ntroducing K-Pattern: A Rapid Way to Make CRUD Operations with Entity Framework

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Introduction

Earlier in the last year I made a different approach to work on Entity Framework and in that I made some classes to handle the ObjectContext in single request scope and some extension methods to handle Insert / Update / Delete for all the edmx designer classes. Using that way I realized that how fast we can make applications with it but there are some things which are missing on that way. I worked on those drawbacks and now it’s in front of you.

This article is a remake of my earlier Article/Tip "Best way to use Entity Framework". I’ll describe new features and methods of “Helper.cs” class and will also compare this approach with some other approaches in the market in this article.

Background

Please go through the Part 1 before reading this article to understand the “Global Context” and “Helper” classes. After writing the 1st part, Debates were done among the developers that are is this the “Best way to use Entity Framework”? So to make it more understand it is best because of below things:

• DataContext alive and disposes on HttpContext basis so you do not need to write the code for initialize and dispose again and again in code blocks.
• The Insert, Delete and Update methods are attached with Data Context Entity classes without any change effect in the original designer file. So developer does not need to write individual functions for these operations for each entity class.
• Single Method for Insert and Update.
• Easy and Fast to implement

However, there are some other patterns that also follow the same rule but there are lot of code involves to making it happen.

What's New?

The previous “Helper.cs” doesn’t allow Insert/Update/Delete operations on relational entities therefore It only works on Single Entity. This was the major drawback but now I have added some new methods to get overcome this issue. There is a new enum Operation introduce to define EntitySet Operations like Added, Modified and Deleted. New extension methods have been defined for three classes EntityObject, EntityCollection<T> and ObjectContext. The list of methods with their classes and signatures are mentioned below:

Class	Methods	Description
EntityObject	AttachMe(this EntityObject objEntity)	Attach the current entity object with defined Global Context in Global.cs.
	AttachMe(this EntityObject objEntity, Operation oper)	Attach the current entity object with defined Global Context in Global.cs and Change its state according to the provided Operation enum
	DetachMe(this EntityObject entity)	Detach the current entity object with defined Global Context in Global.cs
EntityCollection<T>	AttachUs<T>(this EntityCollection<T> entities, Operation oper) where T : EntityObject	Generic method to attach the whole collection with define Global Context in Global.cs
	DetachUs<T>(this EntityCollection<T> entities) where T : EntityObject	Generic method to attach the whole collection with define Global Context in Global.cs
ObjectContext	AttachObject(this ObjectContext context, EntityObject objEntity)	Attach the provided entity with provided context.
	AttachObject(this ObjectContext context, EntityObject objEntity, Operation oper)	Attach the provided entity with provided context and change its state according the provided operation.
	DetachObject(this ObjectContext Context, EntityObject entity)	Detach the provided entity with provided context.

Let's Get Started

To demonstrate the new methods, we are going to make a DB (db_EntityFrameworkSample) and create two tables which have One to Many Relationship between.

In above diagram there are two tables Course and Student and they are associated via One to Many Relationship. We are going to perform operations on these tables in following order.

Single Entity Operations

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Course objCourse = new Course
{
    Name = "B.Sc.",
    Duration = "3 Years"
};

objCourse.Save();

Insert Parent & Insert Children

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Course objCourse = new Course
{
    Name = "M.Sc.",
    Duration = "3 Years"
};

objCourse.AttachMe();   // Here we attached the current object with entity object context to perform operations on children entities

objCourse.Students.Add(new Student { Name = "John", FName = "David" });
objCourse.Students.Add(new Student { Name = "Bob", FName = "Jason" });

objCourse.Save();

Update Parent & Insert Children

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Course objCourse = Course.GetCourse(2);  // Get MCA Cource

objCourse.Students.Add(new Student { Name = "Niroo", FName = "Rob" });
objCourse.Students.Add(new Student { Name = "Chirs", FName = "William" });

objCourse.Save();

Update Parent & Update Children

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Course objCourse = Course.GetCourse(2);  // Get MCA Course

objCourse.Students.ElementAtOrDefault(0).BirthDate = new DateTime(1986, 12, 15);
objCourse.Students.ElementAtOrDefault(1).BirthDate = new DateTime(1990, 7, 15);

objCourse.Save();

Update Parent & Delete Children

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Course objCourse = Course.GetCourse(4);  // Get M-Tech Course

objCourse.Duration = "4 Years";
objCourse.Students.AttachUs(Operation.Delete); // Attach student with context and change the EntityState to Deleted

objCourse.Save();

Delete Parent & Delete Children

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Course objCourse = Course.GetCourse(3);  // Get B-Tech Course

objCourse.Students.AttachUs(Operation.Delete); // Attach student with context and change the EntityState to Deleted

objCourse.Delete();

Above are sample codes which define the data operations between Parent-Child entities with different combinations using "K-Pattern".

Comparision With Repository Pattern

Feature	K-Pattern	Repository Pattern
Easy to implement	YES	NO
Context Scope in Single Request	YES	YES (With IOC)
Suitable Project Types	Small and Medium Types	Large Type
Support for EF Approaches	Database First	Code First and Database First

Conclusion

This is all about the K-Pattern. Thre are lot of discussion coming along with this approach and I'll be waiting for your reviews and suggestions to improve it better. Please downaload the source code, create the DB with the available SQL Script, chagne the conenction string and run it straight.

Thanks for reading. Happy coding.

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)