I want to apply join into command using a column and a variable value.
我想使用列和变量值将join命令应用于命令。
here's the code (the partial part of the query where I have an issue):
这是代码(我遇到问题的查询的部分部分):
join p in db.user_tests on a.id equals p.test_id into g3
from x3 in g3.DefaultIfEmpty()
This code works, but I also need to filter the db.user_tests by the user_id. I have that user_id in a variable userId inside the function.
此代码有效,但我还需要通过user_id过滤db.user_tests。我在函数内的变量userId中有user_id。
So I decided to write the query as follows:
所以我决定编写如下查询:
join p in db.user_tests on a.id equals p.test_id && userId equals p.user_id into g3
from x3 in g3.DefaultIfEmpty()
But I get "Operator && cannot be applied to operands of type long and bool" error.
但我得到“运算符&&不能应用于long类型和bool类型的操作数”错误。
I tried with equal but it throws several errors.
我尝试平等,但它抛出了几个错误。
I also tried with the two column join, but I use a variable in the comparison so it doesn't work.
我也试过两列连接,但我在比较中使用了一个变量,所以它不起作用。
How can I use the join into with a column comparison and a variable at the same time?
如何将连接同时用于列比较和变量?
1 个解决方案
#1
1
If you want to join on several properties you should use anonymous objects for that:
如果要加入多个属性,则应使用匿名对象:
join p in db.user_tests
on new { a.id, userId } equals new { id = p.test_id, userId = p.user_id } into g3
from x3 in g3.DefaultIfEmpty()
Also make sure that anonymous objects have properties with same types and names.
还要确保匿名对象具有相同类型和名称的属性。
But thus userId is not part of your a object it makes no sense to use that variable as part of join. You can simply join on test_id and use filter by user_id:
但是因此userId不是您对象的一部分,将该变量用作连接的一部分是没有意义的。您可以简单地加入test_id并按user_id使用过滤器:
join p in db.user_tests.Where(x => x.user_id == userId)
on a.id equals np.test_id into g3
from x3 in g3.DefaultIfEmpty()
#1
1
If you want to join on several properties you should use anonymous objects for that:
如果要加入多个属性,则应使用匿名对象:
join p in db.user_tests
on new { a.id, userId } equals new { id = p.test_id, userId = p.user_id } into g3
from x3 in g3.DefaultIfEmpty()
Also make sure that anonymous objects have properties with same types and names.
还要确保匿名对象具有相同类型和名称的属性。
But thus userId is not part of your a object it makes no sense to use that variable as part of join. You can simply join on test_id and use filter by user_id:
但是因此userId不是您对象的一部分,将该变量用作连接的一部分是没有意义的。您可以简单地加入test_id并按user_id使用过滤器:
join p in db.user_tests.Where(x => x.user_id == userId)
on a.id equals np.test_id into g3
from x3 in g3.DefaultIfEmpty()