After investigation, it turns out things aren’t quite as bad as I thought. Basically, when everything is implemented properly (GetHashCode, etc.) the documentation is correct, and the behavior is correct. But, if you try to do something like implement IEquatable all by itself, then your Equals method will never get called (this seems to be … Read more
There are multiple ways 1) var data = (from p in db.people orderby p.IdentityKey descending select p).Take(100); 2) var query = db.Models.Take(100); 3) or you can skip certain results var data = (from p in people select p).Skip(100);
This is more like an extension to @Alex’s answer. Step 1 : Set the connection property of your .dbml file to “none”. Step 2 : Create a new separate partial class with the same name as that of the existing partial class for the .dbml file. And set the connectionString property by using the parameterless … Read more
//var Country = Countries.FirstOrDefault(o => o.Id == 100000581); var personnelIds = context.Personnels .Where(p => p.Country.Id == 100000581) .Select(p => p.Id) .ToArray(); personnelIds.Dump(); Try this, it should be better.
I have now found out that I could use the Take() extension method on the IQueryOver instance, and only the enumerate to a list, like so: Result precedingOrMatchingResult = Session.QueryOver<Result>(). Where(r => r.TimeStamp < timeStamp). OrderBy(r => r.TimeStamp).Desc. Take(1).List(). //enumerate only on element of the sequence! FirstOrDefault(); //get the preceding or matching result, if there … Read more
The trick is to create a comparer that only works on inferred types. For instance: public class Comparer<T> : IComparer<T> { private Func<T,T,int> _func; public Comparer(Func<T,T,int> func) { _func = func; } public int Compare(T x, T y ) { return _func(x,y); } } public static class Comparer { public static Comparer<T> Create<T>(Func<T,T,int> func){ return … Read more
This is the kind of query that EF generates when it knows for sure that the query won’t return any results. Such a query minimizes database processing. How can EF be so sure? This can only be when for all it knows UserId in the database is not nullable. This, in turn, can only be … Read more
Code for joining 3 tables is: var list = dc.Orders. Join(dc.Order_Details, o => o.OrderID, od => od.OrderID, (o, od) => new { OrderID = o.OrderID, OrderDate = o.OrderDate, ShipName = o.ShipName, Quantity = od.Quantity, UnitPrice = od.UnitPrice, ProductID = od.ProductID }).Join(dc.Products, a => a.ProductID, p => p.ProductID, (a, p) => new { OrderID = a.OrderID, … Read more
You don’t need a join for that: var filteredEmployees = groupA.Except(groupB); Note that this will be a sequence of unique employees – so if there are any duplicates in groupA, they will only appear once in filteredEmployees. Of course, it also assumes you’ve got a reasonable equality comparer1. If you need to go specifically on … Read more
List<B> listB = listA.Select(a => new B() { Count = a.TotalCount, Title = a.Title }).ToList(); Does the same as eduncan’s solution with different syntax. Take your pick..