Say we have a project with this entities:
class User
{
public Guid Id { get; set; }
public List<Message> Messages { get; set; }
...
}
class Message
{
public Guid Id { get; set; }
public string Message { get; set; }
}
Now consider a scenerio where i want to get all the messages that a certain user posted, how can one achieve this without pulling the user information aswell? (without using the context.Users.Include(...) ) ? I know that the entity framework creates a column in the Message table that holds the Id of the user that posted this message, but how can i have an access to this value? as it is not a property in my original class.
You can add a navigation property into the Message class:
public class Message
{
public Guid Id { get; set; }
public string Message { get; set; }
public virtual User User { get; set; }
}
And then query your context like this:
var userMessages = context.Messages
.Where(m => m.User.Id == 5);
This is the tidier way of doing it. Alternatively, you could start with the user, but this is a little more awkward:
var userMessages = context.Users
.Where(u => u.Id == 5)
.SelectMany(u => u.Messages);
Both methods will ultimately produce the similar SQL, something like this:
SELECT [Extent1].[Column1],
[Extent1].[Column2],
[Extent1].[Column3]
FROM [dbo].[Messages] AS [Extent1]
WHERE 5 = [Extent1].[UserId]
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