EF 4.2 Model & Database First Walkthrough

 

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The information in this post is out of date.

Visit msdn.com/data/ef for the latest information on current and past releases of EF.

For Model First see http://msdn.com/data/jj205424

For Database First see http://msdn.com/data/jj206878

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This post will provide an introduction to Model First and Database First development with the DbContext API, using the Entity Data Model Designer in Visual Studio.

You will need to have Visual Studio 2010 or Visual Studio 11 installed to complete this walkthrough.

 

1. Create the Application

To keep things simple we’re going to build up a basic console application that uses the DbContext to perform data access:

• Open Visual Studio
• File -> New -> Project…
• Select “Windows” from the left menu and “Console Application”
• Enter “ModelFirstSample” as the name
• Select “OK”

 

2. Create the Model

Let’s go ahead and add an Entity Data Model to our project;

• Project –> Add New Item…
• Select ‘Data’ from the left menu
• Select ‘ADO.NET Entity Data Model’ from the list of available items
• Name the model ‘PersonModel.edmx’
• Click ‘Add’

We are going to use Model First for this walkthrough but if you are mapping to an existing database you would now select ‘Generate from database’, follow the prompts and then skip to step 4.

• Select ‘Empty model’
• Click ‘Finish’

Let’s add a Person entity to our model:

• On the design surface; Right Click –> Add –> Entity
• Name the entity ‘Person’
• Click ‘OK’
• On the Person entity; Right Click –> Add –> Scalar Property
• Name the property ‘Full Name’

 

3. Create the Database

Now that we’ve defined the model we can generate a database schema to store our data:

• On the design surface; Right Click –> Generate Database from Model
• Click ‘New Connection…’
• Specify the details of the database you wish to create
• Click ‘OK’
• If prompted to create the database; click ‘Yes’
• Click ‘Next’ then ‘Finish’
• On the generated script; Right Click –> Execute SQL…
• Specify your database server and click ‘Connect’

 

4. Swap to DbContext Code Generation

The PersonModel is currently generating a derived ObjectContext and entity classes that derive from EntityObject, we want to make use of the simplified DbContext API.

To use DbContext we need to install the EntityFramework NuGet package:

• Project –> Add Library Package Reference…
• Select the “Online” tab
• Select the “EntityFramework” package
• Click “Install”

Now we can swap to using DbContext code generation templates:

• On the design surface; Right Click –> Add Code Generation Item…
• Select ‘Online Templates’ from the left menu
• Search for ‘DbContext’
• Select ‘EF 4.x DbContext Generator’ from the list
  (If you are using EF 5 you should select ‘EF 5.x DbContext Generator’ instead)
• Name the item ‘PersonModel.tt’
• Click ‘Add’

You’ll notice that two items are added to your project:

• PersonModel.tt
  This template generates very simple POCO classes for each entity in your model
• PersonModel.Context.tt
  This template generates a derived DbContext to use for querying and persisting data

 

5. Read & Write Data

It’s time to access some data, I’m padding out the Main method in Program.cs file as follows;

class Program 
{ 
  static void Main(string[] args) 
  { 
    using (var db = new PersonModelContainer()) 
    { 
      // Save some data 
      db.People.Add(new Person { FullName = "Bob" }); 
      db.People.Add(new Person { FullName = "Ted" }); 
      db.People.Add(new Person { FullName = "Jane" }); 
      db.SaveChanges(); 

      // Use LINQ to access data 
      var people = from p in db.People 
        orderby p.FullName 
        select p; 

      Console.WriteLine("All People:"); 
      foreach (var person in people) 
      { 
        Console.WriteLine("- {0}", person.FullName); 
      } 

      // Change someones name 
      db.People.First().FullName = "Janet"; 
      db.SaveChanges(); 
    }

    Console.WriteLine("Press any key to exit..."); 
    Console.ReadKey(); 
  } 
} 

 

Summary

In this walkthrough we looked at Model First and Database First development using the DbContext API. We looked at building a model, generating a database, swapping to DbContext code generation and then saving and querying data.

Rowan Miller

Program Manager

ADO.NET Entity Framework