In a recent blog post comment, someone asked “can you please tell them [EF Dev Team] some developers would like to use the Power Shell command script and not PM console to update database.”

If you look inside the package folder for Entity Framework 4.3 (or 4.3.1 or whatever is the current version in the future) there’s a tools directory and inside of there a migrate.exe command. It is the same as the update-database command with all of the same parameters.

Modified the original title of this post because it was derived from a misquote. Scott Hanselman clarifies with: The quote (what I said was) "EF is joining our team under ScottGu" and "EF is now the M in MVC". Scott Guthrie chimes in with “Yes – now part of my team (which includes ASPNET, WCF, WF, EF, Service Bus, BizTalk, Cache)”

_________________________________

Arthur Vickers, from the EF team, tweeted:

Also, very happy to be moving to @scottgu’s org with the rest of the Entity Framework team. Great for us, great for EF, great for Microsoft.

Just a reminder of Scott’s current role: “responsible for delivering the development platform for Windows Azure, as well as the .NET Framework and Visual Studio technologies used in building Web and server applications.”

A little later there was this on twitter from Noah Coad who is at Dallas Days of .NET (follow #dodn12 on twitter)

@shanselman at #dodn12 "just announced, we have an M in MVC, Entity Framework is now part of ASP.NET"

And then this interesting question from Daniel Bradley:

if Entity framework is to be part of ASP.NET, does this mean open-sourcing of the tools & framework?

Stay tuned….

(and since someone asked, EF has always been part of ADO.NET)

My newest course is live on Pluralsight.com. This one is about using the new data migrations feature of Entity Framework Code First. These were first introduced with EF 4.3. Migrations lets you update your database schema when your model changes rather than having code first completely drop and recreate the database. This lets you retain data and any other existing database objects that aren’t described in the model (e.g., triggers, functions, etc.)

Entity Framework Code First Migrations
(total 1 hr 09 m)

• Module 1: Introduction and Automatic Migrations
• Module 2: Code-Based Migrations

Here’s the entire list of EF courses I’ve done for Pluralsight (so far ). I’ve sorted them in the order you might want to watch them in.

Entity Framework (8 courses)

Entity Framework 4.0 By Example
Beginner
[02:18:50]
27 Aug 2010

Entity Framework and Data Models
Intermediate
[01:31:38]
5 Nov 2010

Designer Supported EDM Customization
Intermediate
[02:05:13]
6 Jan 2011

Querying the Entity Framework
Intermediate
[01:22:37]
28 Feb 2011

Entity Framework 4.1 – Code First
Intermediate
[01:58:17]
18 Jun 2011

Entity Framework 4.1 – DbContext Data Access
Intermediate
[01:21:19]
27 Sep 2011

Data Layer Validation with Entity Framework 4.1+
Intermediate
[01:53:49]
8 Feb 2012

Entity Framework Code First Migrations
Intermediate
[01:09]
6 Mar 2012

EF 4.3 added a new extension method for DbSet called AddOrUpdate.

It is meant for use with seeding data during migrations.

It looks like a nice method to add into your apps but that’s not it’s purpose.

The job of AddOrUpdate is to ensure that you don’t create duplicates when you seed data during development.

First, it will execute a query in your database looking for a record where whatever you supplied as a key (first parameter) matches the mapped column value (or values)  supplied in the AddOrUpdate. So this is a little loosey-goosey for matching but perfectly fine for seeding design time data.

More importantly, if a match is found then the update will update all and null out any that weren’t in your AddOrUpdate.

For example, if your type is:

Person

• Id
• Name
• UserName
• CreateDate
• Bio
• Email

And there is a row in the database with

5, GiantPuppy, Sampson, 1/1/2011, I drool, gp@notarealdomain.com

And your AddOrUpdate has

context.Aliases.AddOrUpdate(
           a => a.Name,
           new Alias { Name = "GiantPuppy", UserName = "Sampson", CreateDate = DateTime.Now},
           new Alias { Name = "JulieLerman", UserName = "Julie", CreateDate = DateTime.Now}
         );

The method will look for a row where whatever column maps to the Name property has the value GiantPuppy. It will then update all of the mapped properties.

• Name: GiantPuppy
• UserName: Sampson
• CreateDate: whatever the time is
• Bio: null  (because it wasn’t provided)
• Email: null (because it wasn’t provided)

This is about the same as doing an update in a disconnected app where you attach an object, mark it as modified and call SaveChanges. I see people do this in MVC apps all the time. If there are properties that were left null in the object because you didn’t care about them in this particular case, the database values will get overwritten with null. Except this is worse because it’s not leaning on your entity key (e.g. Id mapped to primary key).

So be careful out there. Me? I’m planning to use AddOrUpdate only for seeding migrations!

Update: I thought it would be useful to answer Livingston’s question here in the main post.

The update will update all of the properties it sees as changed.

It queries for the match (name==GiantPuppy), compares the values in the AddOrUpdate command to the results and updates anything that’s different.

So the results of the query would return the Id field for Giantpuppy. The migration will see that GiantPuppy’s seed Bioi(null) is different than the database Bio (“I drool”), that the email (null) is different than the database email and that the createdate value is also different. 

Here is the update command it sends to the database:

exec sp_executesql N’update [dbo].[Aliases]
set  [Email] = null, [Bio] = null, [CreateDate] = @0
where ([Id] = @1)
from [dbo].[Aliases]
where @@ROWCOUNT > 0 and [Id] = @1′,
N’@0 datetime2(7),@1 int’,@0=’2012-02-29 20:57:23.2779868′,@1=3

It’s updating everything that’s different…. email, bio and CreateDate.