Question

I’m attempting to write a search function for a database table that needs to access information from related tables using Entity Framework. However, I’m running into problems getting the data back out of my initial query after doing a join on the parent table and the related tables. My code currently looks like this. I initialize my queryable object

IQueryable<PurchaseOrder> po = _context.PurchaseOrders;

Where PurchaseOrder is an Entity type. Then there is a series of blocks like this.

if (!String.IsNullOrEmpty(searchViewModel.Comment)){
     var helper = _context.PurchaseOrderComments.Where(x => x.CommentText.Contains(searchViewModel.Comment));

     var mid = po.Join(helper, r => r.PurchaseOrderID, u => u.PurchaseOrderID, (r, u) =>
                new
                {
                    PurchaseOrderID = r.PurchaseOrderID,
                    PurchaseOrderNumber = r.PurchaseOrderNumber,
                    VendorID = r.VendorID,
                    ContractNumber = r.ContractNumber,
                    BuyerUserID = r.BuyerUserID
                });

     po = mid.Select(x => new PurchaseOrder
            {
                PurchaseOrderID = x.PurchaseOrderID,
                PurchaseOrderNumber = x.PurchaseOrderNumber,
                VendorID = x.VendorID,
                ContractNumber = x.ContractNumber,
                BuyerUserID = x.BuyerUserID
            });
 }

After each block, po is passed to the next search parameter. However, as you might guess, my program complains that I can’t build a complex type in mid’s Select statement. I’ve also tried building PurchaseOrder objects from the contents of mid, inserting them into a new List of PurchaseOrders, and converting that list into a queryable to assign to po to pass on to the next block. However, that changes po’s data type from System.Data.Object.ObjectSet to System.Collections.Generic.List, which then throws an InvalidOperationException the next time I try and iterate through it using a foreach.

So my question is, are there any obvious mistakes in my approach or any suggestions for other ways to approach the problem? Thanks very much for any help.

Answer 1

I think you’re making this more complicated than it needs to be. If I understand what you’re trying to do, you should be able to do something like this:

if (!String.IsNullOrEmpty(searchViewModel.Comment)){
  po = po.Where(
     o => o.PurchaseOrderComments.Any(
       c => c.CommentText.Contains(searchViewModel.Comment)));
}