extension-methods

edit 2015 This question and its answers are no longer relevant. It was asked before the advent of C# 6, which has the null propagating opertor (?.), which obviates the hacky-workarounds discussed in this question and subsequent answers. As of 2015, in C# you should now use Form.ActiveForm?.ActiveControl?.Name. I've been thinking about the null propagation problem in .NET, which often leads to ugly, repeated code like this: Attempt #1 usual code: string activeControlName = null; var activeForm = Form.ActiveForm; if (activeForm != null) { var activeControl = activeForm.ActiveControl; if

In C# you can write: using System.Numerics; namespace ExtensionTest { public static class MyExtensions { public static BigInteger Square(this BigInteger n) { return n * n; } static void Main(string[] args) { BigInteger two = new BigInteger(2); System.Console.WriteLine("The square of 2 is " + two.Square()); } }} How would this simple extension method look like in Scala? Mitch Blevins The Pimp My Library pattern is the analogous construction: object MyExtensions { implicit def richInt(i: Int) = new { def square = i * i } } object App extends Application { import MyExtensions._ val two = 2

I want to add a convenience util method on to gorilla/mux Route and Router types: package util import( "net/http" "github.com/0xor1/gorillaseed/src/server/lib/mux" ) func (r *mux.Route) Subroute(tpl string, h http.Handler) *mux.Route{ return r.PathPrefix("/" + tpl).Subrouter().PathPrefix("/").Handler(h) } func (r *mux.Router) Subroute(tpl string, h http.Handler) *mux.Route{ return r.PathPrefix("/" + tpl).Subrouter().PathPrefix("/").Handler(h) } but the compiler informs me Cannot define new methods on non-local type mux.Router So how would I achieve this? Do I create a new struct type that has

I wrote the extension method GenericExtension . Now I want to call the extension method Extension . But the value of methodInfo is always null. public static class MyClass { public static void GenericExtension<T>(this Form a, string b) where T : Form { // code... } public static void Extension(this Form a, string b, Type c) { MethodInfo methodInfo = typeof(Form).GetMethod("GenericExtension", new[] { typeof(string) }); MethodInfo methodInfoGeneric = methodInfo.MakeGenericMethod(new[] { c }); methodInfoGeneric.Invoke(a, new object[] { a, b }); } private static void Main(string[] args) { new Form

Background: I had a static class, but the static methods weren't extension methods. I decided to refactor the methods into extension methods and didn't expect any code to break since extension methods can be called like static methods. However, code did break when static import was used for the static class holding the extension methods. Example: I have a static class with an extension method and a static method: namespace UsingStaticExtensionTest.Extensions { static class ExtensionClass { internal static void Test1(this Program pg) { System.Console.WriteLine("OK"); } internal static void

What namespace do I need to get my extension to work Here is my Extension Method using System; using System.Collections.Generic; using System.Web; using System.Data; namespace MyUtilities { public static class DataReaderExtensions { public static DataTable ToDataTable(IDataReader reader) { DataTable table = new DataTable(); table.Load(reader); return table; } } } When I try to use it in like this Session["Master"] = cust.GetCustomerOrderSummary((string)Session["CustomerNumber"]).ToDataTable(); it doesn't work. This is .net 2.0 You can't. C# 2.0 doesn't have extension methods at all. You can

Lets say I have 2 extension methods to string, in 2 different namespaces: namespace test1 { public static class MyExtensions { public static int TestMethod(this String str) { return 1; } } } namespace test2 { public static class MyExtensions2 { public static int TestMethod(this String str) { return 2; } } } These methods are just for example, they don't really do anything. Now lets consider this piece of code: using System; using test1; using test2; namespace blah { public static class Blah { public Blah() { string a = "test"; int i = a.TestMethod(); //Which one is chosen ? } } } The Question