Create Entity Framework Data Context for LINQPad 4

In what I hope to be my last prerequisite post for Entity Framework on LINQPad, I will create a Data Context for my Entity Model Assembly.

I like to use LINQPad as a snippet editor because of its cool Dump() extension method. This platform makes it easy to play What If with a new technology.

For the purpose of these steps, I’m going to pretend you are using the assembly we created in [last post]. So here are the steps:

1. Open LINQPad 4
2. Click on Add Connection
3. In the Choose Data Context window, choose Entity Framework.
   
4. In the LINQPad Connection window, Browse for your EF Model Assembly
5. In the Choose Custom Type:
   
   • In Custom Type Name you should see PubsModel.pubsEntities
   • In Entity Data Model, choose From Same Assembly, PubsModel should be in the list below
   • Click OK
   
6. Accept the remaining defaults by clicking OK.

Building an EF 4 Model Assembly for Pubs DB

For this EF building block, I am going to build a Model Assembly. This assembly will contain the Model for the famous Pubs database. You can download Pubs along with Northwind from Microsoft.

I like the idea of separating my model for the rest of my app. I will use this model to LINQPad (and perhaps WinForms, WPF, etc.). I can link it directly to my UI or through a labyrinth of assemblies that I put between my UI (if I even have one).

Since you don’t have to write any actual code, the steps below should work for both C# and VB. They were tested on both Express Editions.

So here we go:

1. Create a new Project, call it PubsModel
   I like to use the pattern [SomeName]Model, where SomeName may be the name of the application or database.
2. Delete Class1.cs or Class1.vb
   Microsoft want to be helpful, I’ve probably destroyed a thousand Class1s
3. Project => Add New Item. (Alt+Shift+A)
4. Select ADO.NET Entity Data Model
5. Name it PubsModel.edmx
6. In the Entity Data Model Wizard, select Generate from database
7. In the next window, select pubs.mdf. If pubs.mdf is not on the list, you will need to click New Connection to add it to the list.
   Since this is Visual Studio Express, I am only allowed to make a Microsoft SQL Server Database File connection.
8. Set the value for Save entity connection settings in App.Config as: to pubsEntities.
9. Visual Studio asks you if you want to make a local copy of the database file.
   I usually answer “No” so I can play with the data with Microsoft SQL Server Management Studio. Of course any change I make to the data will affect the “Master” database.
10. Select Tables, Views and Stored Procedures.
11. Keep the defaults for Plurlaize or singularize generated object names and Include foreign key columns in the model.
12. Set Model Namespace to pubsModel
13. Click Finish.

After some churning and reformatting, you will get a model that looks like this

.

Starting LINQPad 4 from Visual Studio Express

As I am writing this year’s Code Camp presentation about Entity Framework, I’ve come across a problem: I want to use Visual Studio Express 2010 AND I want to demonstrate Linq to Entities using LINQPad 4. If I were using a commercial version of Visual Studio, I could use Start Action = Start external program. I can’t just launch LINQPad and edit my project because LINQPad would lock my assembly and Visual Studio would refuse to build a new one.

So, to work around this limitation, I added a console project that would launch LINQPad and wait for it to return.

C#:

using System.Diagnostics;
namespace LaunchLinqPad
{
    class Program
    {
        private const string LINQPAD_EXE = 
            @"C:\Program Files (x86)\LINQPad4\LINQPad.exe";
        static void Main(string[] args)
        {
            var process = new Process();
            process.StartInfo = new ProcessStartInfo(LINQPAD_EXE);>
            process.Start();
            // Without this, the program will exit immediately
            process.WaitForExit();
        }
    }
}

VB:

Module Module1
    Const LINQPAD_EXE = "C:\Program Files (x86)\LINQPad4\LINQPad.exe"
    Sub Main()
        Dim process As New Process()
        process.StartInfo = New ProcessStartInfo(LINQPAD_EXE)
        process.Start()
        ' Without this, the program will exit immediately
        process.WaitForExit()
    End Sub
End Module

A couple of issues:

• This doesn’t work with LINQPad 4 (and newer)
• I can’t step into my code.

Even with these limitations, I find this helpful because doing this endures that LINQPad is closed before I recompile, therefore preventing me from locking up the file that I am building.

Happy Groundhog Day!

Punxsutawney Phil, some rodent 2,000 miles from me sees his shadow so we get 6 more weeks of winter. Had he not seen it, winter would only 42 days left. I will have my traditional Groundhog Day dinner of pork sausage.