Why you should use more HTTP.

I am a big fan of Ayende Rahien. He leads Hibernating Rhinos, develops RavenDB, and contributes to NHibernate. Oh, and he is an avid blogger that puts my release schedule to shame.

Ayende recently blogged about over the wire protocol design, and I wanted to echo opinion on this subject!

How to actually send it?

As applications become more complicated they frequently need to communicate with remote resources. So how should your applications talk to each other? If you had not figured it out already: I suggest HTTP!

Why use HTTP?

Here are just a few very small reasons that I love working with HTTP:

• It is supported by every language.
• It is supported by every platform.
• It is supported by every device.
• It has standards for authorization.
• It has standards for encryption.
• It has standard response codes.
• There are amazing tools for it.
• There are more amazing tools for it.
• There are still more amazing tools for it.

...need I go on?

Why NOT use HTTP?

I always look to successful companies for inspiration with technology. If you are making a store front, I suggest you look at Amazon or Newegg. If you are creating social media features, I suggest you look at Facebook or Twitter. If you are designing APIs, I suggest you look at Google. Do you know what Larry Page did not say after Google made it big? "Man, I really wish that we hadn't invested so heavily in all of that web stuff!"

Okay seriously, depending on your application there may be reasons not to use HTTP as your communication protocol. However for the vast majority of applications I think it will do the job, and I strongly urge you to consider using it instead of reinventing the wheel again.

Just my two cents,
Tom

How to use Entity Framework and SQLite

SQLite is the definition of a lightweight database. Using SQLite you can run an entire database with only a 304 KB executable and a database file. It's fast, stable, and very easy to use. Entity Framework is Microsoft's official ORM, and it has support for SQLite!

SQLite Tools

To run SQLite you need only to download the precompiled SQLite binaries for windows:

• SQLite Downloads (Precompiled Binaries for Windows)

You can easily manipulate the database via command line. However, if you would prefer to use a GUI, there is a wonderful Firefox plugin for managing your SQLite databases.

• SQLite Manager (Firefox Addon)

Entity Framework Setup

To get stated using Entity Framework you will need to add two NuGet packages to your solution:

1. EntityFramework
2. System.Data.SQLite (x86/x64)

After that you will need to make sure that your app.config file has properly registered the both a System.Data.SQLite provider and provider factory.

How much does RegexOptions.Compiled improve performance in .NET?

Just how much does the RegexOptions.Compiled flag improve regular expression performance in .NET? The answer: a lot! People have spoken about this before, but below are some more numbers to how you just how much it matters!

Performance Stats

Character Count	Regex Pattern
1	[a-z]
3	[b-y].[1-8]
5	[b-y].[c-x].[1-8].[2-7]
7	[b-y].[c-x].[d-w].[1-8].[2-7].[3-6]
9	[b-y].[c-x].[d-w].[e-v].[1-8].[2-7].[3-6].[4-5]

RegexOptions	1	3	5	7	9
None	234176	285067	653016	690282	687343
Compiled	193945	235213	430609	452483	454625
Percent Gain	17%	17%	34%	34%	34%

.NET 4.5 HttpClient is Thread Safe

Good news everyone, the .NET 4.5 HttpClient is thread safe!

This means that you can share instances of your HttpClients across your entire application. This is useful in that it allows you to reuse persisted connections. One of the best ways to do this is to create a class that can manage the object lifetime of those clients for you.

Below is a simple HttpClientManager that will create one HttpClient per authority. Why per authority? Because you might have to have different settings or credentials for different websites.

Sample Unit Tests

public class HttpClientManagerTests

{

    [Fact]

    public void GetForAuthority()

    {

        using (var manager = new HttpClientManager())

        {

            var client1 = manager.GetForAuthority("http://tomdupont.net/");

            var client2 = manager.GetForAuthority("https://tomdupont.net/");

            Assert.Same(client1, client2);

            var client3 = manager.GetForAuthority("http://google.com/");

            Assert.NotSame(client1, client3);

        }

    }

    [Fact]

    public void TryRemoveForAuthority()

    {

        const string uri = "http://tomdupont.net/";

        using (var manager = new HttpClientManager())

        {

            Assert.False(manager.TryRemoveForAuthority(uri));

            manager.GetForAuthority(uri);

            Assert.True(manager.TryRemoveForAuthority(uri));

        }

    }

}

Web API - Return Correct Status Codes for Exceptions

Returning the appropriate HTTP Response Codes back from your web server is a very important best practice. Fortunately for .NET developers, Web API makes it very easy to use Exception Filters to return the appropriate response codes from your exceptions.

By implementing a custom ExceptionFilterAttribute you can generically create and return HttpResponseMessages for unhandled exceptions based on type. This is great in that you do not have to wrap all of your controller actions in try catch blocks to handle exceptions from other application layers.

Sample Controller

public class ValuesController : ApiController

{

    public string Get(int id)

    {

        switch (id)

        {

            case 1:

                throw new KeyNotFoundException("Hello World");

            case 2:

                throw new ArgumentException("Goodnight Moon");

            default:

                return "value";

        }

    }

}

Web API - Bad Request when Model State is Invalid

When you using Web API, would you like to always return a 400 (bad request) response whenever the model state is invalid? It is easy, just add the following filter attribute to your global list:

[AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, 

    AllowMultiple = false, 

    Inherited = true)]

public class InvalidModelStateFilterAttribute : ActionFilterAttribute

{

    public override void OnActionExecuting(HttpActionContext actionContext)

    {

        if (!actionContext.ModelState.IsValid)

        {

            actionContext.Response = actionContext.Request.CreateErrorResponse(

                HttpStatusCode.BadRequest, 

                actionContext.ModelState);

        }

    }

}

Enjoy,
Tom

AutoCancellationTokenSource

With the following code you can create a CancellationTokenSource that will signal cancellation on dispose. This provides an alternative to having to wrap a normal CancellationTokenSource in a try finally block.

Code

public class AutoCancellationTokenSource : CancellationTokenSource

{

    private bool _isDisposed;

    public AutoCancellationTokenSource()

    {

    }

    public AutoCancellationTokenSource(params CancellationToken[] linkedTokens)

    {

        foreach (var linkedToken in linkedTokens)

            if (linkedToken.IsCancellationRequested)

                TryCancel();

            else

                linkedToken.Register(TryCancel, false);

    }

    protected override void Dispose(bool disposing)

    {

        if (_isDisposed)

            return;

        TryCancel();

        base.Dispose(disposing);

        _isDisposed = true;

    }

    private void TryCancel()

    {

        if (!_isDisposed && !IsCancellationRequested)

            Cancel();

    }

}