如何使用LINQ链接OR子句? [英] How to chain OR clauses, with LINQ?

问题描述

我有一种情况，我需要使用LINQ构建SQL查询，其中包括可变数量的OR子句.我正在编写一个函数，该函数将基于某些输入来构建查询.函数定义看起来类似于...

I've got a scenario where I need to build a SQL query, using LINQ, that includes a variable amount of OR clauses. I'm writing a function that will build the query based on some input. The function definition looks something similar to ...

function BuildQuery(ICollection<ColumnsThatNeedToBeTrue> columns)
{
  ...
}

因此，我得到了一组需要检查是否为true的列，并且该检查需要使用OR子句.

So, I'm given a collection of columns that I need to check for true, and the check needs to use OR clauses.

如果columns数组包含A和B，则需要查询以检查列A是true还是列B是true.

If the columns array contains A and B, I'd need the query to check if column A is true OR column B is true.

如果columns数组包含A，B和C，则需要查询并检查A或B或C是否为真.

If the columns array contains A, B and C, I'd need to query and check if A OR B OR C are true.

我不知道如何在单个Where中完成所有这些操作，因为我不知道一种逐步处理其他||子句的方法.我不确定如何根据输入数组在下面添加其他OR检查.

I don't know how to do this all within a single Where, because I don't know of a way to progressively tack on additional || clauses. I'm not sure how I'd include additional OR checks in the below, based on the input array.

var query = entities.Where(m => m.A == true || m.B == true ...)

我无法链接Where函数，每个函数都进行各自的列检查，因为它使用AND子句构建了该查询，并且我需要OR.

I cannot chain Where functions, each for their own column check, because it builds that query using AND clauses and I need OR.

有没有一种使用LINQ建立这样的查询的方法?

Is there a way to build out a query like this, using LINQ?

推荐答案

您可以使用 PredicateBuilder 链接or条件.

var predicate = PredicateBuilder.False<SomeEntity>();

predicate = predicate.Or (p => p.A == true);
if(something)
   predicate = predicate.Or (p => p.B == true);

var query = entities.AsExpandable().Where (predicate); //AsExpandable() for EF

这篇关于如何使用LINQ链接OR子句?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！