static void Main(string[] args)
{
//good for desktop applicatios wpf etc...
//var context = new PlutoContext();
//var authors = context.Authors.ToList();// A Dictionary for Grids or comboBoxes
//var author = context.Authors.Single(a => a.Id == 1);
//var Course = new Course
//{
// Name = "New Course2",
// Description = "New Description2",
// FullPrice = 20.95f,
// Level = 1,
// Author = author
//};
//context.Courses.Add(Course);
//context.SaveChanges();
// Better for MVC and webApplications
var context = new PlutoContext();
var Course = new Course
{
Name = "New Course 3",
Description = "New Description 3",
FullPrice = 20.95f,
Level = 1,
AuthorId = 1
};
context.Courses.Add(Course);
context.SaveChanges();
}
private static void AddingObjects()
{
var context = new PlutoContext();
// Method 1, Using an existing object in context
//var authors = context.Authors.ToList();
//var author = context.Authors.Single(a => a.Id == 1);
// Method 3
var author = new Author()
{
Id = 1, Name = "Kubing"
};
context.Authors.Attach(author);
var course = new Course()
{
Name = "New Course",
Description = "New Description",
FullPrice = 19.95f,
Level = 1,
//Author = author // Method 1
//AuthorId = 1 // Method 2, Using foreign key properties
Author = author // Method 3, not recommend
};
context.Courses.Add(course);
context.SaveChanges();
}
static void Main(string[] args)
{
var context = new PlutoContext();
var course = context.Courses.Find(10); //same for Single(c=>c.Id == 4)
course.Name = "New Name";
course.Description = "Updating by me";
course.AuthorId = 2;
context.SaveChanges();
}
private static void UpdatingObjects()
{
var context = new PlutoContext();
var course = context.Courses.Find(4); // Single(c => c.Id == 4)
course.Name = "New Name";
course.AuthorId = 2;
context.SaveChanges();
}
private static void ExampleRemovingObjects()
{
var context = new PlutoContext();
// With cascade delete;
var course = context.Courses.Find(10);
context.Courses.Remove(course);
context.SaveChanges();
// can see in SQL Profiler;
// ------------------------------------
// Without cascade delete;
// This will throw an exception (from SQL);
//var author = context.Authors.Find(6);
//context.Authors.Remove(author);
// So in this case we need to explicitly delete these courses first, and then delete the author;
var author = context.Authors.Include(a => a.Courses).Single(a => a.Id == 7);
// Use RemoveRang if you want to remove a list of objects - it accepts an IEnumerable object,
// so this way you don't have to use a foreach block and call the remove method on each object;
context.Courses.RemoveRange(author.Courses);
context.Authors.Remove(author);
context.SaveChanges();
// can se in SQL Profiler;
// -----------------------
// Best Praticles
// Prefer local deletes to physical deletes
// author.IsDeleted = true;
}
private static void RemovingObjects()
{
var context = new PlutoContext();
//var course = context.Courses.Find(6);
//context.Courses.Remove(course);
// Cascade on delete
var author = context.Authors.Include(a => a.Courses).Single(a => a.Id == 2);
context.Courses.RemoveRange(author.Courses);
context.Authors.Remove(author);
context.SaveChanges();
}
private static void ExampleUpdatingObjects()
{
var context = new PlutoContext();
// The Find method we use it to look up objects by their primary key,
// it's a short way of writing this: Single(c => c.Id == 4);
// and if your records have composite primary keys, you can pass multiple values like this:
//var course = context.Courses.Find(4, 1, 2);
var course = context.Courses.Find(4);
course.Name = "Javascript: Understanding the Weird Parts 2";
course.AuthorId = 2;
context.SaveChanges();
}
public static void AddCourse_MVC(PlutoContext context)
{
var author = context.Authors.Single(a => a.Id == 1);
var course = new Course
{
Name = "New course 3",
Description = "Description for new course 3",
FullPrice = 19.95f,
Level = 1,
AuthorId = 1
};
context.Courses.Add(course);
context.SaveChanges();
}
public static void AddCourse(PlutoContext context)
{
var course = new Course
{
Name = "New course",
Description = "Description for new course",
FullPrice = 19.95f,
Level = 1,
Author = new Author {
Id = 1, Name = "Mosh Hamedani"
}
};
context.Courses.Add(course);
context.SaveChanges();
}
static void Main(string[] args)
{
///Simple delete
//var context = new PlutoContext();
//var course = context.Courses.Find(10); //same for Single(c=>c.Id == 4)
//context.Courses.Remove(course);
//context.SaveChanges();
//Recursive dele
var context = new PlutoContext();
var author = context.Authors.Include(a => a.Courses).Single(a => a.Id == 6); //select all couses of author
context.Courses.RemoveRange(author.Courses); //remove first all couses
context.Authors.Remove(author); // after revove Author
context.SaveChanges(); //final apply al changes
}
public static void AddCourse_AuthorNotInContext(PlutoContext context)
{
var author = new Author()
{
Id = 1, Name = "Mosh Hamedani"
};
context.Authors.Attach(author);
var course = new Course
{
Name = "New course 4",
Description = "Description for new course 4",
FullPrice = 19.95f,
Level = 1,
Author = author
};
context.Courses.Add(course);
context.SaveChanges();
}
private static void ExampleAddingObjects()
{
var context = new PlutoContext();
#region initial code
var course = new Course
{
Name = "New Course",
Description = "New Description",
FullPrice = 19.95f,
Level = 1,
Author = new Author {
Id = 1, Name = "Mosh Hamedani"
} // here we're instantiating a new author, because of that it will created
// a new author on database; the change tracker sees this as a new object;
// it has no knowledge that we have an existing author in the database with ID 1 and name "Mosh Hamedani";
// there is two ways to resolve this, see these ways on the code below;
};
//context.Courses.Add(course);
//context.SaveChanges();
#endregion
// The first approach - WPF applications;
var authorsFirstApproach = context.Authors.ToList();
var author = context.Authors.Single(a => a.Id == 1);
var courseFirstApproach = new Course
{
Name = "New Course 2",
Description = "New Description",
FullPrice = 19.95f,
Level = 1,
Author = author
};
//context.Courses.Add(courseFirstApproach);
//context.SaveChanges();
// The second approach - this fits approach better in web applications; (can use in WPF too);
var courseSecondApproach = new Course
{
Name = "New Course 3",
Description = "New Description",
FullPrice = 19.95f,
Level = 1,
AuthorId = 1
};
context.Courses.Add(courseSecondApproach);
context.SaveChanges();
// There's also a third way to solve this problem, which is not very common:
// for example, if we have an object that is not in our context;
// *not recommended;
//var author2 = new Author() { Id = 1, Name = "Mosh Hamedani" };
//context.Authors.Attach(author2);
//var courseThirdApproach = new Course
//{
// Name = "New Course 4",
// Description = "New Description",
// FullPrice = 19.95f,
// Level = 1,
// Author = author2
//};
//context.Courses.Add(courseThirdApproach);
//context.SaveChanges();
// -----------------------
// Associating Objects
// Using an existing object in context;
//course.Author = context.Authors.Single(a => a.Id == 1);
// Using foreign key properties;
//course.AuthorId = 1;
}
private static void Main()
{
PlutoContext context = new PlutoContext();
// LINQ Syntax
var query =
from c in context.Courses
where c.Author.Id == 1
orderby c.Level descending, c.Name
select c;
// Projection
var query0 =
from c in context.Courses
where c.Author.Id == 1
orderby c.Level descending, c.Name
select new { c.Name, Author = c.Author.Name };
foreach (var course in query0)
{
Console.WriteLine(course.Name);
}
// Grouping
var query1 =
from c in context.Courses
group c by c.Level into g
select g;
foreach (var group in query1)
{
Console.WriteLine(group.Key);
foreach (var course in group)
{
Console.WriteLine("\t{0}", course.Name);
}
}
foreach (var group in query1)
{
Console.WriteLine("{0} ({1})", group.Key, group.Count());
}
// Joining - Inner Join
var query2 =
from c in context.Courses
join a in context.Authors on c.AuthorId equals a.Id
select new { c.Name };
// Joining - Group Join
var query3 =
from a in context.Authors
join c in context.Courses on a.Id equals c.AuthorId into g
select new { AuthorName = a.Name, Courses = g.Count() };
foreach (var x in query3)
{
Console.WriteLine("{0} ({1})", x.AuthorName, x.Courses);
}
// Joining - Cross Join
var query4 =
from a in context.Authors
from c in context.Courses
select new { AuthorName = a.Name, CourseName = c.Name };
foreach (var x in query4)
{
Console.WriteLine("{0} - {1}", x.AuthorName, x.CourseName);
}
// LINQ Extension methods
// Restrication
context.Courses.Where(c => c.Level == 1);
// Oredering
context.Courses.Where(c => c.Level == 1)
.OrderBy(c => c.Name)
.ThenBy(c => c.Level);
context.Courses.Where(c => c.Level == 1)
.OrderByDescending(c => c.Name)
.ThenByDescending(c => c.Level);
//Projection
context.Courses.Where(c => c.Level == 1)
.OrderByDescending(c => c.Name)
.ThenByDescending(c => c.Level)
.Select(c => new { CourseName = c.Name, AuthorName = c.Author.Name });
var tags = context.Courses.Where(c => c.Level == 1)
.OrderByDescending(c => c.Name)
.ThenByDescending(c => c.Level)
.SelectMany(c => c.Tags);
foreach (var t in tags)
{
Console.WriteLine(t.Name);
}
// Set Operators
context.Courses.Where(c => c.Level == 1)
.OrderByDescending(c => c.Name)
.ThenByDescending(c => c.Level)
.SelectMany(c => c.Tags)
.Distinct();
// Grouping
var groups = context.Courses.GroupBy(c => c.Level);
foreach (var group in groups)
{
Console.WriteLine("Key: " + group.Key);
foreach (var course in group)
{
Console.WriteLine("\t" + course.Name);
}
}
// Joining
// Inner Join - use when there is no relationship between objects
// but you need to join them
context.Courses.Join(
context.Authors,
c => c.AuthorId,
a => a.Id,
(course, author) => new
{
CourseName = course.Name,
AuthorName = author.Name
});
// Group Join - use for left join in sql between two tables and then use aggregate functions like count , or group by
context.Authors.GroupJoin(
context.Courses,
a => a.Id,
c => c.AuthorId,
(author, courses) => new
{
Author = author,
Courses = courses
});
// Cross Join - return every combination of two lists
context.Authors.
SelectMany(
a => context.Courses,
(author, course) => new
{
AuthorName = author.Name,
CourseName = course.Name
}
);
// Partitioning - return a page of records, ex : return 10 courses per page
context.Courses.Skip(10).Take(10); // skip first ten and get next 10 only
// Element Operators - return a single or first object
context.Courses.First();
context.Courses.OrderBy(c => c.Level).First();
context.Courses.OrderBy(c => c.Level).FirstOrDefault();
context.Courses.OrderBy(c => c.Level).FirstOrDefault(c => c.FullPrice > 100);
context.Courses.Single(c => c.Id == 1); // will through exception if ID 1 not found
context.Courses.SingleOrDefault(c => c.Id == 1); // will through exception if condition return many records
// Quantifying
context.Courses.All(c => c.FullPrice > 10); // returns true if all courses FullPrice is greater than 10
context.Courses.Any(c => c.Level == 1); // return true if we have at lease one course level equals 1
// Aggregating
context.Courses.Count(); // return courses count
context.Courses.Count(c => c.Level == 1); // return courses count of level one
context.Courses.Max(c => c.FullPrice); // returns max price
context.Courses.Min(c => c.FullPrice); // return min price
context.Courses.Average(c => c.FullPrice); // return average price
// IQueryable vs IEnumerable
IQueryable <Course> courses1 = context.Courses;
var filtered = courses1.Where(c => c.Level == 1); // filter will be part of our query to database
foreach (var course in courses1)
{
Console.WriteLine(course.Name);
}
IEnumerable <Course> courses2 = context.Courses;
var filtered1 = courses1.Where(c => c.Level == 1); // filter will not be included in query to database, filter will applied to results in memory
// Lazy Loading
var course0 = context.Courses.Single(c => c.Id == 2); // will load course without it's tags
foreach (var tag in course0.Tags) // tags will be fetched from database here
{
Console.WriteLine(tag.Name);
}
//// n + 1 - problem
//var coursesLazy = context.Courses.ToList(); // courses will be fetched here
//foreach (var course in coursesLazy)
// Console.WriteLine("{0} by {1}", course.Name, course.Author.Name); // for each Author a query to the database will be made to fetch author
//// Eager Loading all courses and thier author's
//var coursesEager = context.Courses.Include(c => c.Author).ToList(); // Courses and thier authors are loaded here
//foreach (var course in coursesEager)
// Console.WriteLine("{0} by {1}", course.Name, course.Author.Name);
//// Explicit Loading
//var authorExplicit = context.Authors.Single(a => a.Id == 1);
//// MSDN
//context.Entry(authorExplicit).Collection(a => a.Courses).Load();
//// Better way
//context.Courses.Where(c => c.AuthorId == authorExplicit.Id).Load();
//context.Courses.Where(c => c.AuthorId == authorExplicit.Id && c.FullPrice == 0).Load(); // loaded free courses only
//// Load free courses for all authors
//var authors = context.Courses.ToList();
//var authorIds = authors.Select(a => a.Id);
//context.Courses.Where(c => authorIds.Contains(c.AuthorId) && c.FullPrice == 0).Load();
// Adding new objects
var courseToAdd = new Course
{
Name = "New Course",
Description = "New Desciption",
FullPrice = 19.95f,
Level = 1,
AuthorId = 1
};
context.Courses.Add(courseToAdd);
context.SaveChanges();
// When we have object outside of our context
var authorFromOutside = new Author {
Id = 1, Name = "Qassim Alshakhoori"
};
context.Authors.Attach(authorFromOutside);
courseToAdd = new Course
{
Name = "New Course",
Description = "New Desciption",
FullPrice = 19.95f,
Level = 1,
Author = authorFromOutside
};
context.Courses.Add(courseToAdd);
context.SaveChanges();
// Updating existing objects
var courseToUpdate = context.Courses.Find(4); // Single(c => c.Id ==4)
courseToUpdate.Name = "C# MOICT";
courseToUpdate.AuthorId = 2;
context.SaveChanges();
// Removing objects
// With Cascade delete enabled
var courseToDelete = context.Courses.Find(6);
context.Courses.Remove(courseToDelete);
context.SaveChanges();
// With Cascade delete disabled
var authorToDelete = context.Authors.Include(a => a.Courses).Single(a => a.Id == 2);
context.Courses.RemoveRange(authorToDelete.Courses);
context.Authors.Remove(authorToDelete);
context.SaveChanges();
// Repository pattern
using (var unitOfWork = new UnitOfWork(new PlutoContext()))
{
var course = unitOfWork.Courses.Get(1);
var courses = unitOfWork.Courses.GetCoursesWithAuthors(1, 4);
var author = unitOfWork.Auhtors.GetAuthorWithCourses(1);
unitOfWork.Courses.RemoveRange(author.Courses);
unitOfWork.Auhtors.Remove(author);
unitOfWork.Complete();
}
context.Dispose();
}
