将查询结果用于另一个查询

Question

First I have BookEntity.cs

public class BookEntity
{
    public string StoreId { get; set; }
    public string IsbnNumber { get; set; }
    public DateTimeOffset RentStartTime { get; set; }
    public DateTimeOffset RentEndTime { get; set; }
}

Then use LINQ to query

var bookTable = new Table<BookEntity>(session);
var bookQuery = bookTable
                .Where(books => books.StoreId == StoreId
                             && books.IsbnNumber == IsbnNumber);

Next I have StoreEntity :

public class StoreEntity
{
    public string StoreId { get; set; }
    public LocalDate Date { get; set; }
    public DateTimeOffset Timestamp { get; set; }
    public Dictionary<string, double> Readings { get; set; } = new Dictionary<string, double>();
}

What I want is to use the result from the bookQuery as the parameter to query StoreEntity table using LINQ? (use StartTime and EndTime to compare Timestamp)

I have seen Join from the LINQ document but it does not seem what I want because I just want to return data from Store data only not both. Thanks a lot for your help.

Answer 1

I assume you want something like this:

var tmpList = new List<StoreEntity>;
foreach (BookEntity element in bookQuery)
{
  tmpList.Add(storeEntityTable.Where(x => x.StoreId == element.StoreId));
}

Correct me if I'm wrong. If that's your case I don't know why you don't want to use a join. You can retrieve the data you need anyways and it's way better in terms of performance.

//

Join query using linq:

    var query =
   from myStoreEntity in storeEntityTable
   join books in bookTable on myStoreEntity.StoreId equals books.StoreId
   where myStoreEntity.StoreId == StoreId;