如何在不使用LINQ to SQL和Entity Framework对数据库进行过多调用的情况下优化此查询？

Question

I have this anonymous type that I'm building through repository calls form Entity Framework but am getting this error: The specified LINQ expression contains references to queries that are associated with different contexts. The code below only pulls from one database so I do not understand why this is being raised.

// listOfReportIDs is a list of ints
var reports = BusinessLogic.Repository.Read<Report>().Where(r => listOfReportIDs.Contains(r.ReportID));
var huForm = BusinessLogic.Repository.Read<HumanCase>().Where(h => listOfReportIDs.Contains(h.ReportID));
var anForm = BusinessLogic.Repository.Read<AnimalCase>().Where(a => listOfReportIDs.Contains(a.ReportID));

var reportSummaryData = from r in reports
                        from h in huForm.Where(h => h.ReportID == r.ReportID)
                        from a in anForm.Where(a => a.ReportID == r.ReportID)
                        select new
                        {
                            CDC_ReportID = r.CDCReportID,
                            StateReportID = r.StateReportID,
                            r.ReportDate,
                            ReportStatus = r.LookupReportStatus.LookupReportStatusName,
                            r.AuthorID,
                            h.HumanComment,
                            a.AnimalComment
                        };

var reportData = reportSummaryData.ToList();

When I call the ToList() method above at the end (in order to cut down calls to the db til the end), I get the error mentiond above about multiple contexts. They all come from the same single database, just different tables, why is this still being thrown and how can I fix it in order to only make one call to the db?

EDIT:

Read method:

public IQueryable<T> Read<T>() where T : EntityObject, new()
{
    var objectSet = Context.CreateObjectSet<T>();
    objectSet.MergeOption = MergeOption.PreserveChanges;
    return objectSet;
}

Answer 1

The multiple contexts refers to reports, huForm and anForm. You need to move these to the same context, or use separate queries to get the data from the database, and join then join the results.

Each of those reads is giving you a separate context. You need to abstract your db connection and then inherit to each of the models.