使用Linq获取记录的行号 [英] Get record's row number using Linq

问题描述

我想使用Entity Framework 6从表中获取大量记录中的记录行号.

I'd like to get a record's row number inside a huge list of records from a table, using Entity Framework 6.

我尝试了以下代码:

//var currentUser = my record
var orderedUsers = dbContext.User.OrderByDescending(u => u.Age).ToList();

var userIndex = orderedUsers.IndexOf(currentUser);

ToList()方法由于超时而崩溃，因为我认为该方法会将整个列表加载到内存中.

The ToList() method crashes with a timeout, because I assume that this methods loads the whole list in memory.

如何在Linq中使用更简单的方法来获得该行号(因此，没有ToList或将所有内容都安装在内存中)?

How can I get this row number using a simpler method with Linq (so, without ToList or mounting everything in memory) ?

有关信息，我的目标是获取从起始索引到另一个索引的一系列记录.这是我为此编写的代码:

For information, my goal is to get a range of record from a start index to another index. Here's the code I wrote to do this:

var result = orderedUsers.Skip(userIndex).Take(30).ToList();

谢谢

推荐答案

使用Select的形式，该形式使用使用索引参数的lambda以及实体:

Use the form of Select that takes a lambda using an index parameter as well as the entity:

int index = dbContext
  .User
  .OrderByDescending(u => u.Age)
  .Select((user, index) => new {user, index})
  .First(x => x.user == currentUser)
  .index;

我的目标是获取从起始索引到另一个索引的一系列记录

my goal is to get a range of record from a start index to another index

因此，如果您想在未达到特定记录时跳过，为什么不这样做呢?

So if you want to skip while you haven't reached a particular record, why not just do exactly that:

dbContext
  .User
  .SkipWhile(x => x != currentUser)
  .Take(30);

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