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SQL Joins in Entity Framework

Justin
Justin asked
on
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Last Modified: 2018-02-21
I am new to much of the .net entity framework and have been trying to understand how to do joins on data. I am used to using sql joins in ADO but it appears that is a thing of the past. If there is a better way to join tables, specifically on text fields with out a FK that would be great.

I have two different classes for the data:

public class App{
public int ID {get; set;}
public string Name {get; set;}
public string Location1 {get; set;}
public string Location2 {get; set;}
public string Location3 {get; set;}
}

public class Location{
public  LocationID {get; set;}
public string Location {get; set;}
public string Site
}

and i am trying to join the tables by:
public list<App> AppList {get; set;}
var querry = (from a in _Context.App join l in _Context.Location on a.Location1 equals l.Location OR a.Location2 equals l.Location OR a.Location3 equals l.Location
select new { a.Name, l.Site}).ToList();
AppList = querry;


Thank you for any direction you could provide.
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Commented:
Alternatively, you could define your own join method (I renamed your class to LocationX because you cannot have a property with the same name as the class):
    public static class LinqMethods
    {
        public static IEnumerable<T> Join<T>(this IEnumerable<App> apps, IEnumerable<LocationX> locations,
                                            Func<App,App> appSelector,Func<LocationX,LocationX> locationSelector,
                                            Func<App,LocationX,T> resultSelector)
        {
            foreach (var a in apps.Select(appSelector))
            {
                foreach (var l in locations.Select(locationSelector))
                {
                    if (a.Location1 == l.Location || a.Location2 == l.Location || a.Location3 == l.Location)
                    {
                        yield return resultSelector(a, l);
                    }
                }
            }
        }
    }

Open in new window

to join on the object themselves in Linq:
var querry = (from a in _Context.App
              join l in _Context.Location on a equals l
              select new { a.Name, l.Site });

Open in new window

Author

Commented:
Thank you for helping

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