You have to modify the contents of the List<string> passed to the extension method, not the variable that holds the reference to the list: public static void ForceSpaceGroupsToBeTabs(this List<string> lines) { string spaceGroup = new String(‘.’, 4); for (int i = 0; i < lines.Count; i++) { lines[i] = lines[i].Replace(spaceGroup, “T”); } }
Extension methods were not added to .NET until 3.5. However, it was not a change to the CLR, but a change to the compiler that added them, so you can still use them in your 2.0 and 3.0 projects! The only requirement is you must have a compiler that can create 3.5 projects to be … Read more
EDIT: I’ve now blogged about this in more detail. My original (and I now believe incorrect) thought: generic constraints aren’t taken into account during the overload resolution and type inference phases – they’re only used to validate the result of the overload resolution. EDIT: Okay, after a lot of going round on this, I think … Read more
We independently came up with the exact same extension method name and implementation: Null-propagating extension method. So we don’t think it’s confusing or an abuse of extension methods. I would write your “multiple levels” example with chaining as follows: propertyValue1 = myObject.IfNotNull(o => o.ObjectProp).IfNotNull(p => p.StringProperty); There’s a now-closed bug on Microsoft Connect that proposed … Read more
You should create Begin and End extension methods as well. And if you use generics, you can make the call look a little nicer. public static class ControlExtensions { public static void InvokeEx<T>(this T @this, Action<T> action) where T : Control { if (@this.InvokeRequired) { @this.Invoke(action, new object[] { @this }); } else { if … Read more
First, here’s a very quick tutorial on extensions for those learning c#/Unity for anyone googling here: Make a new text file HandyExtensions.cs like this … (note that somewhat confusingly, you can use any name at all for the class which “holds” your extensions – the actual name of the class is never used at all, … Read more
When the compiler searches for extension methods, it starts with those declared in classes in the same namespace as the calling code, then works outwards until it reaches the global namespace. So if your code is in namespace Foo.Bar.Baz, it will first search Foo.Bar.Baz, then Foo.Bar, then Foo, then the global namespace. It will stop … Read more
I just used the Reference Source to look into the code for Last and it checks to see if it is a IList<T> first and performs the appropriate O(1) call: public static TSource Last < TSource > (this IEnumerable < TSource > source) { if (source == null) throw Error.ArgumentNull(“source”); IList < TSource > list … Read more
Well, FindAll copies the matching elements to a new list, whereas Where just returns a lazily evaluated sequence – no copying is required. I’d therefore expect Where to be slightly faster than FindAll even when the resulting sequence is fully evaluated – and of course the lazy evaluation strategy of Where means that if you … Read more
No, this seems perfectly reasonable. There is a List<T>.AddRange() method that basically does just this, but requires your collection to be a concrete List<T>.