iqueryable

I have read some articles that state that IEnumerable used to mimic stored procedures or restrict your database. Lost lazy loading ability on the external provider. Where as IQueryable to give developers more flexibility. Lazy loading is there. In terms of performance, both consume a significant amount of performance .. so which one is more preferable? Robert Harvey From the perspective of a Repository Pattern, you can think of it this way: Use an eager loading IEnumerable when you want to pass an entire list to the client in one go. They can still add linq clauses, but the client does not

I need to be able to get something similar to the following to work: Type type = ??? // something decided at runtime with .GetType or typeof; object[] entityList = context.Resources.OfType<type>().ToList(); Is this possible? I am able to use .NET 4 if anything new in that allows this. You can call it by reflection: MethodInfo method = typeof(Queryable).GetMethod("OfType"); MethodInfo generic = method.MakeGenericMethod(new Type[]{ type }); // Use .NET 4 covariance var result = (IEnumerable<object>) generic.Invoke (null, new object[] { context.Resources }); object[] array = result.ToArray(); An

When writing a query using C# LINQ syntax, is there a way to use the Queryable.SelectMany method from the keyword syntax? For string[] text = { "Albert was here", "Burke slept late", "Connor is happy" }; Using fluent methods I could query var tokens = text.SelectMany(s => s.Split(' ')); Is there a query syntax akin to var tokens = from x in text selectmany s.Split(' ') Yes, you just repeat the from ... in clause: var words = from str in text from word in str.Split(' ') select word; You can use a Compound from Clause : var tokens = from s in text from x in s.Split(' ') select x; Your query

So I'm attempting to build a semi complication Search expression, but I'm stuck trying to create a basic one. The expressions being used for getValueExpression look something like: x => x.PropertyA != null ? x.PropertyA.ToShortDateString() : "" //nullable datetime x => x.PropertyB //string property x => x.PropertyC != null x.PropertyC.ToString() : "" //nullable int Here is my function code, it currently errors when getValueExpression being of type Func that can't be compared to a string, which makes perfect sense and I understand why that is, but I'm having trouble figuring out how to make an

I have the following expression: public Expression<Func<T, bool>> UserAccessCheckExpression<T>(int userId) where T : class { return x => (IsAdmin || userId == CurrentUserId || userId == 0); } Then I want to apply this filter to several collections (IQueryable) like this one: return tasks .Where(t => t.TaskUsers .Any(x => UserAccessCheckExpression<TaskUser>(x.User) && x.SomeBool == true)); I'm getting the following error while doing so: Error 40 Cannot implicitly convert type System.Linq.Expressions.Expression<System.Func<TaskUser,bool>> to bool I can't use workaround with interface inheritance

I do a sql query which returns a string - service name. this is the query: IQueryable<string> query = from Comp in ServiceGroupdb.ServiceGroupes where (Comp.GroupID == groupID) select Comp.Name; How do i get the string out of the query? LINQ always returns a sequence, so you have to retrieve the item out of it. If you know that you will have only one result, use Single() to retrieve that item. var item = (from Comp in ServiceGroupdb.ServiceGroupes where (Comp.GroupID == groupID) select Comp.Name).Single(); There are four LINQ methods to retrieve a single item out of a sequence: Single()

Please see this line of code. This is an invocation of a stored procedure, which returns an ObjectResult<long?> . In order to extract the long values I added the Select: dbContext.FindCoursesWithKeywords(keywords).Select(l => l.Value); Based on intellisense this Select returns IEnumerable<long> . I'm not sure whether I read it somewhere or maybe just got used to this assumption - I always thought that when the EF API returns an IEnumerable (and not IQueryable ) then this means that the results have been materialized. Meaning they've been pulled from the database. I found out today that I was