Failure to start Xamarin Android Player simulator

On Windows 10, you might find that after installing Xamarin tools and the Xamarin Android Player you can’t launch the simulator from Visual Studio nor the Xamarin Device Manager with the error ‘VBoxManage command failed. See log for further details‘.

xap failure

XAP is automating VirtualBox in the background, but you’ll probably find that you can’t manually start the VM image from there either, but with a more helpful error ‘Failed to open/create the internal network‘ and ‘Failed to attach the network LUN (VERR_INTNET_FLT_IF_NOT_FOUND)‘:

xap failure - vbox

The fix is to edit the connection properties of the VirtualBox Host-Only network adapter (as named in the error message) and make sure that VirtualBox NDIS6 Bridged Networking Driver is ticked. In the example below, even though the installation appeared to go swimmingly it didn’t enable the bridge driver.

xap failure - fix

Tick the box and off you go!

Chutzpah and source maps – more complete TypeScript/CoffeeScript coverage

I spent a lot of time over Christmas contributing to open-source JavaScript unit test runner Chutzpah, and the recent Chutzpah 3.3.0 release includes source-map support as a result.

The new UseSourceMaps setting causes Chutzpah to translate generated source (i.e. JavaScript) code coverage data into original source (i.e. TypeScript/CoffeeScript/whatever) coverage data for more accurate metrics. It also plays well with LCOV support, which I added a while back but only got released as part of 3.3.0.

Chutzpah before sourcemaps

Chutzpah handles recording code coverage using Blanket.js. However, code coverage was always expressed in terms of covered lines of generated JavaScript, and not covered lines of the original language.

This makes code coverage stats inaccurate:

  • There’re likely to be more generated JavaScript lines than source TypeScript/CoffeeScript (skewing percentages for some constructs)
  • The original language might output boilerplate for things like inheritance in each file, which if not used is essentially uncoverable in the generated JavaScript – TypeScript suffers especially from this

UseSourceMaps setting

The new UseSourceMaps setting tells Chutzpah to, when faced with a file called File.js, look for a source map file called containing mapping information between File.js and its original source code – likely a TypeScript or CoffeeScript file.

 "Compile": {
   "Extensions": [".ts"],
   "ExtensionsWithNoOutput": [".d.ts"],
   "Mode": "External",
   "UseSourceMaps": true
 "References": [
   {"Include": "**/src/**.ts", "Exclude": "**/src/**.d.ts" }
 "Tests": [
   { "Include": "**/test/**.ts", "Exclude": "**/test/**.d.ts" }

This will only be of use when Chutzpah has been told of original source files using the Compile setting, asked to perform code coverage and source maps exist.

Parsing source maps in .NET

When we minify JavaScript source, or write code in TypeScript or CoffeeScript and compile it down to JavaScript our debugging experience would be difficult without tools that support source maps.

I’m currently modifying Chutzpah to address a tiny gap in its handling of code coverage for generated source files like those output by the TypeScript compiler, and needed exactly that – a way for .NET code to parse a source map file, then query it to find out which original source line numbers map to a generated source line that’s been covered or not by a unit test.

SourceMapDotNet is my initial, bare-bones attempt at a partial port of the the excellent Mozilla source-map library, but intended only to handle that one type of query – not full parsing, definitely not generation.

It’s also up on NuGet.

SonarQube TypeScript plugin

I use SonarQube (live demo) a fair bit to monitor code quality metrics, but there’s no in-built support nor published community plugins for TypeScript analysis – so I’m writing one.

I intend two core features:

  • Measure code quality by running against TsLint
  • Measure unit test coverage by processing an LCOV file
Running an alpha version of SonarTsPlugin against a random TypeScript project from GitHub shows code issues but no code coverage - yet

Running an alpha version of SonarTsPlugin against a random TypeScript project from GitHub shows code issues but no code coverage – yet

The first of those two goals isn’t that far away at all – above is a screenshot from the alpha version running locally. If you’re interested in helping, drop me an email!

TypeLite 0.9.6 out with multidimensional arrays fixed

I use Lukas Kabrt’s TypeLITE package (NuGet link) a lot to automatically generate TypeScript interfaces from .NET classes and interfaces, so occasionally I’ll drop a pull request to fix the odd issue in its backlog when I’ve got a spare hour (though generally they’re not issues I encounter myself).

0.9.6 includes a patch I submitted to fix jagged array output. Before, the following situations wouldn’t be processed correctly and they’d all output a single-dimensional array:

public string[][] MyJaggedArray { get; set; }
public string[][][] MyVeryJaggedArray { get; set; }
public IEnumerable<string> MyIEnumerableOfString { get; set; }
public List<string> MyListOfString { get; set; }
public List<string[]> MyListOfStringArrays { get; set; }
public List<IEnumerable<string>> MyListOfIEnumerableOfString { get; set; }
public List<List<string[]>> MyListOfListOfStringArray { get; set; }

Processing used to just stop once it detected an array-ish type (which oddly didn’t include IEnumerable), without diving deeper. For jagged arrays the logic’s pretty straightforward, as you can just look at the rank of the array type and output that many pairs of square brackets.

For enumerable types things are a bit more interesting as we have to read into the generic type parameter recursively. Now the above gets formatted as you’d expect, and another issue’s closed off.

MyJaggedArray: string[][];
MyVeryJaggedArray: string[][][];
MyIEnumerableOfString: string[];
MyListOfString: string[];
MyListOfStringArrays: string[][];
MyListOfIEnumerableOfString: string[][];
MyListOfListOfStringArray: string[][][];

gh-ticker – a simple ticker for your public GitHub activity

With a spare weekend I put together the ticker widget you can see at the top of the screen just now – iterating through my most recent GitHub activity items every few seconds.

It is, fittingly, available on GitHub for forking and customisation licensed under the BSD 3-Clause.

How it works

The GitHub API is very straightforward, and data that’s already public (such as what appears on your Public Activity tab) can be accessed without authentication and with JSONP – ideal for client-side hackery.

The widget’s architected as a couple of JS files (taking a dependency on jQuery and Handlebars for now), one which contains Handlebars precompiled templates and the other that makes the API call and renders partials befitting the type of each activity item.

Setting it up’s pretty simple – reference the JS and CSS, make sure Handlebars and jQuery are in there too and then whack a DIV somewhere on your page with id ‘gh-ticker’.

<div id="gh-ticker" data-user="pablissimo" data-interval-ms="5000" />

The user whose data is pulled and the interval between ticker item flips are configurable as data attributes.

The GitHub Events API

The Events API knows about a set number of event types – for each event type, there’s a Handlebars partial. When we’re wondering how to render an item we look up the relevant partial and whack it into the page.

Since that’s a fair few partials (neat for development in isolation, bad for request count overhead) those partials are precompiled using the Handlebars CLI and put into a single gh-templates.js file.


The ticker’s very basic – it just hides or shows the items as required, without any pretty transitions. It also takes a dependency on jQuery which it needn’t, since it’s only using it for the AJAX call and element manipulation both of which are easily covered off by existing browser functionality.

Still – it can be easily styled to be fairly unobtrusive and has at least taught me a little about Handlebars.

NRConfig for New Relic released

I’ve spent a little time working on NRConfig, the tool that generates custom instrumentation files for .NET projects using New Relic, after a bug report that pointed out that the tool was unable to run for an assembly for which dependencies weren’t available. This isn’t likely in production code as you’d likely need the dependencies available to run, but can happen when you want to do an offline run of instrumentation generation against a third-party library.

To this end, NRConfig’s been changed pretty substantially under the hood to support alternatives to .NET reflection for discovering instrumentable types, and Microsoft’s Common Compiler Infrastructure (or CCI) library drafted in as the default discovery provider.

CCI’s slower than reflection by quite a margin – it can now take several seconds to produce instrumentation configuration for large or complex assemblies, but I’m hoping to improve that if it becomes a problem.

Also introduced is support for MSBuild in a new NuGet package, NRConfig.MSBuild. This should make generating instrumentation files for your own code a lot less work – simply add the NRConfig.MSBuild package to any project containing code you want to instrument and mark up the assembly, types or methods with [Instrument] attributes to control the output. On build, a custom instrumentation file is generated in your output directory for you to deploy wherever.

Enabling CORS on your ASP.NET output-cached webservice? Don’t forget to change your varyByHeaders…

If you’re enabling CORS on your ASP.NET web service, you’ll be receiving an ‘Origin’ header and outputting an Access-Control-Allow-Origin header if you’re happy to receive the request. If you’re being strict about your access control policy, you’ll be returning the same origin you got rather than * so that the user agent knows to let the call continue.

This poses a bit of an obstacle when combined with ASP.NET Output Caching, as unless you either tell it to vary its output by all headers or explicitly call out the Origin header you may find that accessing your service from two URLs within your cache lifetime period will see one call succeed and the other fail.

The failing call is because the Access-Control-Allow-Origin header’s being sent from the cache, but for the broken site won’t match the Origin that was sent to it and since we’ve not configured output caching to vary by the Origin header it assumes the requests from the two different origins are the same and responds accordingly.So, we just need to tack in the Origin header into our cache configuration’s varyByHeader attribute (separated from other headers with a semicolon, if any others exist) and bingo! The two sites result in correct responses.


LinqPad, Azure Table Storage Driver and continuation tokens – or ‘how to get more than 1000 results/run a query that runs for more than 5 seconds’

Mauricio Diaz Orlich made a LinqPad storage driver that lets you query Azure Table Storage as easily as any other data-source within LinqPad – this is invaluable when working with Azure as there aren’t any real alternatives when you just want to make an ad-hoc query or make multi-table queries.

However, there’s an issue – the driver doesn’t use continuation tokens internally so your query needs to both finish executing within the Azure Table Storage limit of 5 seconds and return fewer than 1000 results, otherwise you’ll be missing data and won’t necessarily notice.

I forked the source to see if I could patch in a way around it but in doing so found a much simpler solution – do exactly what you’d do in your .NET code and call the AsTableServiceQuery() extension method on your query before you materialise it.

For example:

.Where(x => x.EmailAddress == "")

This query will now return as many results as exist (up to LinqPad’s seemingly unavoidable 10,000 record limit) and will execute for as long as it takes to actually return all results by way of continuation tokens.

Visual Studio Azure Deployment Error: No deployments were found. Http Status Code: NotFound

Had this recently while deploying to Azure, to the blank staging slot of a cloud service that already had a production instance running.

Looking at the log, immediately before the error Visual Studio claimed that it was stopping a role – how can that be, when the staging slot’s already free? This is another situation where you shouldn’t believe Visual Studio’s lies – upload the package directly to the portal in the event of failure and you’ll generally get better and more accurate errors.

The issue in this case? We’d run out of spare cores in our subscription to deploy two medium instances of the application to staging. Why does the error talk about missing deployments (and try to stop non-existent deployments in this instance)? Unknown.