不允许在查询中显式构造实体类型“”

Question

我收到以下错误

Explicit construction of entity type '...TableClassName' in query is not allowed.

Server stack trace: 
   at System.ServiceModel.Channels.ServiceChannel.ThrowIfFaultUnderstood(Message reply, MessageFault fault, String action, MessageVersion version, FaultConverter faultConverter)
   at System.ServiceModel.Channels.ServiceChannel.HandleReply(ProxyOperationRuntime operation, ProxyRpc& rpc)
   at System.ServiceModel.Channels.ServiceChannel.Call(String action, Boolean oneway, ProxyOperationRuntime operation, Object[] ins, Object[] outs, TimeSpan timeout)
   at System.ServiceModel.Channels.ServiceChannelProxy.InvokeService(IMethodCallMessage methodCall, ProxyOperationRuntime operation)
   at System.ServiceModel.Channels.ServiceChannelProxy.Invoke(IMessage message)

这是我的代码。

tgdd = new List<TableClassName>();
    context.DeferredLoadingEnabled = false;
    var t = context.TableClassName.Where(...)
                                  .GroupBy(g => new { g.Date, g.UserID })
                                  .Select(g => new TableClassName
                                  {
                                        PK = 1,
                                        Date = Convert.ToDateTime(g.Key),
                                        Counted = g.Sum(x => x.Counted),
                                        Time = g.Sum(x => x.Time),
                                        MaxHR = g.Max(x => x.MaxHR),
                                        PeakCal = g.Max(x => x.PeakCal),
                                        PowerIndex = (g.Sum(x => x.PowerIndex)),
                                        Target = g.Max(x => x.Target),
                                        RepTotal = g.Sum(x => x.RepTotal),
                                        Lifted = g.Sum(x => x.Lifted),
                                        UserID = Convert.ToInt64(g.Key)
                                   }).ToList();

                        foreach (TableClassName r in t)
                        {
                            tgdd.Add(r);
                        }

我没有语法错误。这是一个网络服务。我在调用它时遇到了问题。

Answer 1

考虑以下几点：

context.DeferredLoadingEnabled = false; 
tgdd = context.TableClassName.Where(...) 
                             .GroupBy(g => new { g.Date, g.UserID })
                             .AsEnumerable() 
                             .Select(g => new TableClassName 
                             { 
                                   PK = 1, 
                                   Date = Convert.ToDateTime(g.Key), 
                                   Counted = g.Sum(x => x.Counted), 
                                   Time = g.Sum(x => x.Time), 
                                   MaxHR = g.Max(x => x.MaxHR), 
                                   PeakCal = g.Max(x => x.PeakCal), 
                                   PowerIndex = (g.Sum(x => x.PowerIndex)), 
                                   Target = g.Max(x => x.Target), 
                                   RepTotal = g.Sum(x => x.RepTotal), 
                                   Lifted = g.Sum(x => x.Lifted), 
                                   UserID = Convert.ToInt64(g.Key) 
                              }).ToList(); 

通过在 Group 操作之后调用 AsEnumerable，我们将投影强制投射到客户端的自定义类型中，而不是在服务端不知道您的自定义类型的服务器中。此外，通过在查询上调用 ToList，您无需遍历结果并将它们添加到另一个列表中。只需将第一个 ToList 的结果直接分配给您要返回的对象即可。

Answer 2

我使用匿名类型来解决这个问题（删除了关键字“new”之后的 TableClassName）。

然后我遇到了另一个问题，使用我的 TableClassName 遍历 var（由于 var 中的内容是匿名的而导致错误）。

我遍历 var，使用 var，然后将每个 var 的内容一一提取到我的对象中，然后按原意将对象添加到我的列表中。这是我的代码。

foreach (var v in t)
{
    TableClassName tgData = new TableClassName();
    tgData.PK = v.PK;
    tgData.Date = v.Date;
    tgData.Counted= v.Counted;
    tgData.Time = v.Time;
    tgData.MaxHR = v.MaxHR;
    tgData.PeakCal = v.PeakCal;
    tgData.PowerIndex = v.PowerIndex;
    tgData.Target = v.Target;
    tgData.RepTotal = v.RepTotal;
    tgData.Lifted = v.Lifted;
    tgData.UserID = v.UserID;
    tgdd.Add(tgData);
}

希望这对某人有所帮助。

Answer 3

尝试从 LINQ 查询中分离出“新 TableClassName”部分。

你可能想看看这个帖子：

http://social.msdn.microsoft.com/forums/en-US/linqprojectgeneral/thread/1ce25da3-44c6-407d-8395-4c146930004b/

“实体的使用模式是它们在查询之外创建并通过 DataContext 插入表中，然后通过查询检索，而不是由查询创建”

Answer 4

这是可能的，如果你创建一个没有 [Table]-Attribute 的新派生类，如下所示：

public class TableClassNameLocal : TableClassName
{
}

然后您可以在选择中创建“TableClassNameLocal”的实例。将新实例直接转换为“TableClassName”，它将起作用！

result = new List<TableClassName>();
context.DeferredLoadingEnabled = false;
var t = context.TableClassName.Where(...)
                              .GroupBy(g => new { g.Date, g.UserID })
                              .Select(g => (TableClassName)new TableClassNameLocal
                              {
                                    PK = 1,
                                    Date = Convert.ToDateTime(g.Key),
                                    Counted = g.Sum(x => x.Counted),
                                    Time = g.Sum(x => x.Time),
                                    MaxHR = g.Max(x => x.MaxHR),
                                    PeakCal = g.Max(x => x.PeakCal),
                                    PowerIndex = (g.Sum(x => x.PowerIndex)),
                                    Target = g.Max(x => x.Target),
                                    RepTotal = g.Sum(x => x.RepTotal),
                                    Lifted = g.Sum(x => x.Lifted),
                                    UserID = Convert.ToInt64(g.Key)
                               }).ToList();

Answer 5

这对我有用：

  var roles = (from r in roleNames
                                    join rm in DataContext.FMC_RoleMaps on r equals rm.RoleName_old
                                    select new
                                    {
                                        dnnUser.UserID,
                                        rm.RoleID
                                    }
                                           );
                       foreach (var userRole in roles)
                       {
                           var newrole = new UserRole()
                                             {
                                                 RoleID = userRole.RoleID,
                                                 UserID = userRole.UserID
                                             };
                           DataContext.UserRoles.InsertOnSubmit(newrole);
                       }