如何使用Linq将数据联接到实体和WCF数据服务? [英] How can I join data with Linq to Entities and WCF Data Services?

问题描述

我有4个与以下内容相关的实体:

I have 4 entities that are related as follows:

LocalAgency<-0..1----1->Agency<-0..1----1->Organization<-0..1----1->Customer

换句话说，LocalAgency具有一个相关的Agency，依此类推.使用Entity Framework(包含导航属性以细读那些关系)来建立数据模型，并且将WCF DataService设置为将这些数据提供给客户.

In other words, a LocalAgency has one related Agency, etc. The data model is set up using Entity Framework (containing navigation properties to peruse those relationships), and a WCF DataService is set up to provide that data to clients.

在使用DataService的客户端上，我试图基于客户名称返回对本地代理商的查询，但是还没有找到支持该简单查询的方法.

On the client side that consumes the DataService, I'm trying to return a query of local agencies based on a customer name, but haven't found a supported way to formulate this simple query.

我尝试的第一种方法是使用Expand，如下所示:

The first method I tried was using Expand as follows:

var items = (from i in Context.LocalAgencies.Expand("Agency").Expand("Organization").Expand("Customer")
             where (String.IsNullOrEmpty(CustomerName) || i.Agency.Organization.Customer.CustomerName.Contains(CustomerName))
             select i).Skip(StartIndex).Take(PageSize).ToList<LocalAgency>();

如果"join"仅深1级，则此方法有效，但这无法获得导航属性的导航属性.

This approach works if the "join" is only 1 level deep, but this fails to get navigation properties of navigation properties.

然后我尝试了join如下:

var items = (from localAgency in Context.LocalAgencies
             join agency in Context.Agencies on localAgency.CustomerID equals agency.CustomerID
             join organization in Context.Organizations on localAgency.CustomerID equals organization.CustomerID
             join customer in Context.Customers on localAgency.CustomerID equals customer.CustomerID
             where (String.IsNullOrEmpty(CustomerName) || customer.CustomerName.Contains(CustomerName))
             select localAgency).Skip(StartIndex).Take(PageSize).ToList<LocalAgency>();

但是，在这种情况下不支持join.

But, join is not supported in this instance.

然后我尝试使用Except方法，如下所示:

I then tried using the Except method as follows:

IQueryable<LocalAgency> items = Context.LocalAgencies;
items = items.Except(from i in items
                     where (String.IsNullOrEmpty(CustomerName) || i.Agency.Organization.Customer.CustomerName.Contains(CustomerName))
                     select i).Skip(StartIndex).Take(PageSize);

但是，在这种情况下不支持Except.

But, Except is not supported in this instance.

我想念什么?我是否需要在DataService端进行一些设置，以允许沿着定义的导航属性进行简单连接?

What am I missing? Do I need to set up something on the DataService side to allow a simple join along defined navigation properties?

推荐答案

我在Expand上使用了错误的语法.我做了以下事情:

I used the wrong syntax on the Expand. I did the following:

var items = (from i in Context.LocalAgencies.Expand("Agency").Expand("Agency/Organization").Expand("Agency/Organization/Customer")
where (String.IsNullOrEmpty(CustomerName) || i.Agency.Organization.Customer.CustomerName.Contains(CustomerName))
select i).Skip(StartIndex).Take(PageSize).ToList<LocalAgency>();

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