LinqTOEntities差异beteen存在并包含 [英] LinqTOEntities difference beteen Exists and contains

问题描述

在contains上使用exists

var s = new int[] { 1, 2, 3, 4, 5 };
dbset.where(x => s.contains(x.id);

或

var s = new int[] { 1, 2, 3, 4, 5 };
dbset.Where(x => s.Exists(y => x.id));

推荐答案

1. 存在是List<T>的方法，没有数组或IEnumerable<T>扩展名上的此类方法.
2. 此方法用法的正确语法为x => s.Exists(y => y == x.id)(您应传递谓词，即返回布尔值的方法)
3. 区别是-Linq to Entities支持Contains，不支持Exists.

1. Exists is a method of List<T>, there is no such method on array or IEnumerable<T> extensions.
2. Correct syntax of usage of this method is x => s.Exists(y => y == x.id) (you should pass predicate, i.e. method which returns boolean)
3. The difference is - Contains supported by Linq to Entities, Exists is not supported.

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