Creating a yaml CI Build for .net application

One of the great announcements from this year's Microsoft Connect() conference was YAML support for VSTS build definitions. 

For me, it's a great way forward towards "codifying" the build pipeline. The current TFS builds technology, introduced in Team Foundation Server 2015, despite all the benefits of a loose and extensible mechanism is rather difficult to maintain as code and doesn't really fit "pipeline as a code" definition. If you remember, earlier versions of Team Foundation Server (TFS 2005 and TFS 2008) used an MSBuild file to run builds. Whilst this was easy to code and maintain, extensibility was rather limited. Then, Team Foundation Server 2010 introduced XAML builds with better support for workflows but was difficult to work with. TFS 2015 simplifies XAML but the whole logic is spread across different aspects of the build. Yaml solves this shortcoming nicely.

Enable YAML Builds Preview Feature

At the time of writing this post, support for YAML builds is still in preview in VSTS. To enable it for your account, click on your profile and select option "Preview Features" from the drop down menu

Select option "from this account [projectName]". Scroll down till you find the "Build Yaml definitions" feature and set it to On

We are now ready to use YAML builds.

Creating a Yaml Build 

There are two ways in which we can set up a Yaml build. 

1) Create a file called .vsts-ci.yaml. When you push your change with this file to TFS, a build definition, using this file is created for you.

2) Explicitly create a build definition using the YAML template, providing the path of YAML file that you have committed in the repo.

We will go with option 2.

Create build.yml file

YAML file format is the format of choice for configuration files and is used by some exciting technologies like docker, Ansible, etc. It's great that VSTS now supports it as well. 

For this demo, we are creating build for a simple .Net Web Application. For the purpose of building our application, we need to do the following

1) Restore all NuGet packages

2) Build the entire solution

Our very simple yaml file looks as below

steps:

- task: nugetrestore@1

displayName: NuGet Restore

inputs:

projects: "MyWebApplication.sln"

- task: MSBuild@1

displayName: Building solution

inputs:

command: build

projects: "MyWebApplication.sln"

The file is pretty much self descriptive. As you can see we we have two tasks. The first task uses nugetrestore passing the solution as input. The second task executes MSBuild passing the applicatino's solution.

Commit the file to your local Git Repo and push to commit to TFS.

Creating the Build definition

Now that our yaml file is committed, we will create a build definition to use it. To do this, click on the New button to create build definition. For the build template, select YAML and click Apply

We will then be asked to provide the build name, agent queue and path to Yaml file. Make sure, you have selected the correct repository and branch in the "Get Sources" option for the build definition.

Please note that YAML builds are only supported for Git are not supported when TFVC is used a version control repository.

Click on the Triggers tab to make sure that Continuous Integration is selected as option

Click save to save your build. Now this build is set up as a continuous integration build for your repository and is triggered with every commit.

Conclusion:

If you compare the amount of work you had to do to create yaml build, it's really a breeze as compare to TFSBuilds. There are many use cases of using YAML for your build definitions. You can set up a complete pipeline, decoratively executing each steps which can be developed and tested locally before being used in VSTS.