Comments on: Stop creating custom delegate types

By: John Hughes

John Hughes — Sat, 23 Oct 2010 07:00:12 +0000

The use of Action gives no implicit meaning of that the parameters are as opposed to a custom delegate. I personally think custom delegates are the way to go if you are exposing an API to the outside world.

By: Frank Quednau

Frank Quednau — Thu, 10 Apr 2008 07:53:38 +0000

Recently I encountered one issue with generic delegates: They cannot be marshalled to static external functions imported from some dll. In this case you will have to define your own non-generic delegate even though you may have a fitting one.

By: Jimmy Bogard

Jimmy Bogard — Mon, 31 Mar 2008 11:17:31 +0000

@Bart

If you have developers applying wholesale advice from what they read on blogs, I think your problem is in the personnel/training department.

This isn’t just my advice, it comes from Microsoft’s Framework Design Guidelines folks as well. It applies only to .NET 3.5 environments.

By: Bart Czernicki

Bart Czernicki — Sat, 29 Mar 2008 01:00:21 +0000

@bogardj

“many” is the keyword here.

I completely agree that Func/Action provide u enough overrides to not have to create a delegate. Even if, you have a method that takes 8 parameters u should be passing in an object instead probably and using a Func/Action

However, with having a mixed dev environment 2005/2008 (which we are transitioning from) it would cause MAJOR coding horrors if we had developers go on blogs and simply apply what a few people agree is a good practice.

By: Jimmy Bogard

Jimmy Bogard — Sat, 29 Mar 2008 00:26:54 +0000

@Bart

Many of the C# 3.0 features work just fine with .NET 2.0. C# 3.0 still compiles to the CLR 2.0. It’s just not as nice

Yes, this only applies to .NET 3.5. It’s still annoying creating these custom types, especially when you have APIs that expose properties and methods that are designed to work with Action/Func and something has to translate.

By: Jimmy Bogard

Jimmy Bogard — Sat, 29 Mar 2008 00:24:28 +0000

@Jon

Hooray! I knew someone would find a way for it to work easily. Thanks!

By: Jimmy Bogard

Jimmy Bogard — Sat, 29 Mar 2008 00:23:15 +0000

@Jon

Hooray! I knew someone would find a way for it to work easily. Thanks!

By: Justin Etheredge

Justin Etheredge — Fri, 28 Mar 2008 19:55:31 +0000

Here here, that is an excellent suggestion for those working on a completely 3.5 codebase.

By: Bart Czernicki

Bart Czernicki — Fri, 28 Mar 2008 19:34:50 +0000

Uhh…no. 2 reasons:

- backwards compatibility:
I could list you a few examples why u still would want custom delegate types, but say ur maintaining an API that has to work with 2.0 code…why exactly would u start using Func/Action??

Same goes for automatic properties, collection initializers, implicit anon types…all the “syntactic sugar” for C# 3.0

- standards:

The achitect should define what the best practices are and code standards are. If you ur standards are to write code a specific way and then u have developers auto update their code to what they see on a blog, ur going to have bigger problems

By: Jon Skeet

Jon Skeet — Fri, 28 Mar 2008 07:31:29 +0000

It’s not quite as bad as you’re making it out to be. Yes, there’s no direct conversion – but you don’t need to write any extra methods to convert from one to another. The following assignments both work:

match1 = new Predicate(match2);
match1 = new Predicate(match3);

No wrapper methods required.

That said, I do agree that it’s best not to create your own delegate types by and large.

Jon