如何解决“方法'Skip'仅支持LINQ to Entities中的排序输入." [英] How to solve "The method 'Skip' is only supported for sorted input in LINQ to Entities."

问题描述

当我使用"LINQ到实体"来显示每个产品并在ASP.NET MVC中实现分页时，出现了此错误.

I got this error when I was using "LINQ to entities" to show every single product and implement paging in ASP.NET MVC.:

The method 'Skip' is only supported for sorted input in LINQ to Entities.
The method 'OrderBy' must be called before the method 'Skip'."

LINQ:

Model.Name = db.Products.Where(p => p.ProductSubcategoryID == id)
                        .Skip((page - 1) * pageSize)
                        .Take(pageSize)
                        .ToList();

我该如何解决?如果我放OrderBy而不是Where会怎样?

How can I fix it? What would happen if I put OrderBy instead of Where?

推荐答案

您不要用OrderBy代替Where" ...而是将它们组合在一起:

You don't "put OrderBy instead of Where"...you combine them:

Model.Name = db.Products.Where(p => p.ProductSubcategoryID == id)
                        .OrderBy(p => p.ProductSubcategoryID) // <---- this
                        .Skip((page - 1) * pageSize)
                        .Take(pageSize)
                        .ToList();

这是必需的，因为生成的SQL会产生类似以下内容的信息:

This is required because the generated SQL will produce something like:

WHERE generated_id BETWEEN x AND y

如果您没有明确告诉数据库服务器返回结果的顺序，则您的结果每次(可能)都将有所不同.而如果您按字段排序，则可以保证它们按顺序排列出来，因此您的分页将产生一致的结果.

If you don't explicitly tell the DB server what order to return results in...your results would be different (possibly) every time. Whereas, if you order by a field, they are guaranteed to come out in order and therefore your paging will produce consistent results.

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