c# - LINQ to Entities 无法识别方法 'System.Collections.Generic.Dictionary`

Question

我有这个erun time错误异常

LINQ to Entities does not recognize the method
 'System.Collections.Generic.Dictionary`2[System.String,System.Collections.Generic.List`1[Project.Model.Value]]
ToDictionary[Value,String,List`1](System.Collections.Generic.IEnumerable`1[Project.Model.Value],
System.Func`2[Project.Model.Value,System.String],
System.Func`2[Project.Model.Value,System.Collections.Generic.List`1[Project.Model.Value]])'
method, and this method cannot be translated into a store expression.

我尽我所能修复它，但没有用。我认为来自列表的异常有人可以帮助我修复它

public IEnumerable<ItemManagement> getItemsForFormType(string formType)
        {
            using (var db = new AthenaContext())
            {

                List<Value> dropDownListValue = (from val in db.Values
                                                 where val.ParentId == (from va in db.Values
                                                                        where
                                                                            va.ParentId
                                                                            == (from value3 in db.Values
                                                                                where value3.Name == formType
                                                                            select value3.RecordId).FirstOrDefault()
                                                                    select va.RecordId).FirstOrDefault()
                                             select val).ToList();
            var result = (from value1 in db.Values
                          where value1.Name == formType
                          select
                              new ItemManagement
                              {

                                  FormType = value1.Name,
                                  RecordID = value1.RecordId,
                                  FormControllerNames =
                                  (from va in db.Values
                                   where va.ParentId == (from value3 in db.Values where value3.Name == formType select value3.RecordId).FirstOrDefault()
                                   select va).ToDictionary(va => va.Name, va => dropDownListValue)
                              }).ToList();
            return result;
        }

Answer 1

您正在尝试将 .NET 库函数嵌入到您的 EF 查询中。由于它不可转换为 SQL，因此不受支持。

您必须重写您的查询，而不使用 .ToDictionary()。

这个特殊情况可能并不难。如果完全需要投影 ToDictionary()，请重新访问。您可以使用以下方法安全地编写 SQL 可翻译投影:

.Select( new { anyName: <expression>, otherName: <otherExpression>, etc })