Linq Extension method for Join
If I understand your question, you're trying to do a conditional on a joined model?
var query = db.Users.Where(x => x.Addresses.Where(y => y.Value >= yourValue).Any());
That will return all users who have a property value greater than yourValue
. If you need to return the addresses with the query, you can just add Include
to your query. For example:
query.Include(x => x.Addresses);
You don't need to manually do that Join
that you have in your example.
Jeff
Updated on June 04, 2022Comments
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Jeff almost 2 years
I am in the process of learning LINQ, ASP.NET, EF, and MVC via online video tutorials. I would love some help understanding Joins in LINQ extension method syntax.
For simplification, I have two tables (these map to a SQL DB):
User Table: public int userID{get;set;} public string firstName{get;set;} ... Address public int ownerID{get;set;} public int value{get;set;} public string Nickname{get;set;} public string street{get;set;} public string zip{get;set;} ...
Let's say I want to find all the property that a particular user owns. I believe I can do something like this:
var test = db.User .Join(db.Address, user => user.userID, add => add.ownerID, (user, add) => new { user, add }); Source: http://byatool.com/c/linq-join-method-and-how-to-use-it/
This should be equivalent to
SELECT * FROM User a JOIN Address b on a.userID = b.ownerID
Please confirm that this is correct.
Now, what if I wanted to find all property that a particular user owns that has a
value greater than x
. Let's take it a step further and say x is a result from another LINQ query. How do I force execution ofx
inside of a second query? Do I even have to consider this, or will LINQ know what to do in this case?Thanks
EDIT: When I try to use the result of a query as a parameter in another, I am required to use a greedy operator to force execution. Many people like to use
.Count()
or.ToList()
. I only expectx
(from example above) to return 1 string by using.Take(1)
. If I appendToList()
to the end of my first query, I am required to use x[0] in my second query. This seems like a messy way to do things. Is there a better way to force execution of a query when you know you will only have 1 result?