This is a great question. First of all, here are a couple of workarounds that come to mind (they all require changes to the query): First workaround This one maybe a bit obvious and unfortunately not generally applicable: If the selection of items you would need to pass over to Enumerable.Contains already exists in a … Read more
Well, I do not agree that the injection is not possible in Dynamic Linq. What described in the answer by Ɖiamond ǤeezeƦ is correct but appies to standard Linq as constructed within the given language – C# or VB.Net or by calling extension methods like .Where with lambda functions. Then, true, it is not possible … Read more
You need to convert the code to an expression tree. using System; using System.Linq; using System.Linq.Expressions; using System.Reflection; namespace WindowsFormsApplication1 { static class Program { [STAThread] static void Main() { using (var context = new NorthwindEntities()) { IQueryable<Customer> query = context.Customers; query = Simplified<Customer>(query, “CustomerID”, “ALFKI”); var list = query.ToList(); } } static IQueryable<T> Simplified<T>(IQueryable<T> … Read more
If you need to have Ordering or Filtering on inner navigation properties (e.g. Models) then you cannot eager load them using Include method anymore. Instead, you can use EntityCollection<TEntity>.CreateSourceQuery Method like this: List years = db.Years.OrderBy(“it.Name”).ToList(); foreach(year in years) { var makesQuery = year.Makes.CreateSourceQuery().OrderBy(m => m.Name); year.Makes.Attach(makesQuery); foreach(make in year.Makes) { var modelsQuery = make.Models.CreateSourceQuery().OrderBy(m … Read more
EF seems to use INNER JOIN for including a required and LEFT OUTER JOIN for including an optional navigation property. Example: public class Order { public int Id { get; set; } public string Details { get; set; } public Customer Customer { get; set; } } public class Customer { public int Id { … Read more
As Ladislav mentioned, Include only works if you select the Ticket entity directly. Since you’re projecting other information out, the Include gets ignored. This should provide a good work-around: var data = ctx.Set<Ticket>() .Select(p => new { Ticket = p, Clients = p.Client, LastReplyDate = p.Replies.Max(q => q.DateCreated) }); First of all, each Ticket’s Clients … Read more
Never use .ToLower() to perform a case-insensitive comparison. Here’s why: It’s possibly wrong (your client collation could be, say, Turkish, and your DB collation not). It’s highly inefficient; the SQL Emitted is LOWER instead of = with a case-insensitive collation. Instead, use StringComparison.OrdinalIgnoreCase or StringComparison.CurrentCultureIgnoreCase: var q = from f in Context.Foos where f.Bar.Equals(“hi”, StringComparison.OrdinalIgnoreCase) … Read more
Use the EntityFunctions.TruncateTime method: var myQuery = from p in dbContext.Trends group p by EntityFunctions.TruncateTime(p.UpdateDateTime) into g select new { k = g.Key, ud = g.Max(p => p.Amount) };
The reason it is complaining is because it doesn’t know how to translate your Select() into a SQL expression. If you need to do a data transformation to a POCO that is not an entity, you should first get the relevant data from EF and then transform it to the POCO. In your case it … Read more
You want to use the .Include(string) method references in this “Shaping query results” article. var item = from InventoryItem item in db.Inventory.Include(“ItemTypeReference”).Include(“OrderLineItems”) where item.ID == id select item; There is probably a “sql” style syntax for the Includes as well. Also see this article about moving from LINQ-to-SQL to LINQ-to-Entities. For others looking for a … Read more