如何将OData筛选器转换为LINQ表达式? [英] How to transform OData filter to a LINQ expression?

问题描述

我正在尝试从ODataQueryOptions中提取过滤器表达式，以便可以在我的业务逻辑类中使用它.

I'm trying to extract the filter expression from ODataQueryOptions so that I can use it in my business logic class.

public PageResult<Poco> Get(ODataQueryOptions odataQueryOptions)
{
    Expression<Func<Poco, bool>> myExpression = ... // what do i do here?

    var result = _myBusinessLogic.Search(myExpression);
    return new PageResult<Poco>(result, null, null);
}

我看了一下博客，描述了将查询转换为HQL

I took a look at the blog describing translating the query into HQL here and I think (at least I hope) that's an overkill for what I'm trying to do.

我基本上需要以Expression<Func<Poco, bool>>形式获取过滤器表达式.我尝试使用ApplyTo()玩游戏，但我不太明白.任何帮助表示赞赏.

I basically need to get the filter expression in the Expression<Func<Poco, bool>> form. I tried playing with ApplyTo() but I can't quite get it. Any help appreciated.

推荐答案

我们有一个FilterBinder类，它适合您的需求，但是内部很不幸.不过，您可以做一个简单的技巧来掌握$ filter表达式，

We have a FilterBinder class that suits your needs but is internal unfortunately. Nevertheless you could do a simple trick to get hold of the $filter expression,

public static class ODataQueryOptionsExtensions
{
    public static Expression ToExpression<TElement>(this FilterQueryOption filter)
    {
        IQueryable queryable = Enumerable.Empty<TElement>().AsQueryable();
        queryable = filter.ApplyTo(queryable, new ODataQuerySettings());
        return queryable.Expression;
    }
}

就您而言，您可以做到，

In your case, you can just do,

public PageResult<Poco> Get(ODataQueryOptions odataQueryOptions)
{
    Expression<Func<Poco, bool>> myExpression = odataQueryOptions.Filter.ToExpression<Poco>();

    var result = _myBusinessLogic.Search(myExpression);
    return new PageResult<Poco>(result, null, null);
}

请注意，表达式包含的内容更像这样， SOTests.Customer[].Where($it => conditional-expression).因此，您可能必须从lambda中提取该条件表达式.

Notice that the expression contains looks more like this, SOTests.Customer[].Where($it => conditional-expression). So, you might have to extract that conditional expression from the lambda.

这篇关于如何将OData筛选器转换为LINQ表达式?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！