extension-methods

问题 When i use a standard Extension Method on a List such as Where (...) the result is always IEnumerable , and when you decide to do a list operation such as Foreach() we need to Cast (not pretty) or use a ToList() extension method that (maybe) uses a new List that consumes more memory (is that right?): List<string> myList=new List<string>(){//some data}; ( Edit : this cast on't Work) myList.Where(p=>p.Length>5).Tolist().Foreach(...); or (myList.Where(p=>p.Length>5) as List<string>).Foreach(...)

问题 Good afternoon I have a class and it has an associated extension method. public class Person{ public int ID {get;set} public string Name {get;set} } Extension method: public static class Helper { public static int GetToken(this Person person){ int id = 0; //Something here is done to read token from another service... return id; } } Now I am trying to use Rhino and test this method public void readPersonToken(int personId) { var person = Person.GetPersonInfo(personId);//we consume a service

问题 Given extension method below: public static class Ext { public static void Serialize(this Guid guid_, StringWriter sw_) { sw_.Write(guid_.ToString("B")); } } and the class: public class Field<T> { public T value; public void Serialize(StringWriter sw_) { value.Serialize(sw_); } } I would like to do the following, but can't quite figure it out: public class Foo { public Field<Guid> uid; public Foo() { // assume StringWriter object sw; uid.Serialize(sw); } } Obviously real-life situation is

问题 I am trying to get a MethodInfo object for the method: Any<TSource>(IEnumerable<TSource>, Func<TSource, Boolean>) The problem I'm having is working out how you specify the type parameter for the Func<TSource, Boolean> bit... MethodInfo method = typeof(Enumerable).GetMethod("Any", new[] { typeof(Func<what goes here?, Boolean>) }); Help appreciated. 回答1: There's no way of getting it in a single call, as you would need to make a generic type constructed of the generic parameter of the method

问题 I read that you can create extension methods in Typescript and I looked up some code And put that code in my extension methods.ts but I get an error saying that toNumber doesn't exist. How can I fix this? 回答1: You can extend String interface by augmenting global scope: export { }; declare global { interface String { toNumber(): number; } } String.prototype.toNumber = function (this: string) { return parseFloat(this) }; Playground 回答2: You could extend the String interface, like this:

问题 When I try to use any extension method to my class in ascx-control: <%@ Import Namespace="VfmElita.Page.Stat" %> <%=new MyTestClass().ExtMethod() %> and here is the simplest method in the world: namespace VfmElita.Page.Stat { public static class TestExtention { public static string ExtMethod(this MyTestClass test) { return "Hope for result"; } } } (it is located in ascx.cs-file of the control I got the following error: error CS0012: The type 'System.Xml.IXmlLineInfo' is defined in an assembly

问题 I am wondering if there would be any performance difference between the following in swift : let x = 42.42 print(floor(x)) and let x = 42.42 extension Double { func myFloor() -> Double { return floor(self) } } print(x.myFloor()) 回答1: The compiler inlines the code in the second case and produces the same machine code. You can see for yourself, here. 来源： https://stackoverflow.com/questions/45558276/performance-of-swift-extensions-on-primitive-types

问题 I have a LINQ query which is attempting to get all of the distinct months of all of the dates in a table. I had this working using the Distinct() extension method. I then made it more readable by using an extension method to extract the month. And then it stopped returning Distinct results. Can anyone help me work out what happened here? As an aside, if someone can tell me the best way to get the distinct months, that would be nice too. But it's more important that I understand why this is

问题 Just out of curiosity: Many LINQ extension methods exist as both generic and non-generic variants, for example Any and Any<> , Where and Where<> etc. Writing my queries I usually use the non-generic variants and it works fine. What would be the cases when one has to use generic methods? --- edit --- P.S.: I am aware of the fact that internally only generic methods are called and the compiler tries to resolve the content of the generic brackets <> during compilation. My question is rather what

问题 https://www.raywenderlich.com/148448/introducing-protocol-oriented-programming protocol Bird { var name: String { get } var canFly: Bool { get } func doSomething() } protocol Flyable { var airspeedVelocity: Double { get } } extension Bird { // Flyable birds can fly! var canFly: Bool { return self is Flyable } func doSomething() { print("default Bird: \(name)") } } class FlappyBird: Bird, Flyable { let name: String let canFly = true var airspeedVelocity: Double = 5.0 init(name: String) { self