Julia Lerman's Blog, page 21

.NET/Sharepoint Dev Job in Albany/Saratoga NY area

Hallam-ICS is looking for a developer for their Malta, NY office.

Requirements:

Strong OOD/OOP skills. Winforms, WPF, Silverlight and ASP.NET, mobile application development including MVC WCF Web services development Expert knowledge in the C# & VB.NET Programming languages (ObjectiveC is a plus) Strong background in designing relational databases, queries, stored procedures and functions. Experience with front end web development tools, including XHTML, CSS, JavaScript, AJAX, JQuery Experience with XML and XSLT Experience using third party user controls Designing and implementing development workflow in Sharepoint. Experience with Change management systems. Experience with SCADA systems or PLC's preferred but not necessary.

This individual will be designing a relational database backed web, desktop, mobile application to replace an antiquated system currently in use. There will be heavy emphasis on .NET, Microsoft SQL Server 2008, WCF and WinForms/Silverlight written in C#. This system may be integrated with various mobile platforms for tablet and phone. This individual will be responsible for all Microsoft Sharepoint design and implementation including generating workflows and management of document control. Experience with in-process change management systems highly desired.

Additionally, this individual may participate in QAQC document review of processes and procedures, SCADA development and PLC programming as required to support other team members when necessary.

Any interested candidates can send their resume to Keith Flaherty at kflaherty@hallam-ics.com.

Using T4Scaffolding to Create DbContext and Repository from Domain Classes

You may already be familiar with the fact that ASP.NET MVC 3 tooling includes a scaffolding option that let's you point to a domain class and automatically build a Controller, a set of Views and if it does not exist yet, an Entity Framework DbContext class expose that class. The controller CRUD code uses the DbContext to perform it's operations. Scott's Guthrie & Hanselman both introduced us to this in blog posts last spring and I've certainly demo'd it way too many times.

This is handy but it puts all of the data access code into the controller. In other words, the controller works directly with the DbContext to perform queries & updates (etc).

If you have been paying attention, you may also be aware of the MVCScaffolding NuGet package that adds to these capabilities.

With this installed there are two new templates added to the MVC Add Controller wizard, one which adds a simple repository to the mix.

MVCScaffolding relies on another NuGet package, T4Scaffolding which contains many of the scaffolding templates used by MVCScaffolding.

I was working on the back end of a new app that may or may not have MVC as it's front end UI. I had created my domain classes and the next step was to create a DbContext to wrap them as well as repositories. I didn't want to code those by hand. I wanted that MVC tooling to get some of the grunt work out of the way for me. A little reading helped me learn that I could use the T4Scaffolding directly to get the same DbContext & Repository creation without being part of an MVC app (i.e. no controllers or views created).

Here's how I worked it out.

In my solution where I already had my DomainClasses project, I added a new project, Data Layer.

I then installed Entity Framework via NuGet into this project:

Notice that NuGet automatically picks up the the latest version of EF, 4.3. I could have used the Package Manager Library UI to install EF, but since I had to the rest in the console window, I'm just doing all of these tasks in the console window.

Next, I install T4Scaffolding.

Important Pointers!

Currently, T4 Scaffolding will install EF 4.1 if you don't already have EF 4.1 or greater in your project. That's why I installed EF first, so I can be sure to use the newest version. In the package manager console window, I have my default project pointing to DataLayer. I often forget to specify the project and install NuGet packages into the wrong project.

With the package installed, I can now start working towards letting it build out the context & repository for me.

First I need to reference DomainClasses from the DataLayer project

Then I build the solution so that DataLayer can see the DomainClasses for the next step.

Now in the Package Manager Console Window, I'll use the command to build the repository code. The T4 template that builds the context & repo is called repository. The command is scaffold. I want to run scaffold using the repository template and base the output on my Alias class. I must use Alias' fully qualified name so that it can be found.

The command is

scaffold repository DomainClasses.Alias

.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
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.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }

However, I want to specify the name of my context. The default will be DataLayerContext (using the project name). I want it to be TwitterContext.

scaffold repository DomainClasses.Alias -DbContextType:TwitterContext

.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }

The result is that a new context & repository class get created in the target project (DataLayer).

There's some default behavior that is not exactly to my liking and I can use additional parameters as well as modify the T4 template (here's a post from Steve Sanderson as part of the MVC Scaffolding series that will help with that) but for now I'm happy to just move files around, which I'll do shortly.

Here's the context class.

public class TwitterContext : DbContext
{
public DbSet<DomainClasses.Alias> Aliases { get; set; }
}

.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }

Now I'll add another class from my domain model to the mix: Tweet.

Notice that since TwitterContext already existed, we don't get a second context class, the template alters the existing one:

public class TwitterContext : DbContext
{
public DbSet<DomainClasses.Alias> Aliases { get; set; }
public DbSet<DomainClasses.Tweet> Tweets { get; set; }
}

.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }

Finally, I'll just move things around so they are more to my liking:

I've created a Repositories project that has references to EF4.3, DataLayer and DomainClasses.

Now I can use the context & repos as they are or take the generated code (which has saved me a lot of time) and tweak it to my needs. But this has taken a lot of the repetitive typing away from me and started me on a path of success. Happiness.

Thanks to Steve Sanderson & others who worked on this tooling!

(Oh and if you could modify the template to pull in "latest version of EntityFramework.dll", that would be handy.)

New EF Validations Video on Pluralsight

My newest course is live on Pluralsight.com. This one is all about performing data layer validations in EF 4.1 (4.2, 4.3) using the Validation API that’s part of the DbContext.

Working with the DbContext Validation API

(total 1 hr 54 m)

Module 1: Data Layer Validation with Entity Framework DbContext
Module 2: Customizing Entity Framework Data Layer Validation
Module 3: Integrating Entity Framework Validation with MVC and WCF Data Services

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 (7 courses)

Beginner

[02:18:50]

27 Aug 2010

Intermediate

[01:31:38]

5 Nov 2010

Intermediate

[02:05:13]

6 Jan 2011

Intermediate

[01:22:37]

28 Feb 2011

Intermediate

[01:58:17]

18 Jun 2011

Intermediate

[01:21:19]

27 Sep 2011

Intermediate

[01:53:49]

8 Feb 2012

Coming soon: Entity Framework 4.3: Code First Migrations and other changes

What do you want to see in Entity Framework?

A friendly reminder about the UserVoice site where you can suggest and vote on features you'd like to see in Entity Framework (http://data.uservoice.com/forums/72025-ado-net-entity-framework-ef-feature-suggestions) or in WCF Data Services (http://data.uservoice.com).

The EF team is wrapping up work on changes to the core EF APIs that will be part of the .NET 4.5 release. We've had access to the preview of these new features since June 2011. Here's an MSDN Magazine article reviewing some of the most prominent features that you'll find in there: http://msdn.microsoft.com/en-us/magazine/hh394151.aspx.

But EF continues to evolve. The team pays close attention to the suggestions developers make (and vote on) on user voice. In fact, it's a bit of a popularity contest. If one feature suggestion has hundreds of votes, it will get a lot more attention from the team than a suggestion with only 10 votes.

Here's a look at hot suggestions.

Top 10 Suggestions Overall

Improved SQL Generation (status=Started) 1204 votes Batch CUD support (status=Under Review) 981 votes EF Support for Second Level Cache (status=Under Review) 535 votes Entity Designer: Speed up & Optimize for using with ~200+ entities 453 votes Support for multiple databases (status=Under Review) 441 votes Designer Support GUID as Entity Key  429 votes Schema Migration a la Rails Migrations (status =Started (Code First Migrations)) 406 votes TPT (Table-Per-Type) Inheritance Performance (coming in .NET 4.5) 369 votes Allow filtering for Include extension method (status=Under Review) 319 votes Allow default date = NOW and provider.MinDate in CSDL (my suggestion ) 216 votes
(this isn't as much of a problem now with code first, but for EDMX it's still an issue)

There are currently 276 overall. Some have been completed. Some may be duplicates. But if there are features you care about getting into EF, take a look at the list and vote and *promote* the ones you care about.

Vermont IT Jobs: SysAdmin at NRG Systems in Hinesburg (a cool company…c'mon do it!)

http://www.nrgsystems.com/
Hinesburg, Vermont Desktop/Systems Administrator Job Description

Key Focus

The Desktop/Systems Administrator is responsible for providing first line support to NRG's information technology users; assuring that user's IT resources are performing as required. This individual helps users achieve their goals by providing excellent customer service for IT issues/requests, while at the same time assuring the integrity and security of NRG's information resources.

The Desktop/Systems Administrator will report to the Information Technology Manager and will work with the information technology team to achieve the objectives of the department that are aligned with the company strategic goals.

Primary Responsibilities Manage NRG's IT Help Desk ticket system by monitoring ticket submission, resolving tickets that fall within the Desktop Administrator job responsibilities, and assigning other tickets to appropriate individuals within the IT department. Resolve user requests for problem resolution regarding desktop hardware, printers and other peripherals, e-mail, MS Office applications and other supported desktop applications, internet/intranet access, in a timely and professional manner. Coordinate the procurement, provisioning, and management of new desktop/laptop computers, printers, A/V equipment, and desktop application licenses to support current and new users. Assure that NRG's spam, virus, and malware protection is functioning at optimal level. Manage user accounts and provide IT orientation to new employees. Monitor server backup performance, assure proper backup tape storage and rotation, and identify issues that require resolution. Purchase and install new versions of desktop software to maintain currency. Utilize VMWare Virtual Center to support the Network Administrator in managing and maintaining the server and network environment. Qualifications 4-year degree in computer science, software engineering, or related field 3+ years IT experience with hardware and software support Exceptional communication and teamwork skills. Excellent analytical and problem resolution skills. Excellent organizational skills. Ability to work independently, and prioritize multiple tasks Demonstrated knowledge of desktop/laptop hardware repair for common issues such as hard drive replacement, memory replacement, etc Demonstrated knowledge of Windows XP, Windows 7, Windows Server, VMWare Virtual Center, SQL Server, Active Directory, IIS, Linux. Microsoft certifications a plus Experience in a manufacturing environment a plus

Oracle Releases Provider with EF 4 Support (but not really EF 4.1 and EF4.2)

Oracle has finally released it’s version of ODP.NET that supports Entity Framework for use in production environments.

This is great news for many developers! 

And they report that this release supports EF 4.1 and EF 4.2. That should mean Code First and DbContext but thanks to Frans Bouma sending me the limitations doc (that is part of the installation ) we can see that they aren’t! Too bad.

7. ODP.NET 11.2.0.3 does not support Code First nor the DbContext APIs.

So, that means “not really EF 4.1 and EF 4.2 support” in my opinion. But they told us already that Code First & DbContext weren't going to make it in. So it was just the momentary surprise of misunderstanding their meaning about EF4.1 & 4.2 support that deflated me a bit. ;)

Howver...I imagine Code First and DbContext are still leading edge for the types of big corporations that use Oracle. The core EF 4 support is a big deal.

I’ll follow up with Oracle for clarification.

More from Oracle (including downloads) here: http://www.oracle.com/technetwork/topics/dotnet/whatsnew/index.html

EMail Q&A: What about Entity SQL and why direct DB access?

I received this pair of questions about EF in email and thought I would share the questions and my reply.

Q:

I've read some articles about Code First, I've tried to do some samples and I'm going to read you last book.

I'm surprised about 2 issues. The first is that it's possible to write native SQL code (with context.Database.ExecuteSqlCommand and context.Database.SqlQuery methods) and the second is that I've not been able to use EntitySQL or Query Builder Methods.

Now, the idea of EF was create a model, operate with objects and use a common language (EntitSql) to interact with "some" databases. But now? We are coming back? Yes, we can use Linq2Entities and SaveChanges but I don't understand the philosophy of these opened doors upon the database.

I'm wrong?

What's your idea?

My A:

Dbcontext doesn't replace ObjectContext. It just makes it easier for devs to access the most common things.

You can still use ObjectContext. You can even use DbContext and access ObjectContext functions when you need to.

Entity SQL was created before the data team knew about LINQ. You can express most queries with LINQ and it works with any EF-compliant database provider, just as ESQL does.

The direct database access command features are a "backdoor" that devs asked for. It should be used only on rare occasions when you need to access something in the database that is not part of the model.

Our Code First Ebook 1/2 price today on O'Reilly site

From @OReillyMedia: Ebook Deal of the Day (Dec 9, 2011): Programming Entity Framework: Code First - $7.49 (Save 50%) http://oreil.ly/swjSwq

Use Projections and a Repository to Fake a Filtered Eager Load

Entity Framework's Include method which eager loads related data in a query does not allow sorting and filtering. People ask for this feature frequently.

There is a way around the problem,  I wrote about it in  the June Data Points column in MSDN Magazine (Loading Related Data: http://msdn.microsoft.com/en-us/magazine/hh205756.aspx) but since I just saw another comment on twitter about this, I thought I would stop working on Chapter 7 of the DbContext book that is already delayed and write a quick blog post about using a projection instead.

One caveat…you cannot do this if you have a long running context and you want the objects to remain attached to the context. If there are other related entities in the context, the context will always give them to you. More on this at the end of the post.

Okay, today's model will be based on a roads and trees on that road. I need some type of guide because we've been socked in with fog for two days and I can barely see the trees across my road.

We'll have two classes (and no I'm not trying to rub in the fact that we don't have geo support yet, but it's coming in .NET 4.5.)

public class Tree
{
public int Id { get; set; }
public string Description { get; set; }
public decimal Lat { get; set; }
public decimal Long { get; set; }
public int RoadId { get; set; }
}
public class Road
{
public Road()
{
Trees = new List<Tree>();
}
public int Id { get; set; }
public string Name { get; set; }
public string Town { get; set; }
public List<Tree> Trees { get; set; }
}

.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }The way loading works in Entity Framework is an all or nothing scenario with one exception.

The DbContext lets you do a filter in an explicit load (i.e. after the root is already in memory). Here's a passing test which loads only maple trees and checks to see that the count of non-maple trees is NOT greater than 0.

(MyInitializer seeds the database with one road that has three related Trees (a maple, a maple and a pine)).

[TestMethod()]
public void CanFilterOnExplicitLoad()
{
Database.SetInitializer(new MyInitializer());
var context = new DataAccess();
var road = context.Roads.FirstOrDefault();
context.Entry(road).Collection(r => r.Trees)
.Query().Where(t => t.Description.Contains("Maple"))
.Load();
Assert.IsFalse(context.Trees.Local
.Where(t=>!t.Description.Contains("Maple"))
.Count()>0);

}

But that's beside the point, since the question is about eager loading.

You can't filter when eager loading with Include.

But you can get the results you want eagerly if you project.

[TestMethod()]
public void CanFilterOnProjection()
{
Database.SetInitializer(new MyInitializer());
var context = new DataAccess();
var road = context.Roads
.Select(r=>new{
r,
r.Trees.Where(t=>t.Description.Contains("Maple")})
.FirstOrDefault();
Assert.IsFalse(context.Trees.Local
.Where(t => !t.Description.Contains("Maple"))
.Count() > 0);
}
}


.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }

That's nice but whine whine whine, I returned an anonymous type.

If you use a repository, you can hide that.

public class DumbRepositoryButGoodEnoughForThisDemo
{
DataAccess _context=new DataAccess();

public List<Road> GetRoadsWithFilteredTrees(string treeFilter)
{
var roadAndTrees = _context.Roads
.Select(r=>new{
Road=r,
Trees=r.Trees.Where(t=>t.Description.Contains("Maple"))})
.ToList();
return roadAndTrees.Select(rAt=>rAt.Road).ToList();
}
}


.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }

When I return the list of roads from the projection, the Trees will be attached thanks to the context recognizing the relationships.

Here's another test that does pass:

[TestMethod()]
public void RepositoryFilteredRoadsReturnsRoadWithTrees()
{
Database.SetInitializer(new MyInitializer());
var rep = new DumbRepositoryButGoodEnoughForThisDemo();
var roads = rep.GetRoadsWithFilteredTrees("Maple");
Assert.IsTrue(roads.FirstOrDefault().Trees.Any());
Assert.IsFalse(roads.FirstOrDefault()
.Trees
.Where(t => !t.Description.Contains("Maple"))
.Count() > 0);

}


.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }

And a screenshot as further proof:

 

Scenario When This May Not Work As Expected

As Brian points out in the comments, there is one BIG draw back that is also a problem with the filtered explicit load. If there are already related entities tracked by the context, they will automatically be attached to any related entity in the context. That means if the Pine tree was already being tracked then as long as the Road is attached to the context, it will see ALL of the related trees in the context, including the Pine that was already there.

If you are using a pattern where you have a short-lived context that is instantiated just to execute the query, then it's not a problem. Most of my architectures are like this. But if you are writing a Windows Form or WPF form and have a context that hangs around, you could run into this problem.

You'll never avoid the problem when the entities are attached to the context.

But here's a twist on the repository method that will return disconnected objects from a context that is managing multiple object.

public List<Road> GetDisconnectedRoadsWithFilteredTrees(string treeFilter)
{
var roadAndTrees = _context.Roads.AsNoTracking()
.Select(r => new
{
Road = r,
Trees = r.Trees.Where(t => t.Description.Contains("Maple"))
})
.ToList();

var rt = new List<Road>();
foreach (var r in roadAndTrees)
{
r.Road.Trees.AddRange(r.Trees);
}
return roadAndTrees.Select(rAt => rAt.Road).ToList();
}

.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }

Downloads for Code First book are online

The downloads samples are available for Programming Entity Framework: Code FIrst on the downloads page of the book's website (learnentityframework.com).

Rowan and I are busy working on the next book (Programming Entity Framework:  DbContext API) right now. Hopefully it will go into production in the next week or two.

Here are links to get a copy of the book:

Programming Entity Framework 2nd edition
From OReilly.com: Ebook (PDF, .mobi, ebook) and print here
Amazon  –> Print  Print version     Kindle:  Kindle Version
Plenty of other sources as well

Programming Entity Framework: Code First
From OReilly.com: Ebook (PDF, .mobi, ebook) and print here
From Amazon: Kindle and print are available: direct link to Amazon page