EF Basic 26: Add Entity Graph

Add Entity Graph using DbContext

Adding entity graph with all new entities is a simple task. We can use DbSet.Add() method to attach a whole entity graph to the context and set all the entity's states to Added as we have seen in the previous section.

The following example adds a student entity graph in disconnected mode, using the DbSet.Add() method which marks the added state to all the entities:

//Create student in disconnected mode
Student newStudent = new Student() { StudentName = "New Single Student" };
            
//Assign new standard to student entity
newStudent.Standard = new Standard() { StandardName = "New Standard" };
            
//add new course with new teacher into student.courses
newStudent.Courses.Add(new Course() { CourseName = "New Course for single student", Teacher = new Teacher() { TeacherName = "New Teacher" } });

using (var context = new SchoolDBEntities())
{
    context.Students.Add(newStudent);
    context.SaveChanges();

    Console.WriteLine("New Student Entity has been added with new StudentId= " + newStudent.StudentID.ToString());
    Console.WriteLine("New Standard Entity has been added with new StandardId= " + newStudent.StandardId.ToString());
    Console.WriteLine("New Course Entity has been added with new CourseId= " + newStudent.Courses.ElementAt(0).CourseId.ToString());
    Console.WriteLine("New Teacher Entity has been added with new TeacherId= " + newStudent.Courses.ElementAt(0).TeacherId.ToString());
}

Output:

New Student Entity has been added with new StudentId= 14 
New Standard Entity has been added with new StandardId= 6
New Course Entity has been added with new CourseId= 7
New Teacher Entity has been added with new TeacherId= 9

This executes the following DDL statements to the database:

exec sp_executesql N'INSERT [dbo].[Standard]([StandardName], [Description])
VALUES (@0, NULL)
SELECT [StandardId]
FROM [dbo].[Standard]
WHERE @@ROWCOUNT > 0 AND [StandardId] = scope_identity()',N'@0 varchar(50)',@0='New Standard'
go

exec sp_executesql N'INSERT [dbo].[Student]([StudentName], [StandardId])
VALUES (@0, @1)
SELECT [StudentID]
FROM [dbo].[Student]
WHERE @@ROWCOUNT > 0 AND [StudentID] = scope_identity()',N'@0 varchar(50),@1 int',@0='New Single Student',@1=61
go

exec sp_executesql N'INSERT [dbo].[Teacher]([TeacherName], [StandardId])
VALUES (@0, NULL)
SELECT [TeacherId]
FROM [dbo].[Teacher]
WHERE @@ROWCOUNT > 0 AND [TeacherId] = scope_identity()',N'@0 varchar(50)',@0='New Teacher'
go

exec sp_executesql N'INSERT [dbo].[Course]([CourseName], [Location], [TeacherId])
VALUES (@0, NULL, @1)
SELECT [CourseId]
FROM [dbo].[Course]
WHERE @@ROWCOUNT > 0 AND [CourseId] = scope_identity()',N'@0 varchar(50),@1 int',@0='New Course for single student',@1=93
go

exec sp_executesql N'INSERT [dbo].[StudentCourse]([StudentId], [CourseId])
VALUES (@0, @1)
',N'@0 int,@1 int',@0=43,@1=72
go

Thus, there is no difference when you add a single entity or entity graph in disconnected or connected scenario. Make sure that all the entities are new.

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Learn how to update entity graph in disconnected scenario in the next section.