嵌套LINQ返回此方法无法转换为存储表达式exception
以下LINQ:
retval = ( from jm in entities.JobMasters where jm.UserId == userId && jm.IsRemote == false select new JobDto { JobMasterId = jm.JobMasterId, ExternalTaskId = jm.ExternalTaskId, JobDetails = ( from jd in entities.JobDetails where jd.JobMasterId == jm.JobMasterId select new JobDetailDto { ScreenFieldId = jd.ScreenFieldId, FieldValue = jd.FieldValue } ).ToList() } ).ToList();
给我这个错误:
LINQ to Entities无法识别方法’System.Collections.Generic.List`1 [KernWcfTest.DataTransferObjects.JobDetailDto] ToList [JobDetailDto](System.Collections.Generic.IEnumerable`1 [KernWcfTest.DataTransferObjects.JobDetailDto])’方法,并且此方法无法转换为商店表达式。
以下是两个dto类:
[DataContract] public class JobDetailDto { [DataMember] public int ScreenFieldId { get; set; } [DataMember] public string FieldValue { get; set; } } [DataContract] [KnownType(typeof(JobDetailDto))] public class JobDto { [DataMember] public int JobMasterId { get; set; } [DataMember] public string ExternalTaskId { get; set; } [DataMember] public List JobDetails { get; set; } }
问题是sub-select和JobDetails列表。 我尝试添加KnownType但它没有用。
这一切都在LINQ Pad中正常工作。
有任何想法吗?
干杯
史蒂夫
不要在内部查询(JobDetails的那个)上调用ToList。 错误是“你说的.ToList方法 – 它无法转换为T-SQL!”
这应该工作:
retval = ( from jm in entities.JobMasters where jm.UserId == userId && jm.IsRemote == false select new JobDto { JobMasterId = jm.JobMasterId, ExternalTaskId = jm.ExternalTaskId, JobDetails = from jd in entities.JobDetails where jd.JobMasterId == jm.JobMasterId select new JobDetailDto { ScreenFieldId = jd.ScreenFieldId, FieldValue = jd.FieldValue } ) } ).ToList();
请注意,您可以在查询结束时调用ToList,因为该部分不需要转换为T-SQL。