在 Entity Framework Core 中使用动态过滤器 [英] Using dynamic filters with Entity Framework Core

问题描述

我正在开发一个使用 Entity Framework Core 的应用程序(.Net Core 3.1、C# 8).

I'm developing an application (.Net Core 3.1, C# 8) that is using Entity Framework Core.

我想用多个过滤选项过滤一个表格.

I would like to filter a table with several filtering options.

我在 JSON 中获取过滤条件，并将其反序列化为一个对象.我想编写一个 where LINQ 查询，它将根据这些动态过滤选项过滤表.

I'm getting the filter conditions in JSON and I'm deserializing it into an object. I want to write a where LINQ query which will filter the table based on those dynamic filtering options.

问题是我需要使用许多选项和组合来管理过滤.

The twist is I need to manage the filtering with many options and combinations.

• 您可以过滤market、country、vendor，其余的过滤选项将为null.
• 您想过滤country 和vendor 那么market 将为null 以及其余的过滤器选项.

• You can filter for the market, country, vendor and the rest of the filter options will be null.
• You would like to filter for country and vendor then the market will be null and also the rest of the filter options.

我正在查询一个巨大的表，因此编写一个完全转换为 SQL 的查询非常重要.

I'm querying a huge table, so it is important to write a query which translates fully into SQL.

以下代码无法正常工作.我正在寻找可以解决此问题的类似方法:

The following code is not working properly. I'm looking for something similar that can solve this issue:

var filters = new demoFilterEntity()
{
      Market = new List<string>() { "LAT", "NAM" }
};

var filteredData = demoMainRepository.GetAll().Where(x =>
      x.Market != null && (filters.Market != null ? filters.Market.Contains(x.Market) : false) &&
      x.Country != null && (filters.Country != null ? filters.Country.Contains(x.Market) : false)).ToList();

我很感激有关如何解决此问题并动态管理过滤的建议.

I would appreciate suggestions on how I can get through this and manage the filtering dynamically.

推荐答案

如果您只有 AND 条件，您只需链接 Where 子句即可:

If you have only AND conditions you can do it with just chaining Where clauses:

var query = demoMainRepository.GetAll().Where(x => x.Market != null); 
if(filters.Market != null)
{
    query = query.Where(x => filters.Market.Contains(x.Market));
}
...
var filteredData = query.ToList();

另外，正如 @Lajos Arpad 所说，也许您需要考虑组合字段空检查(即 x.Market != null) 与过滤器检查:

Also as @Lajos Arpad said maybe you need to consider combining fields null checks (i.e. x.Market != null) with the filters checks:

var query = demoMainRepository.GetAll(); 
if(filters.Market != null)
{
    query = query.Where(x =>  x.Market != null && filters.Market.Contains(x.Market));
}
...
var filteredData = query.ToList();

这篇关于在 Entity Framework Core 中使用动态过滤器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！