LINQ to SQL multiple tables left outer join

Here is how left outer joins are implemented with LINQ. You should use GroupJoin (join...into syntax):

from d in context.dc_tpatient_bookingd
join bookingm in context.dc_tpatient_bookingm
     on d.bookingid equals bookingm.bookingid into bookingmGroup
from m in bookingmGroup.DefaultIfEmpty()
join patient in dc_tpatient
     on m.prid equals patient.prid into patientGroup
from p in patientGroup.DefaultIfEmpty()
// ... other joins here
where d.processid == 6 &&
      ((m.branchId == 1 && d.DestinationBranchID == 0) ||
       (d.DestinationBranchID == 1 && d.sendstatus == "R"))
// ... other conditions here
orderby d.priority descending, m.bookingid
select new {
   d.bookingid,
   d.labid,
   d.processid,
   p.prid,
   p.prno,
   m.bookingid // need for grouping
} into x
group x by x.bookingid into g
select g

This query joins three tables. You can join the rest of the tables the same way.

This is multiple left join sample with null checking (preventing null reference exception). Thnx to Nick!

void Main()
{
    var data = DataAccess.GetData();
    var res = 
        from m in data.Movies
        join ma in data.MovieActor on m.Id equals ma.MovieId into mma
        from ma in mma.DefaultIfEmpty()
        join p in data.People on (ma == null ? 0 : ma.ActorId) equals p.Id into pma
        from p in pma.DefaultIfEmpty()
        orderby m.Name
        select new {
            Movie = m.Name,
            Actor = p != null ? p.Name + " as " + ma.Name : ""
        };
    foreach (var el in res)
    {
        Console.WriteLine($"{el.Movie} - {el.Actor}");
    }
}

public class DataAccess
{
    public static Data GetData()
    {
        var list = new Data
        {
            Movies = new List<Movie>{
             new Movie{ Id = 1, Name= "Raiders of the Lost Ark", Year = 1981},
             new Movie{ Id = 2, Name= "Blade Runner", Year = 1982},
             new Movie{ Id = 3, Name= "Star Wars: Episode IV - A New Hope", Year = 1977},
             new Movie{ Id = 4, Name= "Total Recall", Year = 1990},
             new Movie{ Id = 5, Name= "The Fugitive", Year = 1993},
             new Movie{ Id = 6, Name= "Men in Black", Year = 1997},
             new Movie{ Id = 7, Name= "U.S. Marshals", Year = 1998},
             new Movie{ Id = 8, Name= "Batman", Year = 1989},
             new Movie{ Id = 9, Name= "A Few Good Men", Year = 1992},
             new Movie{ Id = 10, Name= "Tropic Thunder", Year = 2008},
             new Movie{ Id = 11, Name= "Minority Report", Year = 2002},
             new Movie{ Id = 12, Name= "The Fifth Element", Year = 1997},
             new Movie{ Id = 13, Name= "District 9", Year = 2009},
             new Movie{ Id = 14, Name= "12 Monkeys", Year = 1995},
            },
            People = new List<Person>{
                new Person{ Id = 1, Name = "Harrison Ford"},
                new Person{ Id = 2, Name = "Tommy Lee Jones"},
                new Person{ Id = 3, Name = "Will Smith"},
                new Person{ Id = 4, Name = "Michael Keaton"},
                new Person{ Id = 5, Name = "Will Smith"},
                new Person{ Id = 6, Name = "Jack Nicholson"},
                new Person{ Id = 7, Name = "Tom Cruise"}
            },
            MovieActor = new List<MovieActor>{
                new MovieActor{ MovieId = 1, ActorId = 1, Name = "Indy"},
                new MovieActor{ MovieId = 2, ActorId = 1, Name = "Rick Deckard"},
                new MovieActor{ MovieId = 3, ActorId = 1, Name = "Han Solo"},
                new MovieActor{ MovieId = 5, ActorId = 1, Name = "Dr. Richard Kimble"},
                new MovieActor{ MovieId = 5, ActorId = 2, Name = "Samuel Gerard"},
                new MovieActor{ MovieId = 6, ActorId = 2, Name = "Kay"},
                new MovieActor{ MovieId = 7, ActorId = 2, Name = "Samuel Gerard"},
                new MovieActor{ MovieId = 6, ActorId = 3, Name = "Jay"},
                new MovieActor{ MovieId = 8, ActorId = 4, Name = "Batman / Bruce Wayne"},
                new MovieActor{ MovieId = 8, ActorId = 6, Name = "Joker / Jack Napier"},
                new MovieActor{ MovieId = 9, ActorId = 6, Name = "Col. Nathan R. Jessep"},
                new MovieActor{ MovieId = 9, ActorId = 7, Name = "Lt. Daniel Kaffee"},
                new MovieActor{ MovieId = 10, ActorId = 7, Name = "Les Grossman"},
                new MovieActor{ MovieId = 11, ActorId = 7, Name = "Chief John Anderton"}
            }

        };
        return list;
    }
}

public class Data
{
    public List<Movie> Movies = new List<Movie>();
    public List<Person> People = new List<Person>();
    public List<MovieActor> MovieActor = new List<MovieActor>();
}

public class Person
{
    public int Id { get; set; }
    public string Name { get; set; }
}

public class Movie
{
    public int Id { get; set; }
    public string Name {get; set;}
    public int Year { get; set; }
}

public class MovieActor
{
    public int MovieId { get; set; }
    public int ActorId { get; set; }
    public string Name { get; set; } // appearance as
}