The Software Devotional

GUID Visualizer Broken in VB.NET and How to Fix It

A colleague brought over a strange problem he was seeing while debugging a VB.NET project. During a debugging session he hovered his mouse over a variable of type System.Guid. You normally expect the standard visualizer for the type to appear, but it was displaying "Empty". Unfortunately, this led to some thrashing and gnashing of teeth because this 'bug' caused him to incorrectly suspect a problem with his code.

After a bit of searching and reflecting over the System.Guid class, I found that it is the visualizer for GUIDs in VB.NET that is 'broken'. The 'bug' exists in both Visual Studio 2005 and Visual Studio 2008. Dang.

Here is what the problem looks like out in the wild. In VB.NET, the visualizer tricks you into thinking that the value of the GUID is Empty.

When you call .ToString on the GUID, there is clearly a GUID populated.

I ran the *same* code in C#, and it works perfectly. +1 for C#!

 

Microsoft left a bug in the two most recent versions of Visual Studio? Not really.

When I found that the GUID shows up correctly when you call the .ToString method, I realized that the GUID is populated, it just doesn't appear correctly in the debugger. This led me to believe that there must be something else going on. I got out Reflector to take a look at the System.Guid class and found the problem.

As it turns out, the System.Guid class contains a single read-only property named Empty. Because the Empty property shows up in the debugger visualizer as the only member, it has the effect of making you think that the value is empty. To make matters worse, the Empty property returns an empty (all zeros) instance of a System.Guid class. The result, when you drill into the System.Guid variable: you get a never-ending tree of what appears to be Empty GUIDs.

We can't blame the visualizer specifically. The word Empty is misleading and leads developers to believe that a GUID variable is empty - the "not used" type of empty.

You can work around this problem by downloading a visualizer for GUIDs (from here and here).  Both of these visualizers give you the option to open a window in the debugger displaying the GUID's value. A little cumbersome.

Here's how you can create an even better GUID debugger visualizer on your own.

Create a VB.NET class library. If you are using Visual Studio 2008, make sure to target the .NET 2.0 framework. Create a new class and put the code below into the class file. The class and project names do not matter.

<assembly: system.diagnostics.debuggerdisplay(="" {tostring}="" ,="" target:="GetType(System.Guid))">
Public Class Visualizer_GUID
    '---- no implementation necessary
End Class

Compile the code and put the output in your "My Documents\Visual Studio 2008\Visualizers" and/or "My Documents\Visual Studio 2005\Visualizers" directories. Crank up another Visual Studio project, create a GUID, and hover over it in debug mode. Here's what you will see.

Now that's much better.

You can download my project and compiled class library here (11.3K).

Free SimpleDB Pricing and Public Beta

Free SimpleDB Pricing Tier

Though the announcement showed up in my mail today, Amazon announced yesterday that a new free pricing tier will be made available for its SimpleDB service. According to Amazon's SimpleDB page, the first 25 machine hours, 1GB of data transfer, and 1GB of data storage used each month will be free of charge for at least the first 6 months (starting Dec 1, 2008).

From Amazon: You can get started with SimpleDB for free and without risk. For at least the first six months of the public beta (starting December 1, 2008), you pay no charges on the first 25 Machine Hours, 1 GB of Data Transfer, and 1 GB of Storage that you consume every month. In most use cases, approximately 2,000,000 GET, QUERY, or QUERYWITHATTRIBUTES API requests can be completed per month before incurring any usage charges. Many applications should be able to operate perpetually within this free tier, such as a daily web-site analysis and traffic reporting tool, a web indexing service, or an analytics utility for online marketing programs.

I have read elsewhere that this process is being spun as a
'trial' for the SimpleDB product. I don't believe that Amazon views this free tier as a traditional trial period and I don't think they are trying to convince more people to help test their software while it is still in beta. It appears to me that Amazon is putting a toe in the water to determine how successful and how costly a free tier might be for SimpleDB. If Amazon can capture the hearts and minds of budding mISVs (when cost is a paramount concern), then they are likely to subsequently capture the pocketbooks of the successful mISVs as well.

In addition to the new free pricing tier, SimpleDB's monthly storage cost per GB has been reduced from $1.50 to $0.25 - 83%.  No doubt, this can be attributed to Google's and Microsoft's plethora of cloud computing announcements this year. Further, at $1.50, SimpleDB's storage cost was way out of line compared with S3's cost of only $0.15 per GB.

Recall that pricing for Amazon's SimpleDB is based on 3 factors: machine utilization, data transfer (in and out), and data storage.  After the first 25 machine hours (free), each machine hour costs $0.14.  The first GB of data transferred in and out are free, and the initial pricing tiers are $0.10 per GB inbound and $0.17 per GB outbound.  After the first GB of storage used per month (free), each additional GB costs $0.25 per month. A rough calculation shows the monthly savings to be a little under $4. Still, many web hosting providers charge several dollars each month for database storage - no need for that any longer.

SimpleDB Enters Public Beta Period

In conjunction with the news of the free pricing tier, Amazon also announced that SimpleDB, while still in beta, is open to all developers. The closed beta, opened to a select group of developers late last year, has given way to a public beta period.

This is good news for me, as I am speaking at VSLive in Dallas next week discussing, among other things, SimpleDB. I despise going to conferences to learn of technologies that have no hope of impacting my development environment for many months or even years to come. There is a time and place for learning how the future will shape up, but for a hands-on coding session, I personally think it best to have the technologies available at my fingertips. This makes SimpleDB available to all the attendees.

The Official Email

Dear AWS Developer,

Amazon SimpleDB is now available in public beta; any business or developer may now sign up and start using this service immediately. Amazon SimpleDB is a web service providing the core database functions of indexing and querying. We're also excited to announce a free tier of usage for SimpleDB, as well as lower prices for storing your data. In addition, Amazon SimpleDB customers will now have access to AWS Premium Support, providing access to a 24/7, one-on-one, fast-response support channel.

Pricing Updates

To help you get started with Amazon SimpleDB, we are providing a free usage tier for at least the next six months. Each month, there is no charge for the first 25 machine hours, 1 GB of data transfer (in and out), and 1 GB of storage that you use. Standard pricing will apply beyond these usage levels, and free usage does not accumulate over time.

In addition, beginning today, Amazon SimpleDB customers will now enjoy significantly reduced storage pricing, only $0.25 per gigabyte-month. This new rate reflects an 83% reduction in storage pricing. For more information, see aws.amazon.com/simpledb.

AWS Premium Support Now Available for SimpleDB

Customers can now also sign up for AWS Premium Support of Amazon SimpleDB. AWS Premium Support offers technical assistance from the Amazon Web Services team whenever and as frequently as customers need it. Whether for operational issues or technical questions, Amazon SimpleDB customers now have access to developer support engineers 24/7, and can count on predictable response time and personalized support. To sign up for AWS Premium Support, visit aws.amazon.com/premiumsupport.

New Features for Amazon SimpleDB Coming Soon

We are also very pleased to announce plans to release two enhancements in the next few weeks that will make Amazon SimpleDB even easier to use. These enhancements will include:

• SQL-like SELECT API: With this feature, you will be able to employ a very familiar SQL-like query language when constructing queries and building applications. The SELECT API will help you be more productive with Amazon SimpleDB right from the start.
• Batch Put: Enables you to streamline the upload of multiple items or attributes, with a single batch API request rather than multiple single item calls.

We are pleased to share these exciting announcements with you, and invite you to visit aws.amazon.com/simpledb for full details.

Sincerely,

The Amazon SimpleDB Team