLast?.Invoke(i); return true; }).ToArray();

    public static IEnumerable<TResult> SelectLast<T, TResult>(this IEnumerable<T> collection, Func<T, TResult>? selectorExceptLast = null, Func<T, TResult>? selectorOnLast = null)
    {
        using var enumerator = collection.GetEnumerator();
        var isNotLast = enumerator.MoveNext();
        while (isNotLast)
        {
            var current = enumerator.Current;
            isNotLast = enumerator.MoveNext();
            var selector = isNotLast ? selectorExceptLast : selectorOnLast;
            //https://stackoverflow.com/a/32580613/294804
            if (selector != null)
            {
                yield return selector.Invoke(current);
            }
        }
    }
}

foreach (DataRow drow in ds.Tables[0].Rows)
            {
                cnt_sl1 = "<div class='col-md-6'><div class='Slider-img'>" +
                          "<div class='row'><img src='" + drow["images_path"].ToString() + "' alt='' />" +
                          "</div></div></div>";
                cnt_sl2 = "<div class='col-md-6'><div class='Slider-details'>" +
                          "<p>" + drow["situation_details"].ToString() + "</p>" +
                          "</div></div>";
                if (i == 0)
                {
                    lblSituationName.Text = drow["situation"].ToString();
                }
                if (drow["images_position"].ToString() == "0")
                {
                    content += "<div class='item'>" + cnt_sl1 + cnt_sl2 + "</div>";
                    cnt_sl1 = "";
                    cnt_sl2 = "";
                }
                else if (drow["images_position"].ToString() == "1")
                {
                    content += "<div class='item'>" + cnt_sl2 + cnt_sl1 + "</div>";
                    cnt_sl1 = "";
                    cnt_sl2 = "";
                }
                i++;
            }

另一种方法是使用Queue(队列)，我没有看到它被贴出来。这类似于实现SkipLast()方法而无需进行不必要的迭代。这种方法也可以让你在任何数量的最后一项上这样做。

public static void ForEachAndKnowIfLast<T>(
    this IEnumerable<T> source,
    Action<T, bool> a,
    int numLastItems = 1)
{
    int bufferMax = numLastItems + 1;
    var buffer = new Queue<T>(bufferMax);
    foreach (T x in source)
    {
        buffer.Enqueue(x);
        if (buffer.Count < bufferMax)
            continue; //Until the buffer is full, just add to it.
        a(buffer.Dequeue(), false);
    }
    foreach (T item in buffer)
        a(item, true);
}

要调用它，你需要执行以下操作:

Model.Results.ForEachAndKnowIfLast(
    (result, isLast) =>
    {
        //your logic goes here, using isLast to do things differently for last item(s).
    });

你可以只使用一个for循环，不需要在for体中添加额外的if:

for (int i = 0; i < Model.Results.Count - 1; i++) {
    var item = Model.Results[i];
}

for条件中的-1负责跳过最后一项。

只需存储之前的值，并在循环中使用它。然后在最后，“previous”值将是最后一项，让您以不同的方式处理它。不需要计数或特殊库。

bool empty = true;
Item previousItem;

foreach (Item result in Model.Results)
{
    // Alternatively, check if previousItem == null
    // if your Enumerable can't contain nulls
    if (!empty)
    {
        // We know this isn't the last item because
        // it came from the previous iteration
        handleRegularItem(previousItem);
    }

    previousItem = result;
    empty = false;
}

if (!empty)
{
    // We know this is the last item because the loop is finished
    handleLastItem(previousItem);
}