The error message is pretty clear: the method where you’re calling the extension method should be marked as async. public Task<string> MyExtension(this string s) { … } public async Task MyCallingMethod() { string result = await “hi”.MyExtension(); } Re-reading this part should make much more sense now: “The ‘await’ operator can only be used within … Read more
You can’t call the extension method as a normal extension method. The instance method overrides the extension method with the same signature EDIT: You can call it as a static method ExtensionTest.MethodA(a);
Normally left joins in LINQ are modelled with group joins, sometimes in conjunction with DefaultIfEmpty and SelectMany: var leftJoin = p.Person.Where(n => n.FirstName.Contains(“a”)) .GroupJoin(p.PersonInfo, n => n.PersonId, m => m.PersonId, (n, ms) => new { n, ms = ms.DefaultIfEmpty() }) .SelectMany(z => z.ms.Select(m => new { n = z.n, m })); That will give a … Read more
It seems like not supporting Extension methods on Object was a design decision in VB. As a result, the only way we could prevent extension methods from completely breaking existing late bound code was to prevent them from being used on anything typed as object. Link
Use an extension method. Ex: namespace ExtensionMethods { public static class MyExtensionMethods { public static DateTime Tomorrow(this DateTime date) { return date.AddDays(1); } } } Usage: DateTime.Now.Tomorrow(); or AnyObjectOfTypeDateTime.Tomorrow();
Let doesn’t have its own operation; it piggy-backs off of Select. You can see this if you use “reflector” to pull apart an existing dll. it will be something like: var result = names .Select(animalName => new { nameLength = animalName.Length, animalName}) .Where(x=>x.nameLength > 3) .OrderBy(x=>x.nameLength) .Select(x=>x.animalName);
If by “warm up” you refer to JIT’ing then yes – if a method is never called it won’t have been compiled yet, so the very first time you run it it might be slower. Also refer to Does the .NET CLR JIT compile every method, every time?
It’s by explicit design. The problem is that while String most definitely implements IEnumerable<T>, most people don’t think of it, or more importantly use it, in that way. String has a fairly small number of methods. Initially we did not filter extension methods off of String and the result was a lot of negative feedback. … Read more
Since using Rails should handle this automatically I’m going to assume you’re trying to add Active Support to a non-Rails script. Read “How to Load Core Extensions“. Active Support’s methods got broken into smaller groups in Rails 3, so we don’t end up loading a lot of unneeded stuff with a simple require ‘activesupport’. Now … Read more
Like so: // you need this once (only), and it must be in this namespace namespace System.Runtime.CompilerServices { [AttributeUsage(AttributeTargets.Assembly | AttributeTargets.Class | AttributeTargets.Method)] public sealed class ExtensionAttribute : Attribute {} } // you can have as many of these as you like, in any namespaces public static class MyExtensionMethods { public static int MeasureDisplayStringWidth ( … Read more