3个表之间的连接
3个表之间的连接
提问于 2019-04-22 20:46:54
我有3个表User，HumanCustomer，CompanyCustomer我想使用LINQ表之间的连接，但我的查询不起作用，它返回null
查询：
var query = (from users in _ctx.Users
join hCustomer in _ctx.HumanCustomers on users.Id equals hCustomer.UserId
join cCustomer in _ctx.CompanyCustomers on users.Id equals cCustomer.UserId
select new
{
users.Id,
users.Mobile,
hCustomer.LastName,
hCustomer.Name,
cCustomer.CompanyName
});
foreach (var item in query)
{
AllCustomerViewModel allCustomer = new AllCustomerViewModel();
if (item.Name != null)
{
allCustomer.UserId = item.Id;
allCustomer.FullName = item.Name + item.LastName;
allCustomer.Mobile = item.Mobile;
Customer.Add(allCustomer);
}
}代码不会输入foreach
我认为问题是使用了两次UserId，因为当我删除
join cCustomer in _ctx.CompanyCustomers on users.Id equals cCustomer.UserId查询运行正确。
回答 2
Stack Overflow用户
发布于 2019-04-23 06:13:16
也许您的问题是您试图迭代的动态变量。
您可以尝试：
foreach (dynamic item in query)或者，通过将查询的开头更新为以下内容，编写类来保存要选择的值：
var query = (from users in _ctx.Users
join hCustomer in _ctx.HumanCustomers on users.Id equals hCustomer.UserId
join cCustomer in _ctx.CompanyCustomers on users.Id equals cCustomer.UserId
select new MyClass
{
Id = users.Id,
Mobile = users.Mobile,
LastName = hCustomer.LastName,
Name = hCustomer.Name,
CompanyName = cCustomer.CompanyName
});Stack Overflow用户
发布于 2019-04-22 21:43:35
you can try this way..
var query = (from users in _ctx.Users
join hCustomer in _ctx.HumanCustomers on users.Id equals hCustomer.UserId
join cCustomer in _ctx.CompanyCustomers on users.Id equals cCustomer.UserId
select new
{
Id = users.Id,
Mobile = users.Mobile,
LastName = hCustomer.LastName,
Name = hCustomer.Name,
CompanyName = (cCustomer == null ? "" : cCustomer .CompanyName)
});页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/55794675
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