Scott Hanselman

Back to Basics: C# 4 method overloading and dynamic types

February 12, '10 Comments [30] Posted in Back to Basics | Learning .NET | Programming | VS2010
Sponsored By

C# 3.0 introduced the implicit type "var". I've explained var as saying:

"I'm too lazy to tell you the type of this variable, so you figure it out, compiler."

However, it's more useful than just promoting terseness or laziness:

var i = 10; // implicitly typed
int i = 10; //explicitly typed

Although var is a great way to start arguments about coding standards at your work, there are times when it is required around anonymous types. Here's an example from MSDN:

/ Example: var is required because
// the select clause specifies an anonymous type
var custQuery = from cust in customers
where cust.City == "Phoenix"
select new { cust.Name, cust.Phone };

// var must be used because each item
// in the sequence is an anonymous type
foreach (var item in custQuery)
{
Console.WriteLine("Name={0}, Phone={1}", item.Name, item.Phone);
}

C# 4 (not 4.0, the marketing folks say it's .NET 4, etc.) adds the dynamic keyword. I've explained this saying:

"There's no way for you or I to know the type of this now, compiler, so let's hope that the runtime figures it out."

Here's how this looks from an Intellisense point of view. Here I'm hovering over the dynamic keyword:

dynamiccalc1

And here is the tooltip after pressing "." after "calc."

dynamiccalc2

Now, to the interesting question of the day. Christoff Turner asked this question, essentially:

"I noticed the following while doing some research within C# 4.0:"

using System;
namespace ConsoleApplication1
{
class Program
{
static void f(Int32 x) { }
static void f(dynamic x) {}
static void f(Int32 x, dynamic y) {}
static void f(dynamic x, Int32 y) {}
static void f(Int32 x, dynamic y, Int32 z) {}
static void f(dynamic x, Int32 y, dynamic z) {}
static void Main(string[] args)
{
f(10); // Works - obvious
f(10, 10); // Ambiguous - obvious
f(10, 10, 10); // Ambiguous - not so obvious - since it should be possible to resolve
}
}
}

"Looking at f(10,10,10), what is the reasoning behind this call being ambiguous?"

I stared it it a while longer, then realized what is happening, and called Mads Torgersen to confirm. Mads says this.

In short, the behavior is totally by design:

  • dynamic in method signatures doesn’t come into it: it behaves like System.Object does.
  • Given that, neither of the ternary signatures is better because each fits better than the other on some arguments (Int32 fits 10 better than object does)

The key point here, in bold, because it's significant is: having the type dynamic means “use my runtime type for binding”.

The problem in the context of method calls is that you can't use the runtime type of something until, um, runtime. ;) Binding with dynamic expressions (dynamic binding) happens at runtime.  In this case, we're compiling against method signatures that are known at compile type and we're compiling with a (mostly) static language, so there's no dynamic method dispatching happening that could select a different method overload at runtime.

The dynamic type is statically-typed as dynamic. The compile-time type is "dynamic" (but really it's object, hence the method overloading trouble.)

Another way to look at this is with Reflector. This C# code:

static void f(Int32 x, dynamic y, Int32 z) {}

is essentially this, from a method signature point of view:

static void f(int x, [Dynamic] object y, int z) {}
and if there was a method that returned dynamic, it'd look like this:
[return: Dynamic]
private static object GetCalculator() {}

So, given how dynamic works as a type, how the DLR works in the context of method dispatching, etc, you can see why things didn't work like Christoff thought they would.

Enjoy!

Related Links

About Scott

Scott Hanselman is a former professor, former Chief Architect in finance, now speaker, consultant, father, diabetic, and Microsoft employee. He is a failed stand-up comic, a cornrower, and a book author.

facebook twitter subscribe
About   Newsletter
Sponsored By
Hosting By
Dedicated Windows Server Hosting by SherWeb

The Weekly Source Code 49 - SmallBasic is Fun, Simple, Powerful Programming for Kids and Adults

February 9, '10 Comments [20] Posted in Learning .NET | MSDN | Programming | Silverlight | Source Code
Sponsored By

While the boys are only 2 and 4, I'm always keeping an eye out on new ways to teach them programming. Certainly I hope they'll be more well-rounded and I and spend more time outside, but a even a basic background in programming and logic, I think, produces a more empowered individual.

Created by Vijaye Raji, Small Basic is a simple (only 15 keywords) but powerful environment for getting started programming. Great for kids and non-technical spouses, but powerful enough even for the professional game developer. In fact, Small Basic is probably the fastest and simplest way I've seen yet to produce and publish Silverlight-based games. Read on to see why.

Small Basic is part of MSDN DevLabs and just released version 0.8. It's the eighth installment, but I suspect they are too modest to call it 8.0. ;) It's even internationalized in English, Chinese, French, German, Italian, Japanese, Jorean, Russian, Spanish, Brazilian Portuguese and Turkish...so if you know a computer teacher, you might tell them about this!

Take a look at Small Basic Tetris, for example. You can run it in the browser with Silverlight, right here. The full Small Basic source code for the app is listed right on the page. There's a bunch of great sample Small Basic apps here also.

It has a nice friendly IDE (Integrated Development Environment) with a clever take on Intellisense as seen below. The IDE goes out of its way to give you as much information and context as possible not only with the intellisense "arc" but also context-sensitive help in the right doc.

The Small Basic IDE

Even more clever, I think, is the "Graduate" button that will convert your Small Basic program into Visual Basic for use directly in Visual Studio.

Here's what a Small Basic text mode application would look like:

number = 100
While (number > 1)
TextWindow.WriteLine(number)
number = number / 2
EndWhile

Here's a SmallBasic Windows app:

GraphicsWindow.BackgroundColor = "Black"
GraphicsWindow.Width = 200
GraphicsWindow.Height = 160
GraphicsWindow.PenColor = "Blue"
For i = 1 To 10
GraphicsWindow.PenWidth = i
GraphicsWindow.DrawLine(20, i * 15, 180, i * 15)
EndFor

For those of us old enough to remember learning to program with LOGO and its ubiquitous Turtle, Small Basic includes a Turtle object built in! Remember this?

sides = 50
length = 400 / sides
angle = 360 / sides
Turtle.Speed = 9
For j = 1 To 20
For i = 1 To sides
Turtle.Move(length)
Turtle.Turn(angle)
EndFor
Turtle.Turn(18)
EndFor

Which gives us this image. See the turtle inside?

The LOGO Turtle drawing Circles in SmallBasic

The most amazing part from a learning perspective is the ability to publish your game directly to the Small Basic website and play it or give it to your friends. I hit Publish for this Turtle app and Small Basic - in one click - gave me this link: http://smallbasic.com/program/?WKN265. Now I can send my friends or students to that link.  They can play the game LIVE, see the source listing right there, or even embed it on their own website with included HTML.

I'm really impressed with the amount of though that was put into this app and how easy it was. I hope other folks at Microsoft check it out and appreciate the simplicity.

Related Links

About Scott

Scott Hanselman is a former professor, former Chief Architect in finance, now speaker, consultant, father, diabetic, and Microsoft employee. He is a failed stand-up comic, a cornrower, and a book author.

facebook twitter subscribe
About   Newsletter
Sponsored By
Hosting By
Dedicated Windows Server Hosting by SherWeb

SmallestDotNet Update - Now with .NET 4 support and an includable JavaScript API

February 9, '10 Comments [15] Posted in ASP.NET | ASP.NET MVC | Javascript | Learning .NET | Microsoft | Source Code | Tools | VS2010 | Windows Client | WPF
Sponsored By

A few years back I wrote a post on the size of the .NET Framework. There's historically been a lot of confusion on the site of the .NET Framework. If you search around on the web for ".NET Framework" or ".NET Framework Redistributable" you'll often get a link to a 200 meg download. That download is the complete offline thing that developers redistribute when they want to install the .NET Framework on any kind of machine without an internet connection.

The .NET 3.5 Client Profile is more like 28 megs and the .NET 4 Client Profile is a looking smaller than that, in fact. Back then I made this website,SmallestDotNet.com to help out. It'll sniff your browser's UserAgent and tell you want version of .NET you have, how big the download would be to get you to .NET 3.5 and what .NET redistributable is best for you in order to minimize your download.

Now that the .NET Framework 4 is coming out soon, I took an hour and updated it (with Tatham Oddie's help, as he's staying over at the house this week) to support the new framework. We also added a few bug fixes (and I'm sure, a few bugs) and a simple Javascript API to help you detect the .NET Framework on the client side.

You can use the site in three ways.

First, visit the site.

If you've got a machine you want to install .NET on, or you're not sure what version it has, just visit SmallestDotNet.com and I'll do my best to tell you. It works best on IE, but it'll also work on Firefox if you've got the .NET add-on. If you've got Safari or Chrome, I'll apologize but I can't help you as those browsers don't tell me anything about .NET.

Second, include the Javascript that spits HTML.

If you want to tell the user what version of .NET they have with minimal effort and you want to do it on your site, perhaps via your blog, you can just include this line:

<script type="text/javascript" src="http://www.smallestdotnet.com/smallestdotnet/javascript.ashx"></script>

and I'll return something like:

document.write('<span class="smallerdotnet">')
document.write('Detected 3.5 SP1 .NET Framework. No update needed.')
document.write('</span>')

and you can style to taste.

Third, include the Javascript that spits JSON.

The HTML spitter is fast, but less useful if you like control over things. Like, um, text. So, you can include:

<script type="text/javascript" src="http://www.smallestdotnet.com/smallestdotnet/javascriptdom.ashx"></script>

and I'll spit out a JSON object like this:

SmallestDotNet = {};
SmallestDotNet.latestVersion = {
major: 4,
minor: 0,
profile: "client",
servicePack: null
};
SmallestDotNet.allVersions = [
{
major: 4,
minor: 0,
profile: "client",
servicePack: null
},
{
major: 3,
minor: 5,
profile: "full",
servicePack: 1
},
{
major: 2,
minor: 0,
profile: "full",
servicePack: null
}
];

We'll put out the latest version of the .NET framework on the machine, as well as its Service Packs, and its profile (client profile, full, etc) if appropriate. It'll also give you an array of ALL the versions of the .NET Framework it finds on the machine. In my example, it says my machine has .NET 4 Client Profile, .NET 3.5 SP1 and .NET 2.0.

UPDATE: I've updated the JSON output to return another array with a complete list of all available .NET Frameworks and the URL they can be downloaded from, something like this:

SmallestDotNet.downloadableVersions =
[{
major: 4,
minor: 0,
profile: 'client',
servicePack: null,
url: 'http://www.microsoft.com/...'
},
...SNIP...

{
major: 2,
minor: 0,
profile: 'full',
servicePack: 2,
url: 'http://www.microsoft.com/...'
},{
major: 1,
minor: 1,
profile: 'full',
servicePack: 1,
url: 'http://www.microsoft.com/...'
}];

I currently don't go into deep deep detail, like .NET 2.0 SP2, etc, but if you want that functionality, let me know and I can add it. This is a spike (ongoing for two years, actually) so if it's useful, let me know. If it's missing something, let me know.

From this JSON, you can ask all sorts of questions. Here's a JavaScript alert() example that would work on this JSON object. Of course, you should check things for null, as well as check the length of allVersions.

alert( SmallestDotNet.latestVersion.major ); 
alert( SmallestDotNet.allVersions.length );
alert( SmallestDotNet.allVersions[0].minor );
alert( SmallestDotNet.allVersions[1].major );");

It'd be cool to add some jQuery love to this and use it to give and end-user some nice feedback on what version of your application to install, or what version of .NET they should install first. It could also be useful for self-troubleshooting your application.

Hope this is useful. Enjoy.

About Scott

Scott Hanselman is a former professor, former Chief Architect in finance, now speaker, consultant, father, diabetic, and Microsoft employee. He is a failed stand-up comic, a cornrower, and a book author.

facebook twitter subscribe
About   Newsletter
Sponsored By
Hosting By
Dedicated Windows Server Hosting by SherWeb

Hanselminutes Podcast 199 - How Craigslist Works - with Jeremy Zawodny

February 6, '10 Comments [2] Posted in Open Source | Podcast | Source Code
Sponsored By

Jeremy Zawodny My one-hundred-and-ninety-ninth podcast is up. I chat with Jeremy Zawodny, a developer at Craigslist on how the system is put together. How many servers do they have? How does it all fit together and what are the major technology problems they have to solve?

Subscribe: Subscribe to Hanselminutes Subscribe to my Podcast in iTunes

Download: MP3 Full Show

Links from the Show

Do also remember the complete archives are always up and they have PDF Transcripts, a little known feature that show up a few weeks after each show.

Telerik is our sponsor for this show.

Building quality software is never easy. It requires skills and imagination. We cannot promise to improve your skills, but when it comes to User Interface and developer tools, we can provide the building blocks to take your application a step closer to your imagination. Explore the leading UI suites for ASP.NET AJAX,MVC, Silverlight, Windows Forms and WPF. Enjoy developer tools like .NET reporting, ORM, Automated Testing Tools, TFS, and Content Management Solution. And now you can increase your productivity with JustCode, Telerik’s new productivity tool for code analysis and refactoring. Visit www.telerik.com.

As I've said before this show comes to you with the audio expertise and stewardship of Carl Franklin. The name comes from Travis Illig, but the goal of the show is simple. Avoid wasting the listener's time. (and make the commute less boring)

Enjoy. Who knows what'll happen in the next show?

About Scott

Scott Hanselman is a former professor, former Chief Architect in finance, now speaker, consultant, father, diabetic, and Microsoft employee. He is a failed stand-up comic, a cornrower, and a book author.

facebook twitter subscribe
About   Newsletter
Sponsored By
Hosting By
Dedicated Windows Server Hosting by SherWeb

Installing and Setting Up and Encoding for IIS 7 Smooth Streaming and Silverlight

February 5, '10 Comments [25] Posted in ASP.NET | IIS | Silverlight
Sponsored By

I heard someone saying they were having trouble setting up Smooth Streaming for IIS, so I wanted to try it myself.

If you just want to see Smooth Streaming work, visit http://www.smoothhd.com/ for some sample demos. They'll adapt to your bandwidth and look as nice as they can. If you want to fake a low-bandwidth situation, you can use the player at http://www.iis.net/media/experiencesmoothstreaming and play with limiting the bit rate.

Step 0: Got IIS?

I've got IIS 7 because I've got Win 7. If your Win 7 installation doesn't have IIS yet, go to Programs and Features and click "Turn Windows Features On or Off" and select Internet Information Services. Don't forgot to go through the tree and turn on the things you want, like "Static Content" in this case. (Remember, if you've just installed IIS, shut down Skype as it grabs port 80 if it gets there first. Lame.)

Step 1: Add IIS Media Services

I'm running Windows 7 x64 so I installed IIS Media Services 3.0 64-bit, but you can certainly install IIS Media Services for 32-bit also. Even easier, just install it from the Web Platform Installer directly.

IIS Media Services 3.0 Setup

Installing the IIS Media Services pack gives you a new icons in the IIS manager:

image

Step 2: Get (or Make) Some Content (and Encode It)

If you just want to see this work, you can get some pre-encoded content, below in 2a. Later in 2b, I'll encode some new content.

Step 2a: Get Some Pre-Encoded Content to Test

Use At this point, if you're just testing, you can go download the pre-encoded "Buck The Bunny" HD Video Sample Content (about 500 megs of HD video). Run it, extract the files, and put them somewhere like c:\inetpub\wwwroot\bunny.

HOW SMOOTH STREAMING WORKS - SIDE NOTE: You kind have to see it to get it, but it's actually clever in its simplicity. Some folks freak out when they take a, say, 200 meg video file and encode it for Smooth Streaming and the resulting directory is, say, 500 megs. They might say, it's larger! I don't have that kind of bandwidth! In fact, less is sent over the wire than exists on disk. The idea is that Smooth Streaming creates "steps" of bitrates. It encodes and stores your file multiple bit-rates on the disk.
To illustrate this, I will use the DJ Hero video game as an example: Picture of the tracks on the record in DJ Hero as the DJ moves between tracks
Just as the DJ moves between tracks depending on how the crowd feels, Silverlight between encoded streams depending on the bandwidth is doing. Remember, it's called "Adaptive" Smooth Streaming.

Now I visit http://localhost/bunny/default.html and rather than the standard Silverlight Player, I'm going to select one called "User Experience Simulator." Basically, I want to fake a low bandwidth situation and see the Smooth Streaming react.

NOTE: If you like, or you're demoing this to a boss or someone, there's a prettier/shinier player on the Smooth Streaming Sample Content page that you can swap out. Details on the Getting Started Page for Smooth Streaming.

I start the player, and you'll notice on teh right side there's "Now Downloading" and "Max Bit Rate." I'll force a lower bit-rate (again, I'm simulating congestion here) and seek within the video. Then raise it, and wait, or seak. Notice the chart showing that the Silverlight Player "switched tracks" without dropping frames.

Another metaphor would be changing gears on a bicycle to adapt to a changing road.

Big Buck Bunny in Silverlight Smooth Streaming

Step 2b: Encode Some Content of Your Own.

Ok, so that was just existing content. You can download Expression Encoder 3.0 and encode all the video you want, but if you want to encode Smooth Streaming or H.264, you have to upgrade for $49 to Expression Encoder 3.0 with IIS Smooth Streaming. (By the way, Expression Encoder will also do Screen Capture, which is nice to know. The free version will do up to 10 min of Screen Capture, which is also useful to know.)

I drag a video of ScottGu in HD into the Encoder and select IIS Smooth Streaming. Since my source is HD 720p, I'll select that. By default, the profile will basically encode a high version and low version, but for best results you'll want to decide how many levels of stepping you want. Expression Encoder can be run in a batch from the command-line also, BTW.

Make sure you click the encoding option you want, right-click and say "Apply to Selected Items." You'll know you got it right if the Video section further down (that you can open up) includes multiple streams of various sizes and bitrates. Notice the screenshot. More streams will mean longer encodes and more space on disk taken up, BUT it'll make for more bitrate options for the player to choose and a MUCH better, smoother experience. Again, you might have 1, 5 or 10 streams for a 1 gig source and end up using 5+gigs of space on disk (I made those numbers up) but the end user's experience will be smooth and the bandwidth used will be as small as possible.

Microsoft Expression Encoder 3

It is worth noticing that screencasts should mostly be encoded using an H.264 Screen Encoding profile, while action like sports games work better with other codecs. What looks good on the football field often looks like crap if it's some dude coding on his screen. You'll also want to have a reasonable minimum resolution and a minimum bitrate. Experiment and you'll find what works and save it as a custom profile that's right for your content.

After I encoded all this, I thought to myself, crap, the REALLY LOW bandwidth version is not acceptable. Do I have to re-encode to not include that one? I can just hack the .ism file manifest as it's just XML and remove all knowledge of that lower bit-rate file. UPDATE: There's a nice UI to managed rethe different bit rates, so no need to hack any XML.

It can be tricky to do the math and figure out what resolutions and bitrates to use for your smooth streaming content so you can use this Silverlight-based Smooth Streaming Multi-Bitrate Calculator. There's a WPF one also. To get really good quality you'll vary not only the bitrate, but also the resolution (but you'll stretch it, so the user won't know the resolution changed also.) Ultimately you have complete control as everyone's content has different needs.

The "More Info Than You Asked For" Section: What's Really Happening?

If you want a deep deep dive into what's going on, check out the Smooth Streaming section of Alex Zambelli's blog. It's wonderfully deep. A lot of people don't realize that Smooth Streaming is still just plain HTTP.

Traditionally streaming is a long running stream over a stateful protocol, where a packet is a some milliseconds of video.

Smooth_Slide06

Adaptive Streaming is chunked over HTTP where the client can choose different chunk sizes in various bit rates.

 

Smooth_Slide08

From Alex's blog:

A typical Smooth Streaming media asset therefore consists of the following files:

  • MP4 files containing video/audio
    • *.ismv – contains video and audio, or only video
      • 1 ISMV file per encoded video bitrate
    • *.isma - contains only audio
      • In videos with audio, the audio track can be muxed into an ISMV file instead of a separate ISMA file
  • Server manifest file
    • *.ism
    • Describes the relationships between media tracks, bitrates and files on disk
    • Only used by the IIS Smooth Streaming server – not by client
  • Client manifest file
    • *.ismc
    • Describes to the client the available streams, codecs used, bitrates encoded, video resolutions, markers, captions, etc.
    • It’s the first file delivered to the client

Both manifest file formats are based on XML. The server manifest file format is based specifically on the SMIL 2.0 XML format specification.

With IIS7 Smooth Streaming, a client is expected to request fragments in the form of RESTful URLs:

http://video.foo.com/NBA.ism/QualityLevels(400000)/Fragments(video=610275114)

http://video.foo.com/NBA.ism/QualityLevels(64000)/Fragments(audio=631931065)

The values passed in the URL represent encoded bitrate (i.e. 400000) and the fragment start offset (i.e. 610275114) expressed in an agreed-upon time unit (usually 100 ns). These values are known from the client manifest.

But most importantly, therefore I make it bold and in red so you'll read it twice:

...what about dynamic bitrate switching that makes adaptive streaming so effective? This part of the Smooth Streaming experience is implemented entirely in client-side Silverlight application code – the server plays no part in the bitrate switching process.

An important thing to think about when doing network capacity planning is that in a traditional scenario, clients will drop to the bit rate they can sustain on average. In Smooth Streaming, it will continually hop up to the highest they can handle. Smooth Streaming gives each client the highest quality video they can handle. That may result in some network stress for the video provider and network infrastructure if you were expecting video that was less than awesome. ;)

Shiny.

A Q&A from Alex's Smooth Streaming FAQ

Q: Is Smooth Streaming based on Microsoft’s ASF file format? Or does it use some new proprietary file format?
A:
No, the Smooth Streaming File Format is based on the ISO-standardized Base Media File Format, better known as the MP4 file format. It follows the ISO/IEC 14496-12 specification

Q: Will Smooth Streaming ensure I can deliver HD video to all my customers?
A:
No. Smooth Streaming can’t perform any miracles; it’s simply an enhanced HTTP delivery method. Delivery of HD video is still bound by the efficiency of the codecs used: VC-1, H.264, etc. For example, most video experts would agree that 720p/24 video can’t be delivered at a satisfactory quality level with less than 2 Mbps encoded bitrate. Well, 2 Mbps of encoded video still requires 2 Mbps of network bandwidth in order to be delivered in real-time – and there’s nothing IIS7 or Silverlight can do to change that.

Q: Where can I see Smooth Streaming in action?
A:
Visit SmoothHD.com for a demo of on-demand Smooth Streaming, with video content ranging up to 720p HD for those on fast connections (3 Mbps or more). Also check out the IIS.net demo which lets you simulate variable network bandwidth during playback. The only requirement to view Smooth Streaming video is a Silverlight 2 (or better) browser plugin. For a demo of live Smooth Streaming, check out Home Shopping Network’s 24-hr live shopping channel, also offering up to 720p in full-screen mode.

Conclusion

It's really easy to setup and easy to encode for Smooth Streaming. In my case, I just encoded the files off my HD video camera. You'll see more Smooth Streaming around various Microsoft sites that serve video in the coming months.

Have fun!

Related Links

About Scott

Scott Hanselman is a former professor, former Chief Architect in finance, now speaker, consultant, father, diabetic, and Microsoft employee. He is a failed stand-up comic, a cornrower, and a book author.

facebook twitter subscribe
About   Newsletter
Sponsored By
Hosting By
Dedicated Windows Server Hosting by SherWeb

Disclaimer: The opinions expressed herein are my own personal opinions and do not represent my employer's view in any way.