ORM in C#Using Visual Paradigm

By : Imal Hasaranga Perera

What is ORM? Introduction to VP Using VP to Generate RDB Generating C# .NET Persistent Library Demo of how to use Persistent library Q & A

Agenda

What is ORM ???

Object Relational Mapping, A way of getting object-oriented languages and relational databases to work together Relational

world

Stu

User

B..A…

Object world

Mapping

'Object-Relational Impedance Mismatch' is just

a fancy way of saying that object models and

relational models do not work very well together.

RDBMSs represent data in a tabular format ,

whereas object-oriented languages, such as Java,

C# represent it as an interconnected graph of

objects. Loading and storing graphs of objects

using a tabular relational database exposes us to 5

mismatch problems

The Object-Relational Impedance Mismatch

1) Granularity

2) Inheritance

3) Identity

4) Associations

5) Data Types

The Object-Relational Impedance Mismatch

1. Granularity

Sometimes you will have an object model which has more classes than the number of corresponding tables in the database

public class Teacher{

}

public class School{

}

2. Inheritance

Inheritance is a natural paradigm in object-oriented programming languages. However, RDBMSs do not define anything similar to Inheritance

User_main

Student Teacher

Inheritance

3. Identity

A RDBMS defines exactly one notion of 'sameness'

Teacher_id = 2233

Thread 1

Thread 2

Teacher

Teacher

4. Associations

Associations are represented as unidirectional references in Object Oriented languages whereas RDBMSs use the notion of foreign keys. If you need bidirectional relationships in C#, you must define the association twiceClass user_main {

Teacher teacher;

}

Class Teacher {

}

5. Data Types

When we consider about data types there a mismatches, simply String might have limited size than a varchar data type

String Varchar(150)

Mismatches Between Date and time in the object world and the relational world

Reason for using ORM??

Speeds-up Development - eliminates the need for repetitive SQL code.

Reduces Development Time. Reduces Development Costs. Overcomes vendor specific SQL differences - the

ORM knows how to write vendor specific SQL so you don't have to.

Rich query capability. ORM tools provide an object oriented query language.

User nuser = UserFactory.createUser();

nuser.Fname = t1.Text;nuser.Lname = t2.Text;nuser.Type = t3.Text;nuser.Save();

t.commit();

Lets Get Started With Visual Paradigm

Relational database

Example ER Diagram Created by Using VP

Code Generating Process in VP

Generate C# project using Visual paradigm

Q & A

Thank You