Question

我的c＃字典有问题。我想检索要使用的列表

ErrDict.Where(x => x.Key == kurumVKN).Select(x => x.Value) as List<ErrorModel>;

但它返回null。我怎样才能获得字典的列表？

Dictionary<string,List<ErrorModel> ErrDict = new Dictionary<string,List<ErrorModel>();
 if (ErrDict == null)
     {
       ErrDict = new Dictionary<string, List<ErrorModel>>(); 
     }

List<ErrorModel> listErrModel = ErrDict.Where(x => x.Key == kurumVKN).Select(x => x.Value) as List<ErrorModel>;
 if (listErrModel == null)
     {
        listErrModel=new List<ErrorModel>();
     }
        listErrModel.Add(errModel);
        ErrDict.Remove(kurumVKN);
        ErrDict.Add(kurumVKN, listErrModel);

Answer 1

您需要在ToList和Select之后致电SelectMany以展开返回List<ErrorModel>列表的查询。试试这个：

var list = ErrDict.Where(x => x.Key == kurumVKN)
           .Select(x => x.Value)
           .SelectMany(x => x) // we add this to get only a single List<ErrorModel>
           .ToList();

Answer 2

你可以尝试这个：

var result = ErrDict.Where(x => x.Key == kurumVKN).Select(x => x.Value).ToList();

为了避免Adam在他的评论中正确指出，你必须将上述内容更改为以下内容：

 var result = ErrDict.Where(x => x.Key == kurumVKN).SelectMany(x => x.Value).ToList();

Answer 3

首先，您应该尝试

ErrDict.Where(x => x.Key == kurumVKN).SelectMany(x => x.Value).ToList<ErrorModel>();

Answer 4

试试这个

List<ErrorModel> listErrModel = ErrDict.Where(x => x.Key == kurumVKN)
                                       .SelectMany(x => x.Value)
                                       .ToList<ErrorModel>();

使用linq选择Dictionary's List

4 个答案: