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c#asp.net-mvclinqentity-frameworkasp.net-mvc-5
Benafsh Yalda
Benafsh Yalda

Reputation: 396

Linq Limiting records gives error for paging?

I want to create pagination my LINQ query gives error:

var query = from c in db.Projects.Take(2).Skip(2) orderby c.ProjectId descending select c;

gives the following error:

$exception  {"The method 'Skip' is only supported for sorted input in LINQ to Entities. The method 'OrderBy' must be called before the method 'Skip'."} System.Exception {System.NotSupportedException}

Upvotes: 0

Views: 372

Answers (2)

Dawid O
Dawid O

Reputation: 6341

Try:

var query = (from c in db.Projects orderby c.ProjectId descending select c).AsEnumerable().Skip(2).Take(2)

Or More efficient (Credit to Jon Skeet)

var query = (from c in db.Projects orderby c.ProjectId descending select c).Skip(2).Take(2)

Upvotes: 4

Jon Skeet
Jon Skeet

Reputation: 1501163

The error describes exactly what is required - your sequence needs to be ordered before skip/take many any sense. You already know what ordering you want - you've just got to make it happen earlier in the logical pipeline than the paging. Additionally, there's really no benefit in using a query expression here. I suggest you use:

var query = db.Projects
              .OrderByDescending(c => c.ProjectId)
              .Skip(2)
              .Take(2);

(That can all be in one line if you really want it to be, but I find it simpler to understand the pipeline if it's laid out vertically.)

Note that I've also inverted the order of Skip and Take - you almost never want Take before Skip... in your sample code, you've shown Take(2).Skip(2) which could never return any results... the result of the Take(2) part is a sequence with at most two results, and then the Skip(2) is skipping the first two of those results... leaving nothing. Typically you have something like:

.Skip((pageNumber - 1) * pageSize)
.Take(pageSize)

Upvotes: 4

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