为什么在关系的多对一方向（C＃EF）中，我总是得到空/空数据，而在相反的方向上，它仍然可以正常工作？

Question

Example:

public Tim getTim(int userID) 
{
    TimUsers timUser  = _ctx.TimUser.FirstOrDefault(c => c.ID == userID);
    return _ctx.Times.FirstOrDefault(c => c.ID == timUser.tim.ID);
}

and model (code first) sample:

public class TimUsers
{
    public int ID { get; set; }
    ...

    public virtual Tim time {get;set;}
}

public class Tim 
{
    public int ID { get; set; }
    ...

    public virtual ICollection<TimeUsers> timeUsers { get; set; }
}

I'm 100% sure that a relation between TimeUser and Tim exist becouse this method give me a list of timeUser :

public IQueryable<TimeUsers> GetTimeUsersByTime(int TimeId) 
{
    return _ctx.TimeUser
               .Where(c => c.tim.ID == TimeId)
               .AsQueryable();

}

I'm sorry for syntax error but I wrote this sample without debbuging. Thanks for help.

Answer 1

You need to include the child:

var timeWithChildren = _ctx.Times.Include(t => t.time).FirstOrDefault(c => c.ID == timUser.tim.ID); 

https://msdn.microsoft.com/en-us/data/jj574232.aspx