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Seed the Database with Test Data

Posted on 2013-11-23
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Last Modified: 2014-01-27
I was wondering if I could get an explanation of the few line bellow from this code that I found from this tutorial...http://www.asp.net/mvc/tutorials/getting-started-with-ef-using-mvc/creating-a-more-complex-data-model-for-an-asp-net-mvc-application

students.ForEach(s => context.Students.AddOrUpdate(p => p.LastName, s));

Explantion?
--------------------------

  var courses = new List<Course>
            {
                new Course {CourseID = 1050, Title = "Chemistry",      Credits = 3,
                  DepartmentID = departments.Single( s => s.Name == "Engineering").DepartmentID,
                  Instructors = new List<Instructor>()
                },


Explantion?
--------------------------



    AddOrUpdateInstructor(context, "Chemistry", "Kapoor");
            AddOrUpdateInstructor(context, "Chemistry", "Harui");


  StudentID = students.Single(s => s.LastName == "Barzdukas").ID,
                    CourseID = courses.Single(c => c.Title == "Chemistry").CourseID,
                    Grade = Grade.B  



Explantion?
--------------------------
foreach (Enrollment e in enrollments)
            {
                var enrollmentInDataBase = context.Enrollments.Where(
                    s =>
                         s.Student.ID == e.StudentID &&
                         s.Course.CourseID == e.CourseID).SingleOrDefault();
                if (enrollmentInDataBase == null)
                {
                    context.Enrollments.Add(e);
                }
            }
            context.SaveChanges();
        }

        void AddOrUpdateInstructor(SchoolContext context, string courseTitle, string instructorName)
        {
            var crs = context.Courses.SingleOrDefault(c => c.Title == courseTitle);
            var inst = crs.Instructors.SingleOrDefault(i => i.LastName == instructorName);
            if (inst == null)
                crs.Instructors.Add(context.Instructors.Single(i => i.LastName == instructorName));
        }
    }



Explantion?
--------------------------
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Question by:yguyon28
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3 Comments
 
LVL 9

Expert Comment

by:QuinnDex
ID: 39672481
the tutorial explains this code and what it is doing, and why you have created an empty list for Instructors.

Read it again go through the code, come back with more specific questions on what you dont understand.
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Author Comment

by:yguyon28
ID: 39672858
I'm not really sure how to understand the sentence bellow....
          students.ForEach(s => context.Students.AddOrUpdate(p => p.LastName, s));
0
 
LVL 9

Accepted Solution

by:
QuinnDex earned 1500 total points
ID: 39682882
works in context with other fields, if it exists already then performs update else adds a new record.
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