Xamarin: How to be Successful with Mobile DevOps

The rise of smartphones and changing user behavior over the past seven years have forced organizations to start delivering more and more mobile solutions, with apps a big part of this. There are unique challenges when it comes to enterprise mobile app delivery, however. The ecosystem is fragmented, yet users continue to have high expectations. […]

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Xamarin: Adding Facial Recognition to Your Mobile Apps

Whether it’s automatically tagging friends in our Facebook photos or “live filters” on Snapchat, facial recognition is increasingly becoming a large part of our everyday lives. Adding facial recognition to software in the past was extremely challenging, however. Now, though, Microsoft Cognitive Services makes it as easy as a few lines of code—for free. Whether […]

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Xamarin: Making Your iOS Apps IPv6 Ready

On June 1, Apple started enforcing a new policy whereby all iOS applications must support IPv6-only network services in iOS 9. While Apple states that most apps will not need to be changed or updated, your app may be using a few libraries that need to be updated before you submit your next update. Issues […]

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Wallace B. (Wally) McClure: Golfing for the Peyback Foundation and Children’s Hospital – Results

The Results of the Morning and Afternoon Rounds:

The Morning Results

The Afternoon Results

We had a long and winding day on Monday.  We went and scored the Morning and Afternoon portions of the Children’s Hospital – Peyback Foundation Charity Golf Tournament.  Each portion was flighted.  Pictures were taken of each team while on the course.  The pictures were immediately uploaded to the scoring system for display on the scoreboard.  The flighting of each portion was performed by the application.  As each portion finished, the teams were placed into each flight.  Each team’s scores were shown in the flight as well as the team pictures.

The scoring system is hosted in Azure.  The picture upload is done via an iPhone application written in C#/Xamarin.

I learned a few new things that I will work on and resolve the next time around.

Xamarin: Podcast: WWDC 2016 Recap

This week on the Xamarin Podcast, Pierce and I cover everything you need to know as a mobile developer from Apple’s WWDC 2016, including new additions and upgrades to iOS, macOS, watchOS, and tvOS. Subscribe or Download Today Knowing the latest in .NET, C#, and Xamarin is easier than ever with the Xamarin Podcast! The Xamarin […]

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Greg Shackles: Alexa, Is My Infrastructure on Fire?

I recently broke down and purchased an Amazon Echo after hearing enough good things about it, and also seeing how straightforward it looked to develop for it. It’s no secret that I’m a big fan of Datadog, so naturally I felt like I needed to mix the two. I’ve previously covered exposing Datadog metrics through Hubot, so I figured I’d try to do something similar for the Echo.

I decided to create and host the skill through an AWS Lambda function which made it really easy to get started and deploy. There’s plenty of documentation around on creating skills in Lambda so I won’t really get into that part here. I also went with the Serverless framework to simplify the development and deployment processes, but that’s not actually too important to the implementation here. Ultimately it’s just a simple Lambda function tied to an Alexa skill.

At present, it exposes the current CPU levels of any hosts in your account. For example, saying:

Alexa, ask Datadog to check the CPU

will result in a response along the lines of:

Here are the current CPU loads. Gregs MacBook Pro is at 7%. Gregs iMac is at 4%

I think that’s pretty awesome, so let’s take a look at how to implement it.

Defining the Interaction Model

First we need to definte the skill’s interaction model in Amazon’s developer console.

Intent Schema

The intent schema is the primary manifest of what your skill can do, and how users will interact with it. For this skill we’ll keep it simple and just expose a single intent for querying:

  "intents": [
      "intent": "QueryIntent",
      "slots": [
          "name": "Query",
          "type": "QUERY_LIST"

Eventually it would be great to build this out further and make the skill more conversational and interesting, but this is a sufficient starting point.

Custom Slot Types

In the intent schema you may have noticed the QUERY_LIST type, so now we need to actually define that. This is a custom slot that defines a list of the types of queries we can do. For now it will just contain a single value:

Type Values

This provides a nice place to expose more formal query types as the skill gets extended.

Sample Utterances

Finally, we need to give Amazon a list of sample utterances for the skill in order to teach it how each intent can be interacted with. We’ll give it a few different ways to be invoked:

QueryIntent query {Query}  
QueryIntent check {Query}  
QueryIntent to query {Query}  
QueryIntent to check {Query}  
QueryIntent to query the {Query}  
QueryIntent to check the {Query}  

Implementing the Skill

With all that configuration out of the way, let’s look at the code involved in implementing the skill. Just like in that Hubot plugin I created, we’ll leverage the dogapi package to query the Datadog API. I’ll only include the interesting bits in this post, but the full sample can be found on GitHub.

Talking to Datadog

First, let’s build out a function to query CPU values from Datadog:

import dogapi from 'dogapi';  
import Promise from 'bluebird';

const queryDatadog = Promise.promisify(dogapi.metric.query);

function queryCPU() {  
  const now = parseInt(new Date().getTime() / 1000);
  const then = now - 300;
  const query = 'system.cpu.user{*}by{host}';

  return queryDatadog(then, now, query)
    .then(res => res.series.map(reading => ({
      name: reading.scope
                   .replace(/^host:/i, '')
                   .replace(/(..*$)/i, '')
                   .replace(/W/g, ' '),
      value: reading.pointlist[reading.pointlist.length - 1][1]

Here I’m making use of bluebird, which is a great Promise library that comes with a lot of useful functionality, on top of being very performant. I definitely recommend using this as a replacement for native Promises when working with AWS Lambda functions, as it performs much better and has a significantly lower memory footprint.

There’s not too much to the implementation here. It goes out to Datadog, grabs the latest CPU reading for each host, and then does a little processing on the host name to make it more speech-friendly.

Processing the Intent

When a request comes in for the QueryIntent we defined earlier in the schema, we’ll need to process that. Here’s an example of the type of data that will come in with our intent:

  "session": {
    "sessionId": "SessionId.908e5538-9a5e-4201-b20b-0ed7cc6761bb",
    "application": {
      "applicationId": "amzn1.echo-sdk-ams.app.a5cc355a-042d-4fdc-aabe-afe711657217"
    "attributes": {},
    "user": {
    "new": true
  "request": {
    "type": "IntentRequest",
    "requestId": "EdwRequestId.f01bc54b-6d75-4354-a478-08ec5b3cfed1",
    "timestamp": "2016-06-20T00:11:14Z",
    "intent": {
      "name": "QueryIntent",
      "slots": {
        "Query": {
          "name": "Query",
          "value": "CPU"
    "locale": "en-US"
  "version": "1.0"

Based on that, we can easily implement a function to pull the query value out of the intent and sent it over to Datadog:

function processIntent(intentRequest, session) {  
  const intent = intentRequest.intent;

  if (intent.name === 'QueryIntent') {
    const querySlot = intent.slots.Query;

    if (querySlot.value && querySlot.value.toLowerCase() === 'cpu') {
      return queryCPU().then(readings => {
        const hostSpeechFragments = readings.map(reading =>
          `${reading.name} is at ${reading.value}%`).join('. ');
        const speechOutput = `Here are the current CPU loads. ${hostSpeechFragments}`;

        return buildSpeechletResponse(
          'CPU Load', 

  return Promise.resolve(buildSpeechletResponse(
    'Datadog Query',
    'Sorry, I don't know that query',

Most of that code is around validation and parsing. Once it gets a list of CPU readings it turns them into something readable and forms a spoken response based on them. The buildSpeechletResponse function referenced here is a simple helper method that formats things the way the Alexa API expects them. The code for that method can be found in the helpers file. If we get a query value other than CPU we simply respond saying that we don’t understand that query.

The true at the end of the buildSpeechletResponse signature denotes that each response will end the session with the user. In a more interesting implementation you can imagine keeping the session open and making things more conversational, but for now we’ll keep things as a single operation.

The Handler

Finally, we need to tie it all together and process the incoming request to our Lambda function:

module.exports.handler = function(event, context, callback) {  
    api_key: process.env.DATADOG_API_KEY,
    app_key: process.env.DATADOG_APP_KEY

  if (event.request.type === 'IntentRequest') {
    processIntent(event.request, event.session)
      .then(speechletResponse =>
        context.succeed(buildResponse({}, speechletResponse)));

When a request comes in, we initialize dogapi with our API and app keys, and process the intent. You can specify your own keys by adding them as Serverless variables, such as through the _meta/variables/s-variables-dev.json file, in this format:

  "datadogApiKey": "your-api-key-here",
  "datadogAppKey": "your-app-key-here"

That’s it! The full source for this sample is available on GitHub. It may look like a lot but really it’s very simple to set up Alexa skills, especially when you use AWS Lambda to define them. With just a few lines of code and configuration you can add interactive speech-driven APIs to anything.

Alexa, is that cool or what?

Marcos Cobeña Morián: Si no lo tengo me lo invento

Seguimos con más patrones. En este caso: ¿cómo respondemos ante las necesidades? Solemos tener dos opciones: compramos algo que la solucione o nos inventamos algo que haga lo mismo. No quiero entrar en el punto de vista del consumismo sino de la felicidad. Pero ¿se puede ser feliz resolviendo necesidades? Los términos necesidad y problema… Continue reading Si no lo tengo me lo invento

Daniel Cazzulino: Access Git Information from MSBuild and Code

Why use git information

Regardless of how you generate your version numbers, it’s quite useful to embed
the git repository information in an assembly (and/or its version information),
such as the branch and commit that generated it. It can be invaluable in
troubleshooting issues with a shipped product, and are opaque enough that they
don’t typically represent a secret you would care to hide. Logging code inside
your app/library could also trace this information, so that error logs or crash
reports could include this information too, further facilitating troubleshooting.

In addition, if you’re using GitFlow,
GitHubFlow or some other variation,
your branches or tags may also have additional meaning with regards to versioning,
and thus may also be relevant information you might want to consume as assembly
metadata or directly from code.

Retrieving and using the information

There is of course an infinite number of ways to do this, from powershell that
generate text files with the info, to MSBuild targets that generate JSON files,
continuous integration servers automatically patching files for you or manually
updating a version specifier somewhere in your source tree and having a pre-build
process patch everything locally.

In many cases I’ve seen in the wild, these are intended to be consumed from build
scripts that patch AssemblyInfo.cs files automatically and that’s about it. Maybe
expose some environment variable that you can consume in some way too from those
build scripts. Others would provide format strings and customization hooks to
tweak how the version numbers or assembly info is generated, requiring some
learning on the way. I’ve done so myself too at some point with
SemanticGit. In the case of
it goes to the extreme of being awfully complicated.

I came to the conclusion that for .NET/MSBuild based projects, simple MSBuild
properties populated automatically (such as $(GitBranch), $(GitCommit),
$(GitSha) and the like) coupled with source code exposure of the values via
generated constants, strikes the perfect balance of simplicity and flexibility.

Thus, GitInfo was born.

When you install the package in your project that lives in a git repo, you
automatically get the following MSBuild properties, ready to be consumed
by any target that depends on the provided GitInfo target:

  • $(GitRoot): the root directory (without trailing slash) of the git repository.
    It’s smart enough to also work for submodules, properly returning
    the containing repository root, not the submodule’s.
  • $(GitBranch): the branch being built
  • $(GitCommit): the short (7 chars) commit sha being built
  • $(GitSha): the full commit sha being built

That may be all the information you need if you’re not leveraging the commits
for versioning information. If so, in addition to consuming this from MSBuild
properties you can also consume it from from code (C# and VB projects only
for now). For this, GitInfo leverages a fairly common pattern in the .NET
framework, which is to create a class named ThisAssembly that holds these
values as constants.

For projects with a supported language, GitInfo will generate a partial class
named ThisAssembly in the intermediate output directory, like the following:

namespace Contoso
	/// <summary>Provides access to the current assembly information.</summary>
	partial class ThisAssembly
		/// <summary>Provides access to the git information for the current assembly.</summary>
		public partial class Git
			/// <summary>Branch: master</summary>
			public const string Branch = "master";

			/// <summary>Commit: 5335c2f</summary>
			public const string Commit = "5335c2f";

			/// <summary>Sha: 5335c2f914b56ddd3dab4c0c71b44aa0e070f059</summary>
			public const string Sha = "5335c2f914b56ddd3dab4c0c71b44aa0e070f059";

Notice how the generated values are also exposed as the member summary, so that
from anywhere in your codebase, you can easily find out what the current values
are by just hovering on any code consuming ThisAssembly.Git.Branch for example.

Once thing you don’t want is this fancy addition ruining your carefully tunned
incremental builds, so I’ve been extremely vigilant of that aspect too. The
have been carefully crafted with proper Inputs/Outputs and smart caching of
the git information (you can peek at the GitInfo.cache file in the intermediate
output directory) and refreshing it only when the current git HEAD changes
(i.e. you create a new commit, switch branches, pull commits, create a tag, etc.).

Additionally, this information is (by default) exposed as assembly metadata too
via AssemblyMetadataAttributes which are new in .NET 4.5, as follows:

[assembly: System.Reflection.AssemblyMetadata("GitInfo.Branch", Contoso.ThisAssembly.Git.Branch)]
[assembly: System.Reflection.AssemblyMetadata("GitInfo.Commit", Contoso.ThisAssembly.Git.Commit)]
[assembly: System.Reflection.AssemblyMetadata("GitInfo.Sha", Contoso.ThisAssembly.Git.Sha)]

Leveraging git information for product versioning

It’s quite common to derive a product version number from a branch or tag name
plus the number of commits since the branch/tag was created, SemVer
style. The idea being that if the branch is named ‘v3.0.0’ and there have
been 40 commits to it since it was branched,
then the version number is ‘v3.0.40’. Pretty straightforward and very useful,
since now you can locally build any branch and commit (or tag) and generate a
fully equivalent product (including version!) from what a continuous integration
server would generate. The same technique is usually applied to a version file
in the repository root, which is updated after branching for a release (this is
how most of us do it at Xamarin, for example).

Git can easily tell you how many commits you have made since you created a tag or
branch or since you last commited to a particular file. This means that all the
information to create an automatic version number based on the combination of a
SemVer-named tag/branches (or a version file contents) plus commits on top of
it them readily available. All we need to do is automate its extraction and
expose that information to your code so you can build up whatever version
numbers you wish.

Rather than providing MSBuild properties or scripts with format strings you
have to learn in order to put together your version numbers, GitInfo simply
exposes the determined version-related values via MSBuild and code constants
(through ThisAssembly.Git.BaseVersion and ThisAssembly.Git.SemVer) so
you can freely build the version number you want by just concatenating the
values yourself.

GitInfo exposes two version structures:

  • BaseVersion: this is the base version determined from the branch, tag
    or version file contents. It’s expected to be a SemVer-like format, and
    it’s exposed as its individual components Major, Minor and Patch,
    following SemVer naming conventions.
  • SemVer: this is the determined version obtained by adding the number
    of commits on top of the branch/tag/file, plus any pre-release labels
    specified in the base version (i.e. -pre, -beta). It’s also exposed
    in its individual components Major, Minor and Patch but also adds
    Label (i.e. pre or beta), DashLabel (i.e. -pre or -beta) and
    Source (which can be Branch, Tag or File). The DashLabel allows
    for easily composing a semver string regardless of whether there was a
    pre-release label or not, since it defaults to an empty string if no
    label was found.

In MSBuild, any target that depends on the provided GitVersion target can
access the following properties for the above values:

  • $(GitBaseVersion)
  • $(GitBaseVersionSource)
  • $(GitBaseVersionMajor)
  • $(GitBaseVersionMinor)
  • $(GitBaseVersionPatch)
  • $(GitCommits)
  • $(GitTag)
  • $(GitBaseTag)
  • $(GitSemVerMajor)
  • $(GitSemVerMinor)
  • $(GitSemVerPatch)
  • $(GitSemVerLabel)
  • $(GitSemVerDashLabel)
  • $(GitSemVerSource)

The difference between GitTag and GitBaseTag is apparent in these two
sample values from an actual repo:

  • GitTag: v0.2.63-145-g5335c2f
  • GitBaseTag: v0.2.63

Code like the following is emitted for the ThisAssembly partial class:

  partial class ThisAssembly
    /// <summary>Provides access to the git information for the current assembly.</summary>
    public partial class Git
      /// <summary>Branch: master</summary>
      public const string Branch = "master";

      /// <summary>Commit: 5335c2f</summary>
      public const string Commit = "5335c2f";

      /// <summary>Sha: 5335c2f914b56ddd3dab4c0c71b44aa0e070f059</summary>
      public const string Sha = "5335c2f914b56ddd3dab4c0c71b44aa0e070f059";

      /// <summary>Commits on top of base version: 145</summary>
      public const string Commits = "145";

      /// <summary>Tag: v0.2.63-145-g5335c2f</summary>
      public const string Tag = "v0.2.63-145-g5335c2f";

      /// <summary>Base tag: v0.2.63</summary>
      public const string BaseTag = "v0.2.63";

      /// <summary>Provides access to the base version information used to determine the <see cref="SemVer" />.</summary>      
      public partial class BaseVersion
        /// <summary>Major: 0</summary>
        public const string Major = "0";

        /// <summary>Minor: 2</summary>
        public const string Minor = "2";

        /// <summary>Patch: 63</summary>
        public const string Patch = "63";

      /// <summary>Provides access to SemVer information for the current assembly.</summary>
      public partial class SemVer
        /// <summary>Major: 0</summary>
        public const string Major = "0";

        /// <summary>Minor: 2</summary>
        public const string Minor = "2";

        /// <summary>Patch: 208</summary>
        public const string Patch = "208";

        /// <summary>Label: </summary>
        public const string Label = "";

        /// <summary>Label with dash prefix: </summary>
        public const string DashLabel = "";

        /// <summary>Source: Tag</summary>
        public const string Source = "Tag";

The generated ThisAssembly file is in the intermediate output directory
in a file named ThisAssembly.GitInfo.g.cs (or .vb).

Note that GitInfo hasn’t generated a single [AssemblyVersion] attribute :).
That is intentional! With the above information, you can trivially create one
yourself, share it however you like (linked files, shared asset project, common
targets imported from all your projects, etc.) among your projects. For example,
in Xamarin for Visual Studio, we have a GlobalAssemblyInfo.cs like the

// AssemblyVersion = full version info, since it's used to determine agents versions
[assembly: AssemblyVersion(Xamarin.ThisAssembly.Version)]
// FileVersion = release-like simple version (i.e. 3.11.2 for cycle 5, SR2).
[assembly: AssemblyFileVersion(Xamarin.ThisAssembly.SimpleVersion)]
// InformationalVersion = full version + branch + commit sha.
[assembly: AssemblyInformationalVersion(Xamarin.ThisAssembly.InformationalVersion)]

namespace Xamarin
	partial class ThisAssembly
		/// <summary>
		/// Simple release-like version number, like 4.0.1 for a cycle 5, SR1 build.
		/// </summary>
		public const string SimpleVersion = Git.BaseVersion.Major + "." + Git.BaseVersion.Minor + "." + Git.BaseVersion.Patch;

		/// <summary>
		/// Full version, including commits since base version file, like
		/// </summary>
		public const string Version = SimpleVersion + "." + Git.Commits;
		/// <summary>
		/// Full version, plus branch and commit short sha, like
		/// </summary>
		public const string InformationalVersion = Version + "-" + Git.Branch + "+" + Git.Commit;

You can of course just use the values directly in the version attributes,
rather than having separate constants, for simplicity:

[assembly: AssemblyVersion (ThisAssembly.Git.SemVer.Major + "." + ThisAssembly.Git.SemVer.Minor + "." + ThisAssembly.Git.SemVer.Patch)]
[assembly: AssemblyInformationalVersion (
	ThisAssembly.Git.SemVer.Major + "." +
	ThisAssembly.Git.SemVer.Minor + "." +
	ThisAssembly.Git.SemVer.Patch + "-" +
	ThisAssembly.Git.Branch + "+" +
// i..e ^: 1.0.2-master+c218617

Extending the generated ThisAssembly class with the formatted version strings
is quite useful however, since you can avoid repeating that formatting across your
codebase if you happen to consume it elsewhere, such as in logging.


Being a NuGet package, it’s trivial:

Install-Package GitInfo

If a base version can’t be determined, a warning will be issued and the
version values will default to 0.1.0.


Right after installation, a readme will open up showing the available customization
points via MSBuild, copied here as of this writing:

  $(GitThisAssembly): set to 'false' to prevent assembly 
                      metadata and constants generation.

  $(GitThisAssemblyMetadata): set to 'false' to prevent assembly 
                              metadata generation only. Defaults 
                              to 'false'.
  $(ThisAssemblyNamespace): allows overriding the namespace
                            for the ThisAssembly class.
                            Defaults to the global namespace.
  $(GitDefaultBranch): determines the base branch used to 
                       calculate commits on top of current branch.
                       Defaults to 'master'.
  $(GitVersionFile): determines the name of a file in the Git 
                     repository root used to provide the base 
                     version info.
                     Defaults to 'GitInfo.txt'.
  $(GitInfoReportImportance): allows rendering all the retrieved
                              git information with the specified
                              message importance ('high', 
                              'normal' or 'low').
                              Defaults to 'low'.

  $(GitIgnoreBranchVersion) and $(GitIgnoreTagVersion): determines 
                            whether the branch and tags (if any) 
                            will be used to find a base version.
                            Defaults to empty value (no ignoring).

I find $(GitInfoReportImportance) particularly useful in release

    <GitInfoReportImportance Condition="'$(Configuration)' == 'Release'">high</GitInfoReportImportance>

Which causes the following msbuild log entry:

  Git Info:
    GitRoot:              C:/Contoso
    GitBranch:            master
    GitCommit:            39cf84e
    GitSha:               39cf84eb9027ca669c8aa6cb4fe5f238009d42ba
    GitBaseVersion:       99.0.0
    GitBaseVersionSource: C:ContosoContoso.Version
    GitBaseVersionMajor:  99
    GitBaseVersionMinor:  0
    GitBaseVersionPatch:  0
    GitCommits:           2611
    GitSemVerMajor:       99
    GitSemVerMinor:       0
    GitSemVerPatch:       2611
    GitSemVerSource:      File

This is nice especially if you just do it on the main build script for
a project, which can of course also benefit from GitInfo even without
being a regular project containing code: it just needs to import the
targets and make its targets depend on

But to me the best part is that all of the behavior is implemented in
a single .targets file, with plain native MSBuild with no custom tasks,
even adding the commits to the base patch
so it makes for an interesting read if you’re looking to learn some
MSBuild tricks too :).

Happy MSBuilding!