Consider this situation: public class Base { public void BaseMethod() { } } public class Sub : Base { public void SubMethod() { } } public static class Extensions { public static void ExtensionMethod(this Base @base) { } } Here are some interesting assertions about this code: I cannot call the extension method using ExtensionMethod() … Read more
EDIT: The list below applies to C# anonymous types. VB.NET has different rules – in particular, it can generate mutable anonymous types (and does by default). Jared has pointed out in the comment that the naming style is different, too. Basically this is all pretty fragile… You can’t identify it in a generic constraint, but: … Read more
No; an extension method never takes priority over an instance method with a suitable signature, and never participates in polymorphism (GetHashCode is a virtual method).
JavaScript doesn’t have an exact analogue for C#’s extension methods. JavaScript and C# are quite different languages. The nearest similar thing is to modify the prototype object of all string objects: String.prototype. In general, best practice is not to modify the prototypes of built-in objects in library code meant to be combined with other code … Read more
Another thing to keep in mind is that the string itself might be null. public static Nullable<T> ToNullable<T>(this string s) where T: struct { Nullable<T> result = new Nullable<T>(); try { if (!string.IsNullOrEmpty(s) && s.Trim().Length > 0) { TypeConverter conv = TypeDescriptor.GetConverter(typeof(T)); result = (T)conv.ConvertFrom(s); } } catch { } return result; }
In .NET 4 you can do this: String.Concat(Enumerable.Repeat(“Hello”, 4))
From the “New Features in C# 4” word doc: Dynamic lookup will not be able to find extension methods. Whether extension methods apply or not depends on the static context of the call (i.e. which using clauses occur), and this context information is not currently kept as part of the payload.
The only advantage of extension methods is code readability. That’s it. Extension methods allow you to do this: foo.bar(); instead of this: Util.bar(foo); Now there are a lot of things in C# that are like this. In other words there are many features in C# that seem trivial and don’t have great benefit in and … Read more
That will work fine (no exception). Extension methods don’t use virtual calls (i.e. it uses the “call” il instruction, not “callvirt”) so there is no null check unless you write it yourself in the extension method. This is actually useful in a few cases: public static bool IsNullOrEmpty(this string value) { return string.IsNullOrEmpty(value); } public … Read more
This post clearly describes when Include does and doesn’t have effect. The critical part is the shape of the query, i.e. the selected columns. If anything changes the shape after an Include, the Include not longer works. In your query the shape changes four times, in these statement parts: from q in _context.Cars: the query … Read more