Lesson 60 - Creating an Entity Data Model

Tutorial Series: Free C# Fundamentals via ASP.NET Web Apps

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In the previous lesson, we created an SQL database running on a local server. What we want to do now is use an API within the .NET Framework, called the Entity Framework, to access/update that data via C# code. The Entity Framework is a subset of the entire ADO.NET API. It’s a newer aspect of the larger ADO.NET API that has a lot of the momentum when it comes to handling databases, but is certainly not the only way to access data in an SQL Server database. What the Entity Framework does is it serves up what's called an “Object-Relational Mapper.” Simply stated a mapper takes the data from the database and maps it to native C# structured classes and properties – making it easier to work with in code.

Step 1: Add an Entity Model to the LocalDbExample

This lesson is based on what we created in the previous lesson, so go ahead and start the project from where we left off. First, right-click on the project name “LocalDbExample” in the Solution Explorer and from the menu select:

Add > New Item


From here, go to the Data templates and select ADO.NET Entity Data Model, calling it “ACMEEntities”:


Next, select the option to model an “EF Designer from database,” since we started with a database and want to create an Entity model from it, rather than first create a model that can then applied to a database:


Then click “Next” on the following screen to simply create a “connection string” to the database you want to have the Entity model based upon. A connection string is held in a file that contains connection details required for an API, like the Entity Framework, to know where and how to go to connect to a database:


And in the following screen, checkmark the database table that you want to include in your Entity model. Since we only have one table – Customers – select that one:


By creating an Entity Data Model, we essentially create a series of entities that represent the data in the actual database, separate from the database itself. This creates a layer of abstraction from the underlying data that deals with all the details of creating, reading, updating and deleting data in the database.

Step 2: Understanding the Visual Entity Model and EDMX file

After that, you may get a warning whether or not you want to run this and click “OK” to confirm that. You will then be shown a visual model for the table and its data elements. If you had a variety of tables, they would all be represented here, and may even show connections between them wherever there is a relationship between the tables:


This visual model is available via the “ACMEEntities.edmx” file in the Solution Explorer:


The “.tt” files are generated as template files that will themselves generate a series of classes.


In this case, it'll create a Context class, which acts as a connection to the database. When we ask the database for something, the code that's generated here in this class will house the logic necessary to go out and connect to the database, and perform the actions that we've requested:


Step 3: Entity Generated Class Counterparts For Table Data

Meanwhile, the Customer.cs class was also generated, taking the various data points in the Customer table and converting them into suitable properties. The Entity Framework understands how to convert between.NET data types (string, GUID, and so on), and SQL Server data types (varchar, uniqueidentifier, and so on):


Step 4: Create a Server Control in Default.aspx Source View

Now create a simple resultLabel, except this time let’s create it directly within the Default.aspx code. We'll create an ASP Label control, give it an ID of resultLabel and runat the server:


The details of that that all means aren't in the scope of this lesson to discuss. Notice, however, that this yields the same result as we would get through creating it in Design view:


Step 5: Accessing the Entity Model in Code

Now in the Page_Load() of Default.aspx.cs, lets establish a connection to the database via code. We do this in the same way as we would create a new instance of a class:


This code will tell the Entity Framework that we're interested in getting all of the customer records from the customer table in our database. This querying of the database, retrieving the customer data and storing it in a local variable – customers – happens when this method executes. The last step in this method then iterates through the Name property in each Customer and prints it to the resultLabel:


When you run the application, you should see the result displaying the name data for our lone entry in the Database:


Related Articles in this Tutorial:

Lesson 1 - Series Introduction

Lesson 2 - Installing Visual Studio 2015

Lesson 3 - Building Your First Web App

Lesson 4 - Understanding What You Just Did

Lesson 5 - Working with Projects in Visual Studio

Lesson 6 - Simple Web Page Formatting in Visual Studio

Challenge 1

Solution 1

Lesson 7 - Variables and Data Types

Lesson 8 - Data Type Conversion

Lesson 9 - Arithmetic Operators

Lesson 10 - C# Syntax Basics

Challenge 2 - ChallengeSimpleCalculator

Solution - ChallengeSimpleCalculator

Lesson 11 - Conditional If Statements

Lesson 12 - The Conditional Ternary Operator

Challenge 3 - ChallengeConditionalRadioButton

Solution - Challenge Conditional RadioButton

Lesson 13 - Comparison and Logical Operators

Lesson 13 Challenge - First Papa Bob's Website

Solution - Challenge First Papa Bob's Website

Lesson 14 - Working with Dates and Times

Lesson 15 - Working With Spans of Time

Lesson 16 - Working with the Calendar Server Control

Challenge 4 - Challenge Days Between Dates

Solution - Challenge Days Between Dates

Lesson 17 - Page_Load and Page.IsPostBack

Lesson 18 - Setting a Break Point and Debugging

Lesson 19 - Formatting Strings

Challenge 5 - Challenge Epic Spies Assignment

Solution - Challenge Epic Spies Assignment

Lesson 20 - Maintaining State with ViewState

Lesson 21 - Storing Values in Arrays

Lesson 22 - Understanding Multidimensional Arrays

Lesson 23 - Changing the Length of an Array

Challenge 6 - Challenge Epic Spies Asset Tracker

Solution - Challenge Epic Spies Asset Tracker

Lesson 24 - Understanding Variable Scope

Lesson 25 - Code Blocks and Nested If Statements

Lesson 26 - Looping with the For Iteration Statement

Challenge 7 - Challenge For Xmen Battle Count

Solution - Challenge For Xmen Battle Count

Lesson 27 - Looping with the while() & do...while() Iteration Statements

Lesson 28 - Creating and Calling Simple Helper Methods

Lesson 29 - Creating Methods with Input Parameters

Lesson 30 - Returning Values from Methods

Lesson 31 - Creating Overloaded Methods

Lesson 32 - Creating Optional Parameters

Lesson 33 - Creating Names Parameters

Lesson 34 - Creating Methods with Output Parameters

Challenge 8 - Challenge Postal Calculator Helper Methods

Solution - Challenge Postal Calculator Helper Methods

Mega Challenge Casino

Solution - Mega Challenge Casino

Lesson 35 - Manipulating Strings

Challenge 9 - Phun With Strings

Solution - Challenge Phun With Strings

Lesson 36 - Introduction to Classes and Objects

Challenge - Hero Monster Classes Part 1

Solution - Hero Monster Classes Part 1

Challenge - Hero Monster Classes Part 2

Solution - Challenge Hero Monster Classes Part 2

Lesson 37 - Creating Class Files Creating Cohesive Classes and Code Navigation

Lesson 38 - Understanding Object References and Object Lifetime

Lesson 39 - Understanding the .NET Framework and Compilation

Lesson 40 - Namespaces and Using Directives

Lesson 41 - Creating Class Libraries and Adding References to Assemblies

Lesson 42 - Accessibility Modifiers, Fields and Properties

Lesson 43 - Creating Constructor Methods

Lesson 44 - Naming Conventions for Identifiers

Lesson 45 - Static vs Instance Members

Challenge 10 - Challenge Simple Darts

Solution - Challenge Simple Darts

Lesson 46 - Working with the List Collection

Lesson 47 - Object Initializers

Lesson 48 - Collection Initializers

Lesson 49 - Working with the Dictionary Collection

Lesson 50 - Looping with the foreach Iteration Statement

Lesson 51 - Implicitly-Typed Variables with the var Keyword

Challenge 11 - Challenge Student Courses

Solution - Challenge Student Courses

Mega Challenge War

Solution - Mega Challenge War

Lesson 52 - Creating GUIDs

Lesson 53 - Working with Enumerations

Lesson 54 - Understanding the switch() Statement

Lesson 55 - First Pass at the Separation of Concerns Principle

Lesson 56 - Understanding Exception Handling

Lesson 57 - Understanding Global Exception Handling

Lesson 58 - Understanding Custom Exceptions

Lesson 59 - Creating a Database in Visual Studio

Lesson 60 - Creating an Entity Data Model

Lesson 61 - Displaying the DbSet Result in an ASP.NET GridView

Lesson 62 - Implementing a Button Command in a GridView

Lesson 63 - Using a Tools-Centric Approach to Building a Database Application

Lesson 64 - Using a Maintenance-Driven Approach to Building a Database Application

Lesson 65 - Creating a New Instance of an Entity and Persisting it to the Database

Lesson 66 - Package Management with NuGet

Lesson 67 - NuGet No-Commit Workflow

Lesson 68 - Introduction the Twitter Bootstrap CSS Framework

Lesson 69 - Mapping Enum Types to Entity Properties in the Framework Designer

Lesson 70 - Deploying the App to Microsoft Azure Web Services Web Apps

Papa Bob's Mega Challenge

Papa Bob's Mega Solution Part 1 - Setting up the Solution

Papa Bob's Mega Solution Part 2 - Adding an Order to the Database

Papa Bob's Mega Solution Part 3 - Passing an Order from the Presentation Layer

Papa Bob's Mega Solution Part 4 - Creating the Order Form

Papa Bob's Mega Solution Part 5 - Adding Enums

Papa Bob's Mega Solution Part 6 - Creating an Order with Validation

Papa Bob's Mega Solution Part 7 - Calculating the Order Price

Papa Bob's Mega Solution Part 8 - Displaying the Price to the User

Papa Bob's Mega Solution Part 9 - Creating the Order Management Page


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