You cannot, because IEnumerable<T> does not necessarily represent a collection to which items can be added. In fact, it does not necessarily represent a collection at all! For example: IEnumerable<string> ReadLines() { string s; do { s = Console.ReadLine(); yield return s; } while (!string.IsNullOrEmpty(s)); } IEnumerable<string> lines = ReadLines(); lines.Add(“foo”) // so what is … Read more
Just stumbled into this oldie… To do this without the dynamic LINQ library, you just need the code as below. This covers most common scenarios including nested properties. To get it working with IEnumerable<T> you could add some wrapper methods that go via AsQueryable – but the code below is the core Expression logic needed. … Read more
IEnumerable describes behavior, while List is an implementation of that behavior. When you use IEnumerable, you give the compiler a chance to defer work until later, possibly optimizing along the way. If you use ToList() you force the compiler to reify the results right away. Whenever I’m “stacking” LINQ expressions, I use IEnumerable, because by … Read more
There is no ForEach extension for IEnumerable; only for List<T>. So you could do items.ToList().ForEach(i => i.DoStuff()); Alternatively, write your own ForEach extension method: public static void ForEach<T>(this IEnumerable<T> enumeration, Action<T> action) { foreach(T item in enumeration) { action(item); } }
Yes, both will give you deferred execution. The difference is that IQueryable<T> is the interface that allows LINQ-to-SQL (LINQ.-to-anything really) to work. So if you further refine your query on an IQueryable<T>, that query will be executed in the database, if possible. For the IEnumerable<T> case, it will be LINQ-to-object, meaning that all objects matching … Read more