具有语句正文的lambda表达式无法转换为nopCommerce中的表达式树 [英] A lambda expression with a statement body cannot be converted to an expression tree in nopCommerce

问题描述

我尝试在nopCommerce 3.0中创建一个linq连接查询。我在linq中加入两个表，并成功写入

I try to create a linq join query in the nopCommerce 3.0. i join two table in linq and write

代码。但是visual studio intellicence显示错误，如

the code successfully. but the visual studio intellicence shows the error like

具有语句正文的lambda表达式无法转换为表达式树

请参阅我的代码

 var roles = _customerEventRoleRepository.Table.Where(c => c.EventId == selevent)
                   .Join
                   (
                      _customerRepository.Table,
                      cev => cev.CustomerId, c => c.Id,
                      (cev, c) =>
                      {                             
                          var cust = new CustomerEventRolesModel();

                          cust.Id = cev.Id;
                          cust.CustomerId = c.Id;
                          cust.Customer = c.Email;
                          cust.ContactName = c.GetAttribute<string>(SystemCustomerAttributeNames.FirstName);
                          cust.CompanyName = c.GetAttribute<string>(SystemCustomerAttributeNames.Company);
                          cust.Speaker = cev.IsSpeaker;
                          cust.Sponsor = cev.IsSponser;

                          return cust;
                      }
                    ).OrderBy(cev => cev.Customer).ToList();

但错误显示

请帮助

推荐答案

错误信息正是说明了什么。你有一个lambda表达式。它有一个声明机构。具有语句正文的lambda表达式无法转换为表达式树。但是加入需要使用表达式树与EF配合使用。你应该尝试用一个没有body的lambda表达式来替换你所拥有的东西，比如：

The error message is exactly what it says. You have a lambda expression. It has a statement body. A lambda expression with a statement body can not be converted to an expression tree. But Join requires an expression tree to use with EF. You should try replacing what you have with a lambda expression that doesn't have a body like:

(cev, c) => new CustomerEventRolesModel {
                Id = cev.Id,
                CustomerId = c.Id
            }

等等。

顺便说一句，

ContactName = c.GetAttribute<string>(SystemCustomerAttributeNames.FirstName)

将无法使用EF 。期。你更好地想出别的东西。

will NOT work with EF. Period. You better figure something else out.

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