Archive for Development category

Anatomy of a good bug report

June 2010 • Development (bug report, bugs) • 2,181 views • 3 responses

Working on the .NET Framework was an interesting but often difficult time especially when dealing with vague or incomprehensible bug reports.

Look before you file

Head to Bing, Google, official support sites and bug database if you have access to it (Microsoft Connect, Apple Radar, Bugzilla for Firefox etc.) to see if others have run into this issue. Searching for the error message can yield good results but remove any elements of the message specific to your project (e.g. class names, property names etc.)

The reasons for this are:

• you may have made a mistake (likely if the software has seen considerable use)
• behave differently to your expectations (the dreaded ‘by design’)
• already be fixed (in the next release and possibly as a patch)
• have an acceptable workaround (why accept a workaround?)

If you are running into problems with developer tools also check out:

• Official forums (MSDN Forums & ASP.NET Forums for Microsoft tools)
• Unofficial respected sites (StackOverflow)

Consider how likely it is you’ve discovered a bug given the complexity of what you are doing, how unusual it is and how mature the software is. Attempting something simple on an established piece of software likely means you’ve made a mistake or misunderstood the documentation.

A good bug report

So you decided to go ahead and report the bug (we all want better software after all).

The essence of a good bug report is having just the right amount of information to identify the bug without any unnecessary detail.

Let’s break it down.

What happened

The most important element is describing what happened and there are four major possibilities.

Error message

You told the software to do something and it displayed an error message instead.

On a good day the error message lets you know why it can’t do what you asked and lets you know what to do to make it work. Given you’re filing a bug report it isn’t one of those days.

The error message is likely cryptic, doesn’t tell you how to get what you want or is just plain wrong. We’ll need that message in its entirety so:

• Copy Windows message box contents as text by pressing control-c when it’s in focus
• When there is a lot of text take a screen print (printscreen on Windows, command-shift-3 on Mac OS X)
• Localized error messages may slow down support responses – switch the app back to their language first

Exceptions

When a piece of a program (called a method or function) can’t do what it claims it throws an ‘exception’ back up to the piece that asked (called) it. This exception is like an error message but with enough lot of technical detail that travels back up the program until something deals with it (known as a catch).

When you see an exception then nothing wanted to deal with it.

You will see an error message that contains the exception and possibly a list of program pieces that couldn’t deal with it. This is called a stack trace and is invaluable to the person investigating your report so include it.

Developers seeing exceptions in their own program need to determine if they should be catching that exception or whether it shouldn’t be occurring. Feel frim the stack trace so your own methods aren’t included but too much is better than too little.

Unexpected behaviour

The software should have done what you wanted but did something you didn’t expect instead.

Report what you thought should happen, what the software did instead, how this is different and the reason why you think it should be that way.

Other people may not agree with your change and in the case of shared programming libraries or frameworks a fix for you can become a break for others that rely on existing behaviour.

Terminated

The software just vanished from the screen without a trace. Crashed, terminated or unexpectedly quit and perhaps took some of your work with it :(

If you’re really unlucky the software that crashed is your operating system. The blue screen of death (BSOD) on Windows, the grey screen on Mac OS X.

Often there are logs left behind you can examine to identify what went wrong.

On Mac OS X fire up Console from Application > Utilities and see what you can find. iPhones, iPods and iPads do this quite often and iTunes will likely offer to send detailed information to Apple who will hopefully share it with the application developer if it’s not their own.

Windows users will want to head to the Event Viewer and find the error and any additional messages that appear to relate to it and included these too.

Steps to reproduce

Ideally the minimal number of steps to reproduce the error every time. You want this to be reliable as possible as companies have limited resources too and won’t spend days trying to reproduce a low-impact bug.

This can be a very important step in understanding the scope of the problem and it’s impact. If you can’t reproduce it in a minimal number of steps there’s always the possibility you’re overlooking some other aspect that could be causing the problem – bad data or rogue code elsewhere!

For an application this may be a data file or a number of manual steps a user must manually perform via the user interface.

For a framework a small self-contained project file with a minimal amount of code to reproduce the failing scenario.

Again here, if you can make the steps clear and ideally in the language of the company producing the software your bug report is not going to hit extra delays.

Environment

Bugs are often sensitive to their environment and you should always include the version number of the software you are using as well as pertinent platform details,  including:

• What operating system, version & service pack
• What processor architecture (x86, x64, IA-64)
• What language & locale your machine is running in (e.g. US English (en-US), Brazil Portuguese (pr-BR))

In the specific case of Visual Studio and .NET bugs:

• What version of Visual Studio you are using (including any service packs)
• What processor architecture you are compiling for
• What language and compiler version you are using (e.g. C# compiling for 4.0)

You may need to include details for your desktop or developer machine and details of the server it is connecting to if any are involved.

What you’ve tried

Chances are you tried several things before filing a bug report. Let us know if you tried:

• Alternate routes through the user interface
• Entering data in a different format or order
• A different computer or environment

Letting them know this means they can avoid suggesting things you’ve already tried or waste time trying them too.

[)amien

Include for LINQ to SQL (and maybe other providers)

May 2010 – February 2012 • .NET (.NET, linq, linq-to-sql) • 12,796 views • 12 responses

It’s quite common that when you issue a query you’re going to want to join some additional tables.

In LINQ this can be a big issue as associations are properties and it’s easy to end up issuing a query every time you hit one. This is referred to as the SELECT N+1 problem and tools like LINQ to SQL Profiler can help you find them.

An example

Consider the following section of C# code that displays a list of blog posts and also wants the author name.

foreach(Post post in db.Posts)
  Console.WriteLine("{0} {1}", post.Title, post.Author.Name);

This code looks innocent enough and will issue a query like “SELECT * FROM [Posts]” but iterating over the posts causes the lazy-loading of the Author property to trigger and each one may well issue a query similar to “SELECT * FROM [Authors] WHERE [AuthorID] = 1″.

In the case of LINQ to SQL it’s not always an extra load as it will check the posts AuthorID foreign key in its internal identity map (cache) to see if it’s already in-memory before issuing a query to the database.

LINQ to SQL’s LoadWith

Most object-relational mappers have a solution for this – Entity Framework’s ObjectQuery has an Include operator (that alas takes a string), and NHibernate has a fetch mechanism. LINQ to SQL has LoadWith which is used like this:

var db = new MyDataContext();
var dlo = new DataLoadOptions();
dlo.LoadWith<Posts>(p => p.Blog);
db.LoadOptions = dlo;

This is a one-time operation for the lifetime of this instance of the data context which can be inflexible and LoadWith has at least one big bug with inheritance issuing multiple joins.

A flexible alternative

This got me thinking and I came up with a useful extension method to provide Include-like facilities on-demand in LINQ to SQL (and potentially other LINQ providers depending on what they support) in .NET 4.0.

public static IEnumerable<T> Include<T, TInclude>(this IQueryable<T> query, Expression<Func<T, TInclude>> sidecar) {
   var elementParameter = sidecar.Parameters.Single();
   var tupleType = typeof(Tuple<T, TInclude>);
   var sidecarSelector =  Expression.Lambda<Func<T, Tuple<T, TInclude>>>(
      Expression.New(tupleType.GetConstructor(new[] { typeof(T), typeof(TInclude) }),
         new Expression[] { elementParameter, sidecar.Body  },
         tupleType.GetProperty("Item1"), tupleType.GetProperty("Item2")), elementParameter);
   return query.Select(sidecarSelector).AsEnumerable().Select(t => t.Item1);
}

To use simply place at the end of your query and specify the property you wish to eager-load, e.g.

var oneInclude = db.Posts.Where(p => p.Published).Include(p => p.Blog));
var multipleIncludes = db.Posts.Where(p => p.Published).Include(p => new { p.Blog, p.Template, p.Blog.Author }));

This technique only works for to-one relationships not to-many. It is also quite untested so evaluate it properly before using it.

How it works

How it works is actually very simple – it projects into a Tuple that contains the original item and all additional loaded elements and then just returns the query back the original item. It is a dynamic version of:

var query = db.Posts.Where(p => p.Published)
   .Select(p => new Tuple<Post, Blog>(p, p.Blog))
   .AsEnumerable()
   .Select(t => t.Item1);

This is why it has to return IEnumerable<T> and belong at the end (and the use of Tuple is why it is .NET 4.0 only although that should be easy enough to change). Not all LINQ providers will necessarily register the elements with their identity map to prevent SELECT N+1 on lazy-loading but LINQ to SQL does :)

[)amien

Creating RSS feeds in ASP.NET MVC

April 2010 – February 2012 • .NET (ASP.NET, atom, mvc, rss) • 18,827 views • 10 responses

ASP.NET MVC is the technology that brought me to Microsoft and the west-coast and it’s been fun getting to grips with it these last few weeks.

Last week I needed to expose RSS feeds and checked out some examples online but was very disappointed.

If you find yourself contemplating writing code to solve technical problems rather than the specific business domain you work in you owe it to your employer and fellow developers to see what exists before churning out code to solve it.

The primary excuse (and I admit to using it myself) is “X is too bloated, I only need a subset. I can write that quicker than learn their solution.” but a quick reality check:

• Time – code always takes longer than you think
• Bloat – indicates the problem is more complex than you realize
• Growth – todays requirements will grow tomorrow
• Maintenance – fixing code outside your business domain
• Isolation – nobody coming in will know your home-grown solution

The RSS examples I found had their own ‘feed’ and ‘items’ classes and implemented flaky XML rendering by themselves or as MVC view pages.

If these people had spent a little time doing some research they would have discovered .NET’s built in SyndicatedFeed and SyndicatedItem class for content and two classes (Rss20FeedFormatter and Atom10FeedFormatter )  to handle XML generation with correct encoding, formatting and optional fields.

All that is actually required is a small class to wire up these built-in classes to MVC.

using System;
using System.ServiceModel.Syndication;
using System.Text;
using System.Web;
using System.Web.Mvc;
using System.Xml;

namespace MyApplication.Something
{
    public class FeedResult : ActionResult
    {
        public Encoding ContentEncoding { get; set; }
        public string ContentType { get; set; }

        private readonly SyndicationFeedFormatter feed;
        public SyndicationFeedFormatter Feed{
            get { return feed; }
        }

        public FeedResult(SyndicationFeedFormatter feed) {
            this.feed = feed;
        }

        public override void ExecuteResult(ControllerContext context) {
            if (context == null)
                throw new ArgumentNullException("context");

            HttpResponseBase response = context.HttpContext.Response;
            response.ContentType = !string.IsNullOrEmpty(ContentType) ? ContentType : "application/rss+xml";

            if (ContentEncoding != null)
                response.ContentEncoding = ContentEncoding;

            if (feed != null)
                using (var xmlWriter = new XmlTextWriter(response.Output)) {
                    xmlWriter.Formatting = Formatting.Indented;
                    feed.WriteTo(xmlWriter);
                }
        }
    }
}

In a controller that supplies RSS feed simply project your data onto SyndicationItems and create a SyndicationFeed then return a FeedResult with the FeedFormatter of your choice.

public ActionResult NewPosts() {
    var blog = data.Blogs.SingleOrDefault();
    var postItems = data.Posts.Where(p => p.Blog = blog).OrderBy(p => p.PublishedDate).Take(25)
        .Select(p => new SyndicationItem(p.Title, p.Content, new Uri(p.Url)));

    var feed = new SyndicationFeed(blog.Title, blog.Description, new Uri(blog.Url) , postItems) {
        Copyright = blog.Copyright,
        Language = "en-US"
    };

    return new FeedResult(new Rss20FeedFormatter(feed));
}

This also has a few additional advantages:

1. Unit tests can ensure the ActionResult is a FeedResult
2. Unit tests can examine the Feed property to examine results without parsing XML
3. Switching to Atom format involved just changing the new Rss20FeedFormatter to Atom10FeedFormatter

[)amien

My top 5 free VS 2010 extension picks

March 2010 – May 2011 • .NET • 23,398 views • one response

The Visual Studio Gallery is already home to 533 tools, controls and templates for VS 2010 and this number is sure to grow once VS 2010 hits RTM and people get to grips with the extendable new editor.

Don’t forget to check out The Visual Studio Blog for more tips, tricks and tools.

Theme VS itself

Color themes for the VS editor have been available and popular for some time but the Visual Studio Color Theme Editor adds colour themes to the VS shell letting you customize it to the most intimate detail as well as providing a bunch of pre-defined themes like Aero and shades of XP.

A bucket and a mop

CodeMaid lets you clean up your code more thoroughly and quickly including removing extra empty lines and whitespace and automatically triggering VS’s cleanup steps too (format document, remove unused strings, sort usings) as well as quick switching between project sub-items, quick-jump to complex methods etc.

Ceasefire on indentation war

The Indentation Matcher Extension detects the indentation style used when you open a file and sets your VS settings to match meaning you can just edit existing projects and solutions without a care in the world.

As it should be – or at least until Elastic tabstops gets ported to VS2010 which might now be possible.

Stylistic comments

My hacked-version of Envy Code R marked italic as bold to trick VS into using it which made a lot of people, myself included, happy. But for those who preferred Consolas it wasn’t much help (there was no way I could redistribute a modified version of Consolas but believe me it looked sweet).

VS 2010 curiously still spurns italic fonts but the pluggable editor means extensions like ItalicComments can get you there although you’ll need to grab the source from gitHub to set it to your coding font of choice given the curious decision to hard-code Lucida Sans.

My Engrish is gud

Until Windows gets an OS-level spell checker (OS X had one in 2000) we’ll have to be content with each major app having it’s own or in the case of VS, none.

The aptly-named Spell Checker extension adds English spell checking to comments, HTML text, strings etc. and you too can avoid embarrassing mistakes preserved in source control for all to see.

[)amien