我有一个foreach循环,需要执行一些逻辑时,最后一项是从列表中选择,例如:

 foreach (Item result in Model.Results)
 {
      //if current result is the last item in Model.Results
      //then do something in the code
 }

我可以知道哪个循环是最后没有使用循环和计数器吗?


当前回答

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++;
            }

其他回答

".Last()"对我不起作用,所以我不得不这样做:

Dictionary<string, string> iterativeDictionary = someOtherDictionary;
var index = 0;
iterativeDictionary.ForEach(kvp => 
    index++ == iterativeDictionary.Count ? 
        /*it's the last item */ :
        /*it's not the last item */
);

使用Linq和foreach:

foreach (Item result in Model.Results)   
{   
     if (Model.Results.IndexOf(result) == Model.Results.Count - 1) {
             // this is the last item
     }
}

https://code.i-harness.com/en/q/7213ce

接受的答案将不适用于集合中的副本。如果设置在foreach上,则可以添加自己的索引变量。

int last = Model.Results.Count - 1;
int index = 0;
foreach (Item result in Model.Results)
{
    //Do Things

    if (index == last)
        //Do Things with the last result

    index++;
}

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
    }
}