Question

我有两个表（客户端和电子邮件），一个包含客户的数据，包括一个主电子邮件地址，另一个包含其他电子邮件地址。

我需要从众多电子邮件地址中的一个验证用户，无论是在客户端还是电子邮件表中。我想出了这个SQL语句可以正常工作：

set @email = 'client@domain.com';
select c1.credits > 0 as Allowed, c1.Email as MainEmail from 
customers c1 inner join (select ClientId,  Email FROM customers WHERE 
Email=@email union all select ClientId, Email FROM emails WHERE Email=@email) e1 
on c1.ClientId = e1.ClientId;

如何使用基于方法的语法在LINQ to Entities中编写此查询？

Answer 1

如果我理解正确，

客户可能会或可能不会在emails表格中收到电子邮件（附加）。此外，客户在emails表中还有多个附加电子邮件条目。如下所示

List<Customer> customers = new List<Customer> 
{ 
    new Customer { ClientId = 1, Email = "client1@domain.com", Credits = 2 },
    new Customer { ClientId = 2, Email = "client2@domain.com", Credits = 1 },
    new Customer { ClientId = 3, Email = "client3@domain.com", Credits = 1 },
};

List<Emails> emails = new List<Emails> 
{ 
    new Emails { ClientId = 1, Email = "client1-2@domain.com" },
    new Emails { ClientId = 1, Email = "client1-3@domain.com" },
    new Emails { ClientId = 2, Email = "client2-1@domain.com" },
};

在这种情况下，请使用以下查询完成此操作，

var result = from c in customers
             let _emails = emails.Where(e => c.ClientId == e.ClientId).Select(t => t.Email)
             where c.Email == "client3@domain.com" || _emails.Contains("client3@domain.com")
             select new
             {
                 Allowed = c.Credits > 0,
                 MainEmail = c.Email
             };

我希望它可以帮到你。

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