PagedList Strikes Back
08 Jul 2008There is an updated version of the PagedList<T> code available on GitHub.
A few months ago I posted about my changes to Rob Conery's PagedList class. Since writing that article many comments have been left about how to further improve the design, which I have since incorporated into a new, further improved PagedList class. For those who aren't familiar, the PagedList class allows scenarios such as the following:
| public object ListProducts(int pageIndex) { | |
| int pageSize = 10; | |
| var products = productRepository.GetAllProducts().ToPagedList( pageIndex, pageSize ); | |
| return View( products ); | |
| } |
So in the above scenario (an example MVC action), if you had a list of 30 products with IDs 1-30 and passed in a pageIndex of 2 you would pass the products with IDs 21-30 into your view. Best of all it uses IQueryable, so if you pass a LINQ expression or IQueryable result into ToPagedList(...) it will do the filtering on the database side! Take a look at the new improved PagedList on GitHub.
Changes Since Previous Version:
- Changed "TotalPages" property to "PageCount". This was done to more clearly illustrate the purpose of this property (more in line with the standard List<T> .Count property).
- Changed "TotalCount" property to "TotalItemCount". This was done to differentiate between Pages and Items more clearly.
- Switched "PageIndex" back to being a zero-based index, rather than one-based. The PageIndex was set to be one-based because the most common use-case that I could think of, outputting a pager (i.e.: Previous - 1 - 2 - 3 - Next), was one-based and it would be nice to not have to do "obj.PageIndex + 1" everywhere. This was probably a poor decision. Some people found it confusing and others found that it didn't work with the standard .Net DataPager.
- Added "PageNumber" property. As suggested via comment on my previous post, PageNumber is just PageIndex + 1.
- Treat all data as IQueryable for the duration of class initialization. Tgmdbm, a frequent contributer on the ASP.Net MVC forums, pointed out some good reasons why everything should be treated as IQueryable before the .Skip(x).Take(y). I'm not 100% sold that treating it as IEnumerable would also work for IQueryable objects (since IQueryable supports IEnumerable), but to be safe I have defaulted everything to using IQueryable. You can still pass in a strict IEnumerable, but it will be converted to IQueryable for the duration of the PagedList class initialization process.
- Tested with xUnit.net. While the PagedList class isn't exactly rocket science, I want to strive to improve the quality of the code that I'm presenting to the community. I also enjoyed having an excuse to try out xUnit's data-driven testing using the [Theory] attribute (similar to MbUnit's [RowTest]) for the first time. Not much has been written about it, but I was able to find some examples from Ben Hall which got me up and testing quickly.
A big thanks to everyone who has thrown their two cents in to help improve this small but useful class!