Entity framework is a new concept which allows developers to code against a conceptual model (which we create ourselves) rather than coding directly against a relational schema (database). This means that developers can take a slice out of the database cake and eat it rather than having to worry about eating the whole cake as a single piece. To taste this cake, its best to create a simple application that uses entity framework to connect with a database. The following guide will help you do exactly that.
Create a new application (in this example I will be using an MVC3 application) and name it DatabaseProject. Go to the solution explorer and do the following:
· right click “Models”,
· “Add ›”,
· “New item”,
· click “data” in the left hand tab then select “ADO.Net entity data model” and click “Add” (this will open a wizard)
· In the wizard, click “Generate from database” and click next.
You can create a new database connection by clicking on “New connection”. It will start another wizard which will ask you for database related information (which sometimes includes the IP address of server hosting the database) and username/password. Once you have entered this information, click “Ok”.
You will now return to the original wizard where at the bottom you will have a ticked checkbox labelled “Save entity connection settings in web.config as:”. Under this label there will be a default name of “DecisionCentreEntities”. Change this is to NameofConnection for simplification.
After changing the name click “Next”.
This will retrieve the list of all tables in the database with a checkbox next to each table. Check/tick the tables that you want in your model (or the tables that will be accessed by your code). After this, click “Finish” to exit the wizard.
You can now see a diagram of selected tables on a white surface which should look like this (I only ticked one table but you can tick as many as you want). This is your data model:
· In this diagram right click on the white surface and click “Add code generation item”.
· Click “Code” in the left hand tab then select “ADO.NET Entity Object Generator” and click Add.
· Build the project.
Our data model is ready to use.
Go to the controller (or any other class) and run queries on the database tables using the data model you just created.
Add the following using statement on the top “using DatabaseProject.Models”.
In a simple example we will run a query (we will be using a Linq query as an example) which returns all rows from the table “customers”.
using(var db = new NameofConnection())
{
object obj = (from r in db. customers select r).ToList();
}
This code will perform the query “select * from customers” and return the result. The result will then be converted into a list which will be copied on to the object “obj”.
In another example we will run a query which will add a new row to the table “customers”.
using(var db = new NameofConnection())
{
db. customers.AddObject(row);
db.SaveChanges();
}
With this we have now successfully tasted the cake and can use similar codes to perform other functions with our database.
