Month: May 2011

Join us at the Perth .NET user group, June 2nd 5:30pm, where Joe Albahari will showcase the magic of C# 5’s await and async keywords. You’ll see how easy asynchronous programming has become with Microsoft’s latest CTP, and how much you can achieve without being a guru in multithreading or monadic calculus.

We’ll start with very simple examples to introduce asynchronous programming in general: what exactly is it, how does it differ from multithreading, and why do we need it? Then we’ll examine the historical support for asynchronous programming in the .NET Framework and what people are doing right now. You’ll see why BackgroundWorker and the event-based pattern are clumsy and often inadequate – and how the APM strikes fear, pain (and ultimately asynchrophobia) into the hearts of the even most hard-core programmers. We’ll then demonstrate how the async CTP eliminates the problem almost entirely – allowing you to program as you always have.

• TOPIC:  Introduction to C# 5 async with Joe Albahari
• DATE:   Thursday, June 2nd, 5:30pm – 7:00pm
• VENUE: Enex 100 Seminar Room, Level 3, 100 St Georges Terrace, Perth
• COST:   Free. All welcome

There will be plenty of practical examples – from making a rich client app responsive to writing high-concurrency apps and games. We’ll also cover limitations and discuss when you would use this versus Reactive Extensions. The presentation will assume minimum background knowledge and yet will go fairly deep. We’ll also look at what the compiler actually does in translating asynchronous calls, and potential extensibility points. This is a great chance to get to grips with an otherwise difficult-to-research topic.

Joe Albahari is a C# MVP and author of C# 4.0 in a Nutshell and LINQPad. He has presented at TechEd and JAOO, and is a regular speaker in the Perth .NET UG. He has an extensive free online resource on .NET multithreading and parallel programming at www.albahari.com/threading/

I remember Greg Low once talking about the “Resolved: by Design” or “Resolved: as Won’t Fix” replies on Connect when the issue being raised or asked for was clearly a good idea (obviously there are time constraints and sometimes things just aren’t possible); his point was that it doesn’t take too many such responses for even someone evangelical in their conscientious raising of issues to be less than enthusiastic about continuing to do so.

Why do I mention that? Well, ever wanted to mount an .iso file natively in windows? Not such a surprising thing to want to do, right? Especially as Microsoft actually provide many downloads in this format (such as the Windows 7 OS, which is what I was installing). Check out this Connect article “Mount .iso files”. It had 919 up-votes at last count!… Something for Windows 8?

I resorted to using one of the many third party installs which do the job: Virtual CloneDrive. But it really does feel like this should be part of Windows. Getting community/user feedback on your products is a great way to improve them, but only if you’re listening.

“Thank you for your comment/suggestion.
We will continue to monitor your submission and when it reaches the vote threshold from the community we will forward it to the appropriate feature team. We will also respond here to let you know it has been escalated.”

I wonder what that vote threshold is!

Apparently a very good book on ASP.NET MVC 2 is “MVC 2 In Action” from Manning, and while the authors are putting the finishing touches to the MVC 3 version of the book, the entire MVC 2 version is available completely free in Word document form at: https://github.com/jeffreypalermo/mvc2inaction.

Every version of MVC relies on the previous version (except with a few breaking changes), so there is still value in reading this free resource.

Jeffrey Palermo’s original post is here.

Microsoft has made the “Pluralsight On-Demand!” 10 part ASP.NET MVC 3 video training course available free of charge. (“Essential Videos” left-hand pane).

Similarly, there is a 9 part ASP.NET Web Forms 4 video training course also available for free.

This is probably a classic example of if you find you are doing something complicated, there’s almost certainly a better way. It’s also an example of if you think something is genuinely useful and can’t understand why it’s not been implemented already, it probably has but you just haven’t found it yet!

I wanted to get a table’s approximate minimum, maximum and average row size, so after a few attempts I came up with this TSQL snippet:

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declare @schemaname varchar(200) = 'Person'
declare @tablename  varchar(200) = 'Person'

declare @columnList nvarchar(max)
declare @sql        nvarchar(max) 

set  @columnList = 
stuff( 
    (    SELECT
           ' + ISNULL(DATALENGTH(' + c.name + '),0)'
     FROM 
        sys.tables AS t
        INNER JOIN sys.columns c ON t.OBJECT_ID = c.OBJECT_ID 
   where SCHEMA_NAME(schema_id) = @schemaname and t.name = @tablename
    for xml path('') 
    ) 
, 1, 3, '') 

SET @sql = 'SELECT ''' + @schemaname + '.' + @tablename + ''' as TableName,' + 
           ' MIN(' + @columnList + ') AS MinRowLength, ' + 
           ' MAX(' + @columnList + ') AS MaxRowLength, ' + 
           ' AVG(' + @columnList + ') AS AverageRowLength ' + 
           ' FROM [' + @schemaname + '].[' + @tablename + ']'
EXEC sp_executesql @sql

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font-size: small;
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background-color: #ffffff;
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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;
}
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[Note: It’s not 100% accurate due to some row overheads, but it is close enough for many purposes.]

At which point, the thought “Surely there exists a built-in method to do this?” crossed my mind, and of course there is!

If you have sufficient permissions you can quickly produce a min, max and average row size for each table in a database (along with fragmentation information) using

   DBCC SHOWCONTIG WITH TABLERESULTS

It’s not often I don’t have access to the Visual Studio IDE, but I saw Jon Skeet mention this recently on SO: http://ideone.com/

What is ideone?
Ideone is something more than a pastebin; it’s an online compiler and debugging tool which allows
to compile and run code online in more than 40 programming languages.

A big push to move to TFS and away from Visual SourceSafe (strongly resisting urge to berate VSS!)

But what’s this? No event in Perth? Guess that means stick to VSS!! 🙂 (OK, there is a Live Meeting…)

Beth Massi, one of the Program Managers for LightSwitch, has posted a landing page with links for Getting started with Visual Studio LightSwitch.

The links include downloading LightSwitch and the training kit, the forums, and the official LightSwitch Developer Center.

If you were asked where objects greater than or equal to 85,000 bytes are allocated in .NET, you would no doubt say on the Large Object Heap (LOH). What would you say if you were asked where an array of 1000 doubles would be allocated? Currently, as of .NET 4.0, it will be allocated on the Large Object Heap!

William Wegerson (aka OmegaMan), a C# MVP, posted this item to Connect: Large Object Heap (LOH) does not behave as expected for Double array placement that describes and reproduces the behaviour:

byte[] arrayLessthan85K = new byte[84987]; // Note: 12 byte object overhead 84987 + 12 = 84999
Console.WriteLine("byteArrayLessthan85K: {0}", GC.GetGeneration(arrayLessthan85K)); // Returns 0

byte[] array85K = new byte[85000];
Console.WriteLine("byteArray85K: {0}", GC.GetGeneration(array85K)); // Returns 2

double[] array999Double = new double[999];
Console.WriteLine("array999Double: {0}", GC.GetGeneration(array999Double));   // Returns 0
           
double[] array1000double = new double[1000];
Console.WriteLine("array1000double: {0}", GC.GetGeneration(array1000double)); // Returns 2

By looking at the garbage collection generation on object creation (GC.GetGeneration), we can identify if objects reside the LOH or not. If immediately created in generation 2 then that suggests we are in the LOH.

The reason why double arrays with 1000 or more items are allocated on the LOH is performance, due to the fact that the LOH is aligned on 8 byte boundaries. This allows faster access to large arrays and the trade-off point was determined to be 1 thousand doubles.

According to Claudio Caldato, CLR Performance and GC Program Manager, “there’s no benefit to applying this heuristic on 64-bit architectures because doubles are already aligned on an 8-byte boundary”. Subsequent changes have been made to this heuristic that should appear in a future release of the .NET Framework.

As a side note, the expected behaviour is seen if you use Array.CreateInstance() :

// As noticed by @Romout in the comments to that post, the same behaviour is not seen when using Array.CreateInstance()
double[] array1000doubleCreateInstance = (double[])Array.CreateInstance(typeof(double), 1000); // Returns 0
Console.WriteLine("With array-create: " + GC.GetGeneration(array1000doubleCreateInstance));

// Indeed, the expected tipping point into the LOH occurs when using Array.CreateInstance
// (85000 / 8) = 10625, need 12 bytes for object overhead, nearest is 16 (2*8) bytes so effectively 10623 doubles
double[] array1000doubleCreateInstance2 = (double[])Array.CreateInstance(typeof(double), 10623); // Returns 0
Console.WriteLine("With array-create: " + GC.GetGeneration(array1000doubleCreateInstance2));

double[] array1000doubleCreateInstance3 = (double[])Array.CreateInstance(typeof(double), 10624); // Returns 2
Console.WriteLine("With array-create: " + GC.GetGeneration(array1000doubleCreateInstance3));

You probably know this already, but just in case you don’t! If you want line breaks in your popup tooltip descriptions in Visual Studio, you add the element to your XML summary comments e.g.:

/// 
 
/// Main comment 
/// Line 1 
/// Line 2 
/// 
 
public bool SomeProperty { get; set; }

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{
font-size: small;
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font-family: consolas, “Courier New”, courier, monospace;
background-color: #ffffff;
/white-space: pre;/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
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.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 it appears like this: