从字典中删除项目，同时迭代它 [英] delete item from dictionary while iterating over it

问题描述

我有字典（buzzCompaignsPerUserIntersets），我有字典（key = stringand value = ICollection），我想删除从每个键的值，compaign wich验证条件这里是我使用的代码：

ihave probleme with Dictionary(buzzCompaignsPerUserIntersets) , i have dictionary (key = stringand value = ICollection), i want to remove from value of each key , compaign wich verify condition here is the code who i used :

      buzzCompaignsPerUserIntersets = Dictionary<string, ICollection<Buzzcompaign> ;

        foreach(var dic_compaign in buzzCompaignsPerUserIntersets)
        {

             var listCompaign = buzzCompaignsPerUserIntersets[dic_compaign.Key];
             for (int i = 0; i < listCompaign.Count(); i++)
             {
                 if (listCompaign.ElementAt(i).MayaMembership.MayaProfile.MayaProfileId == profile_id)
                                 buzzCompaignsPerUserIntersets[dic_compaign.Key].Remove(listCompaign.ElementAt(i));         
              }                
        }

这个代码我有奇怪的结果，因为我迭代一个字典，我从中删除元素，有任何建议

with this code i have strange result because i iterate over a dictionary wich i remove element from them , have you any suggestion

推荐答案

使用 ElementAt ）不是获取特定项目的理想方式，并且性能不佳。它的用法建议你想要一个索引器的集合，如 IList< T> 。

The use of ElementAt(i) is not the ideal way to get a particular item and will perform poorly. Its usage suggests that you want a collection with an indexer, such as IList<T>.

您可以使用这种方法：

foreach(var key in buzzCompaignsPerUserIntersets.Keys)
{
     var list = buzzCompaignsPerUserIntersets[key];
     var query = list.Where(o => o.MayaMembership
                                  .MayaProfile.MayaProfileId == profile_id)
                     .ToArray();
     foreach (var item in query)
     {
         list.Remove(item);
     }
}

或者，如果您可以更改 ICollection< T> 到 IList< T> ，您可以使用索引器和 RemoveAt 方法。它看起来像这样：

Alternately, if you can change the ICollection<T> to an IList<T> you could use the indexer and the RemoveAt method. That would look like this:

foreach(var key in buzzCompaignsPerUserIntersets.Keys)
{
     var list = buzzCompaignsPerUserIntersets[key];
     for (int i = list.Count - 1; i >= 0; i--)
     {
         if (list[i].MayaMembership.MayaProfile.MayaProfileId == profile_id)
         {
             list.RemoveAt(i);
         }
     }
}

A List< T> 将允许您使用 RemoveAll 方法。如果您对这项工作感兴趣，请参阅我对另一个问题的回答。

A List<T> would let you use the RemoveAll method. If you're interested in how that works take a look at my answer to another question.

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