问题:

The Razor view engine in ASP.NET MVC supports @helper to define little helper methods. It seems you can do much the same by adding extension methods to HtmlHelper. In what situations is it best to use each?

回答1:

Subjective question, so here's my subjective and biased answer: When the helper code involves amounts of C# code use a custom HtmlHelper and when it's primary markup you could use @helper. But assuming that when you have markup you could use a partial like @Html.Partial("_foo", SomeModel) or an editor/display templates like @Html.EditorFor(x => x.Foo), the @helper doesn't really have any practical use. Personally I've never used @helper by the way, and I've never recommended it's usage to people I've been consulting.

回答2:

Yes, that's true, though the @helpers seem a bit easier to work with if there's a good chunk of markup that's included--Html extensions and more extensive markup don't go that well together, IMO.

On the other hand, @helpers can't be unit tested like Html extensions.