It really depends on how to want to expose your repository/data store. Not sure what you mean by “the context will be closed, therefore i cannot do business logic”. Do your business logic inside the using statement. Or if your business logic is in a different class, then let’s continue. 🙂 Some people return concrete … Read more
Have a look at the Except method, which you use like this: var resultingList = listOfOriginalItems.Except(listOfItemsToLeaveOut, equalityComparer) You’ll want to use the overload I’ve linked to, which lets you specify a custom IEqualityComparer. That way you can specify how items match based on your composite key. (If you’ve already overridden Equals, though, you shouldn’t need … Read more
ybo’s answer would have been my first response too. The query expression equivalent of this is: var query = from a in computeAList() from b in a.Alist select b.C; For the sake of completeness, the other answers in this thread are variations on the same theme. From ybo (the exact same query, expressed as dot … Read more
Assuming you can group all the null Programs together and Id will be non-negative, how about something like this: GroupBy(x => x.Programa == null ? -1 : x.Programa.Id)
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
Using reflection and expression-trees you can provide the parameters and then call OrderBy function, Instead of returning Expression<Func<Task, T>> and then calling OrderBy. Note that OrderBy is an extension method and has implemented in both System.Linq.Enumarable and System.Linq.Queryable classes. The first one is for linq-to-objects and the latter is for linq-to-entities. entity-framework needs the expression … Read more
Both Marc‘s and dahlbyk‘s answers seem to work very well. I have a much simpler solution though. Instead of using Distinct, you can use GroupBy. It goes like this: var listDistinct = list.GroupBy( i => i.value1, (key, group) => group.First() ).ToArray(); Notice that I’ve passed two functions to the GroupBy(). The first is a key … Read more
How about: var most = list.GroupBy(i=>i).OrderByDescending(grp=>grp.Count()) .Select(grp=>grp.Key).First(); or in query syntax: var most = (from i in list group i by i into grp orderby grp.Count() descending select grp.Key).First(); Of course, if you will use this repeatedly, you could add an extension method: public static T MostCommon<T>(this IEnumerable<T> list) { return … // previous code … Read more
int[] intarray = { 1, 2, 3, 4, 5 }; string[] result = intarray.Select(x=>x.ToString()).ToArray();
If you’re worried about performance, the following code will stop as soon as it finds the first duplicate item – all the other solutions so far require the whole input to be iterated at least once. var hashset = new HashSet<string>(); if (myList.Where(s => s != null).Any(s => !hashset.Add(s))) { // there are duplicates } … Read more