如何使用动态OR语句构建Linq查询? [英] How can I build Linq query with dynamic OR statements?

问题描述

以下代码:

var dynamicQuery = from a in _context.Users select a;
string[] args = new string[] { "aa", "bb", "cc" };
foreach (string word in args)
    dynamicQuery = dynamicQuery.Where(x => x.Name.Contains(word));
return dynamicQuery.ToList();

允许我使用动态列表的 AND 表达式创建Linq查询.

Will allow me to create a Linq query with a dynamic list of AND expressions.

但是假设我只想使用动态列表的 OR 表达式来做到这一点?

But suppose I wanted to do the same, only with a dynamic list of OR expressions?

推荐答案

您根本不需要循环:

return _context.Users.Where(x => args.Any(word => x.Name.Contains(word)));

更一般而言，您可以使用:

More generally, you can use:

Func<User, bool> predicate = user => false;
foreach (var item in items)
{
    var predicateCopy = predicate;
    predicate = user => predicateCopy(user) || someOtherCondition;
}
return query.Where(predicate);

这将导致非常深的堆栈(一个代表调用另一个代表另一个，以此类推).在特定情况下允许您使用Any的情况，通常这是一种更好的方法.

This will end up with quite deep stacks (with one delegate calling another calling another etc). Where the specific situation allows you to use Any, that would usually be a better approach.

我希望Any在大多数情况下都可以工作，在这些情况下您可能需要匹配的项目集合...非Any方法适用于在某些情况下，年龄在18岁以上的人都可以...在某些情况下，姓氏以"G"开头的任何人都是合适的，等等.

I would expect Any to work in most situations where you've got a collection of items to potentially match against... the non-Any approach is approprate for "in some situations, anyone over 18 is fine... in some situations anyone with a last name beginning with "G" is appropriate, etc.

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