IQueryable objects are produced by Queryable Providers (ex. LINQ to SQL, LINQ to Entities/Entity Framework, etc). Virtually nothing you can instantiate with new in the basic .NET Framework implements IQueryable. IQueryable is an interface designed to be used to create Queryable providers, which allow the LINQ library to be leveraged against an external data store … Read more
AsQueryable just creates a query, the instructions needed to get a list. You can make futher changes to the query later such as adding new Where clauses that get sent all the way down to the database level. AsList returns an actual list with all the items in memory. If you add a new Where … Read more
Then just Select: var list = source.Select(s=>new { ID = s.ID, Name = s.Name }).ToList(); (edit) Actually – the names could be inferred in this case, so you could use: var list = source.Select(s=>new { s.ID, s.Name }).ToList(); which saves a few electrons…
IQueryable<T> is intended to allow a query provider (for example, an ORM like LINQ to SQL or the Entity Framework) to use the expressions contained in a query to translate the request into another format. In other words, LINQ-to-SQL looks at the properties of the entities that you’re using along with the comparisons you’re making … Read more
The pros; composability: callers can add filters callers can add paging callers can add sorting etc The cons; non-testability: Your repository is no longer properly unit testable; you can’t rely on a: it working, b: what it does; the caller could add a non-translatable function (i.e. no TSQL mapping; breaks at runtime) the caller could … Read more
List<int> list = new List<int>() { 1, 2, 3, 4, }; IQueryable<int> query = list.AsQueryable(); If you don’t see the AsQueryable() method, add a using statement for System.Linq.
Try this. You can create a generic type with T or a specific type by replacing T with your type name. IQueryable listOppLineData = Enumerable.Empty<T>().AsQueryable();
Yes, you just repeat the from … in clause: var words = from str in text from word in str.Split(‘ ‘) select word;
There are a few main uses. As mentioned in other answers, you can use it to mock a queryable data source using an in-memory data source so that you can more easily test methods that will eventually be used on a non-enumerable based IQueryable. You can write helper methods for manipulating collections that can apply … Read more
Maybe: Enumerable.Empty<T>().AsQueryable();