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
Why cant I use an IEnumerable with params? The question presupposes that the design team must provide a reason to not add a feature to the language. This presupposition is false. Rather, in order for a feature to be used by you it needs to be thought of, designed, specified, implemented, tested, documented and shipped. … Read more
nothing baked into the framework, but it’s a pretty straight forward extension method. See here /// <summary> /// Determines whether the collection is null or contains no elements. /// </summary> /// <typeparam name=”T”>The IEnumerable type.</typeparam> /// <param name=”enumerable”>The enumerable, which may be null or empty.</param> /// <returns> /// <c>true</c> if the IEnumerable is null or … Read more
By calling Count on IEnumerable<T> I’m assuming you’re referring to the extension method Count on System.Linq.Enumerable. Length is not a method on IEnumerable<T> but rather a property on array types in .Net such as int[]. The difference is performance. TheLength property is guaranteed to be a O(1) operation. The complexity of the Count extension method … Read more
You can call OfType<DataRow>() on the DataRowCollection.
I’m not much sure what useful it really is, as I think for most cases in the Base Library expecting an IComparer there’s an overload that expects a Comparison… but just for the record: in .Net 4.5 they’ve added a method to obtain an IComparer from a Comparison: Comparer.Create so you can pass your lambda … Read more
No, you don’t need to worry about this. The fact that they return an IDisposable implementation is an implementation detail – it’s because iterator blocks in the Microsoft implementation of the C# compiler happen to create a single type which implements both IEnumerable<T> and IEnumerator<T>. The latter extends IDisposable, which is why you’re seeing it. … Read more
Any() is asking: “Does this box contain any items?” If the box is empty, the answer is clearly no. But if there is no box in the first place, then the question makes no sense, and the function complains: “What the hell are you talking about? There is no box.” When I want to treat … Read more
Not removing but creating a new List without that element with LINQ: // remove users = users.Where(u => u.userId != 123).ToList(); // new list var modified = users.Where(u => u.userId == 123).ToList();
One important difference between IEnumerable and List (besides one being an interface and the other being a concrete class) is that IEnumerable is read-only and List is not. So if you need the ability to make permanent changes of any kind to your collection (add & remove), you’ll need List. If you just need to … Read more