Model First Approach in Entity Framework
Read my previous two posts ‘Code First Approach in Entity Framework’ & ‘Database First Approach in Entity Framework’ for EF basics. In this post I’m directly going to jump on Model First Demo Project.
Demo MVC Application
Create a new ASP.NET MVC Project by New > Project > ASP.NET MVC 4 Web Application > ‘Internet Application’ Template because this template contains required js/css bundles and account setup. Even choosing ‘Internet Application’ as a template adds all required binaries for EF developments including ‘System.Data.Entity’.
Follow the steps for further demo.
Step 1: Adding ‘ADO.NET Entity Data Model’ File
For this, right click on Models > Add > New Item and in the Data section select ‘ADO.NET Entity Data Model’ and click on Add button. It will bring an ‘Entity Data Model Wizard’, in this window select ‘Empty model’, because we are going to create ‘Model First’ demo and click on finish button. You will get a ‘Model1.edmx[Diagram1]’ file this is also known as ‘Entity Data Model Designer’ and here we will design our database tables and also create the relationships.
Step 2: Adding Entity
To add Entity, right click on ‘Entity Data Model Designer’ surface and chose Add New > Entity and it appeared windows type Entity name as ‘Student’ and click on ok.
Step 3: Adding Properties for ‘Student’
Now, you got ‘Student’ mode, let’s add properties for this. There is two different ways to add properties.
Right click on ‘Student’ mode and navigate to Add New > Scalar Property.
Select ‘Id’ in ‘Student’ mode and press enter key on keyboard, this will bring a new property asking to enter name.
Step 4: Adding Relationships
Now, create following structure (two entities) by repeating step 2 and 3.
Now, we got two different entities on the ‘Entity Data Model Designer’ surface. Here we need a relationship between both entities like for each Student in ‘Student’ entity there will be many marks in ‘Mark’ entity. Means the concept is, we don’t want/accept any mark in ‘Mark’ entity which has no relation to ‘Student’ entity.
Now, for such structure we need to create relationship by adding ‘Association’. Right click on designer surface and select Add New > Association.
Now, you will get following window asking to arrange the relationship.
Don’t make any changes, because VS done everything we want smartly. We just need to understand options. As I said above, for every Student there will be many marks in Mark entity. We also got an Association Name (it is just a name of this relationship) and Navigation Property, let’s talk about this in depth.
Navigation properties in the Entity Framework provide a way to navigate an association between two entity types. A navigation property is defined by the NavigationProperty Element (CSDL) in the conceptual model. Every object can have a navigation property for every relationship in which it participates. Navigation properties allow you to navigate and manage relationships in both directions, returning either an EntityReference, if the multiplicity is either one or zero-or-one, or an EntityCollection, if the multiplicity is many. You may also choose to have one-way navigation, in which case you can delete the navigation property.
In simple word, navigation property just shows that there is some relation it maybe one to many, many to many, zero or one and displays the graphical line between both entities.
Foreign Key Property
You will also notice a checkbox in above image. The main characteristic of Foreign key association is a foreign key property exposed on a dependent entity. The foreign key property must be always exposed when you wish not to accept any entry who’s ‘StudentId’ is not available in ‘Student’ entity.
Note: If you try to delete ‘Student’ table before deleting ‘Mark’ table, you will get error message showing there is some dependencies.
Step 5: Configuring Model Properties
Just click on ‘Entity Data Model Designer’ surface and open the properties window.
In above image, you can modify the marked properties if you wish or keep it default.
Step 6: Generate Database from above model
Now, we have everything setup to create database from above structured model. For this, right click on ‘Entity Data Model Designer’ surface and select ‘Generate Database from Model’.
Now, in the appeared window, you can go with the default connection, I’m going to create a new connection.
And click on next button, it will generate a sql query and this query will be executed against above selected database. Now, click on finish to get sql file containing all sql information’s like how to created db, what will be the name of tables and what will be the relations etc.
You can handover the above query information to db end person to generate the database for your app. Let’s execute this query against above selected connection for now by right clicking on query file.
After executing the query file, you will notice a database with some tables that we have designed above.
Step 7: Adding Controller and Views
Let’s build the solution here Build > Build Solution, this will bring classes (in our case Model1.Designer.cs’) in Add Controller window.
Now, time to add controllers and views for both entities. Let’s begin by adding ‘Student’ controller.
Right click on Controller > Add > Controller and make following selection as given in image.
If you click on Add button above, will add required controller and its methods and also different views.
We need to add one more controller for ‘Mark’ entity, repeat above instructions and you will get following files.
Step 8: Running Application
Now run apps and try to insert record in ‘Mark’ without inserting any record in ‘Student’, you will be asked to select ‘Student’ here and still we don’t have any entry in ‘Student’. So, now we can see the impact of ‘Foreign Key’ here.
Let’s go back and make an entry in ‘Student’ and then in ‘Mark’ and you will get the list of Student here.
So, that’s all about the ‘Model First’ approach in Entity Framework. Thanks.