If you’re using .NET 3.5 or .NET 4, it’s easy to create the dictionary using LINQ: Dictionary<string, ArrayList> result = target.GetComponents() .ToDictionary(x => x.Key, x => x.Value); There’s no such thing as an IEnumerable<T1, T2> but a KeyValuePair<TKey, TValue> is fine.
Yes, LINQ to Objects supports this with Enumerable.Concat: var together = first.Concat(second); NB: Should first or second be null you would receive a ArgumentNullException. To avoid this & treat nulls as you would an empty set, use the null coalescing operator like so: var together = (first ?? Enumerable.Empty<string>()).Concat(second ?? Enumerable.Empty<string>()); //amending `<string>` to the … Read more
If X can really be cast to Y you should be able to use List<Y> listOfY = listOfX.Cast<Y>().ToList(); Some things to be aware of (H/T to commenters!) You must include using System.Linq; to get this extension method This casts each item in the list – not the list itself. A new List<Y> will be created … Read more
for example, when to use it over foreach? You don’t use IEnumerable “over” foreach. Implementing IEnumerable makes using foreach possible. When you write code like: foreach (Foo bar in baz) { … } it’s functionally equivalent to writing: IEnumerator bat = baz.GetEnumerator(); while (bat.MoveNext()) { bar = (Foo)bat.Current … } By “functionally equivalent,” I mean … Read more
Inside a method that returns IEnumerable<T>, yield return has to return T, not an IEnumerable<T>. Replace yield return c.GetDeepControlsByType<T>(); with: foreach (var x in c.GetDeepControlsByType<T>()) { yield return x; }
You can do this very simply using LINQ. Make sure this using is at the top of your C# file: using System.Linq; Then use the ToList extension method. Example: IEnumerable<int> enumerable = Enumerable.Range(1, 300); List<int> asList = enumerable.ToList();
IEnumerable doesn’t support this. This is by design. IEnumerable uses lazy evaluation to get the elements you ask for just before you need them. If you want to know the number of items without iterating over them you can use ICollection<T>, it has a Count property.
You can use list ?? Enumerable.Empty<Friend>(), or have FindFriends return Enumerable.Empty<Friend>() This can be found under the System.Linq namespace.
Well, if the method expects an IEnumerable you’ve got to pass something that is a list, even if it contains one element only. passing new[] { item } as the argument should be enough I think
First of all, IQueryable<T> extends the IEnumerable<T> interface, so anything you can do with a “plain” IEnumerable<T>, you can also do with an IQueryable<T>. IEnumerable<T> just has a GetEnumerator() method that returns an Enumerator<T> for which you can call its MoveNext() method to iterate through a sequence of T. What IQueryable<T> has that IEnumerable<T> doesn’t … Read more