在实体框架使用动态where子句 [英] Using dynamic where clauses in Entity Framework

问题描述

我试图重新设计使用Raptier，最初建立了一个数据访问层。接受where子句作为参数Raptier generats方法，在一个存储过程进行传递。我真的需要保留现有mesthos签名，所以我的新DAL需要接受where子句为好。我想用越涨最新数据访问技术和工艺，因此想使用实体框架的.NET 4.0。

I am trying to re-design a data access layer that was originally built using Raptier. Raptier generats methods that accept a where clause as a parameter to be passed in to a stored proc. I really need to retain the existing mesthos signatures, so my new DAL needs to accept where clauses as well. I want to use the more up-to-date data access technologies and techniques, so was thinking about using Entity Framework from .Net 4.0.

然而，它不看起来像我可以接受动态where子句没有实施一些激烈的reoutines他们解析为兰巴表达式。有什么我已经错过了？难道我的运气与实体框架？

However, it doesn't look like I can accept dynamic where clauses without implementing some intense reoutines to parse them into lamba expressions. Is there something I've missed? Am I out of luck with Entity Framework?

谢谢，
马克

推荐答案

进来两种念头。

1）。 动态LINQ ，它允许您定义，操作员为字符串。

1). Dynamic LINQ, which allows you to define where operators as strings.

var result = Northwind.Products
    .Where("CategoryId=2 And UnitPrice>3")
    .OrderBy("SupplierId");

2）。使用的东西作为 EntityFilter< T> （参见代码这里），它允许你定义这样的过滤器：

2). Use something as the EntityFilter<T> (see code here), which allows you to define a filter like this:

IEntityFilter<Person> entityFilter =
    from person in EntityFilter<Person>.AsQueryable()
    where person.Name.StartsWith("a")
    where person.Id < 100
    select person;

您可以提供 IEntityFilter<人> 一个企业的方法，将能够过滤查询：

You can supply the IEntityFilter<Person> to a business method that will be able to filter that query:

public static Person[] GetAllPersons(
    IEntityFilter<Person> filter)
{
    using (var db = ContextFactory.CreateContext())
    {
        IQueryable<Person> filteredList =
            filter.Filter(db.Persons);

        return filteredList.ToArray();
    }
}

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