YAML Templates

Azure DevOps pipelines use YAML to define build and release workflows in a human- and machine-readable format. In this guide, we'll explore YAML essentials, step through an ASP.NET pipeline example, and demonstrate how to leverage templates for reusable CI/CD components.

Example: ASP.NET CI/CD Pipeline

Use the following ASP.NET pipeline to build, test, and package your web application. For full task details, see the Azure DevOps ASP.NET docs.

trigger:
  - master

pool:
  vmImage: 'windows-latest'
  name: 'Default'

variables:
  solution: '**/*.sln'
  buildPlatform: 'Any CPU'
  buildConfiguration: 'Release'

steps:
  - task: NuGetToolInstaller@1

  - task: NuGetCommand@2
    inputs:
      restoreSolution: '$(solution)'

  - task: VSBuild@1
    inputs:
      solution: '$(solution)'
      msbuildArgs: >-
        /p:DeployOnBuild=true
        /p:WebPublishMethod=Package
        /p:PackageAsSingleFile=true
        /p:SkipInvalidConfigurations=true
        /p:PackageLocation="$(build.artifactStagingDirectory)\$(Build.BuildId).zip"
      platform: '$(buildPlatform)'
      configuration: '$(buildConfiguration)'

  - task: VSTest@2
    inputs:
      platform: '$(buildPlatform)'
      configuration: '$(buildConfiguration)'

Starter Pipeline

Begin with a minimal YAML pipeline and customize it for your project:

trigger:
  - master

pool:
  vmImage: 'ubuntu-latest'
  name: 'Default'

steps:
  - script: echo Hello, world!
    displayName: 'Run a one-line script'

  - script: |
      echo Add other tasks to build, test, and deploy your project.
      echo See https://aka.ms/yaml
    displayName: 'Run a multi-line script'

Key elements:

• trigger: Events that kick off the pipeline.
• pool: Agent selection (e.g., ubuntu-latest).
• steps: Tasks or scripts to execute in sequence.

Viewing a Pipeline Run

A typical Azure DevOps pipeline run reveals build warnings, repository info, branch, and elapsed time:

Creating a New Pipeline

When you create a pipeline, select your source—Azure Repos Git, Bitbucket Cloud, GitHub, or GitHub Enterprise—and choose the Starter Pipeline for IntelliSense support:

The default YAML appears:

trigger:
  - master

pool:
  vmImage: 'ubuntu-latest'
  name: 'Default'

steps:
  - script: echo Hello, world!
    displayName: 'Run a one-line script'
  - script: |
      echo Add other tasks to build, test, and deploy your project.
      echo See https://aka.ms/yaml
    displayName: 'Run a multi-line script'

Validate and run to see output:

Starting: Run a one-line script
> echo Hello, world!
  Hello, world!

YAML Structure Basics

YAML relies on three core constructs: key–value pairs, lists, and nested mappings. Use indentation for hierarchy and avoid tabs.

Examples:

Key–value pair:

trigger:
  - master

List:

fruits:
  - Apple
  - Banana
  - Cherry

Nested mapping:

pool:
  vmImage: ubuntu-latest
  name: Default

Variables and Overrides

Define pipeline variables at the top and allow runtime overrides:

variables:
  solution: '**/*.sln'
  buildPlatform: 'Any CPU'
  buildConfiguration: 'Release'
  pipelineRunnerName: 'DefaultUser'
  pipelineRunnerAge: 30

steps:
  - script: echo Hello, $(pipelineRunnerName)!
    displayName: 'Greet runner'
  - script: echo Runner age is $(pipelineRunnerAge)
    displayName: 'Show runner age'

Best Practices

• Leverage comments to clarify intent.
• Keep pipelines DRY by defining reusable variables and templates.
• Organize common logic into separate files.

Applying Templates

Break out common steps into parameterized or extendable templates.

Example templates:

nuget.yml

steps:
  - task: NuGetToolInstaller@1
  - task: NuGetCommand@2
    inputs:
      command: 'restore'
      restoreSolution: '$(solution)'

build.yml

steps:
  - task: VSBuild@1
    inputs:
      solution: '$(solution)'
      msbuildArgs: >-
        /p:DeployOnBuild=true
        /p:WebPublishMethod=Package
        /p:PackageAsSingleFile=true
        /p:SkipInvalidConfigurations=true
        /p:PackageLocation="$(build.artifactStagingDirectory)"
      platform: '$(buildPlatform)'
      configuration: '$(buildConfiguration)'

test.yml

steps:
  - task: VSTest@2
    inputs:
      platform: '$(buildPlatform)'
      configuration: '$(buildConfiguration)'

Reference templates in your main pipeline (azure-pipelines.yml):

trigger:
  - master

pool:
  vmImage: 'ubuntu-latest'
  name: 'Default'

variables:
  solution: '**/*.sln'
  buildPlatform: 'Any CPU'
  buildConfiguration: 'Release'
  pipelineRunnerName: 'DefaultUser'
  pipelineRunnerAge: 30

steps:
  - script: echo Hello, $(pipelineRunnerName)!
    displayName: 'Greet runner'

  - template: 'nuget.yml'
  - template: 'build.yml'
  - template: 'test.yml'

Build and Test Summaries

After applying templates, review your build results in the pipeline summary:

Monitor recent runs and their status:

Check detailed logs to confirm test success:

Conclusion

Azure DevOps YAML templates enable modular, maintainable CI/CD pipelines. You’ve learned:

• Core YAML syntax and structure
• Defining variables and overrides
• Extracting and reusing templates
• Reviewing build and test outcomes

Experiment with these patterns to streamline your Azure DevOps workflows.

Links and References

• Azure DevOps Pipelines
• YAML Official Site
• Azure DevOps ASP.NET Pipeline Docs
• Azure Pipelines YAML Schema