Using counters in Azure DevOps pipeline to increment assembly version numbers
Tags: azure, pipeline, devops, counter
Published: 2021-12-10 15:13:57

There are [many pipeline task extensions](https://marketplace.visualstudio.com/search?term=versioning&target=AzureDevOps&category=All%20categories&sortBy=Relevance) in the Azure Marketplace which can be installed directly to your DevOps instance. But for funny 😁 reasons, I want to do this myself where I ended up using the counter function and found it satisfied.

I hope you also will find this helpful 🎉🎉🎉.

[Counter](https://docs.microsoft.com/en-us/azure/devops/pipelines/process/expressions?view=azure-devops#counter) function maintains a seed value that should be variable in your pipeline and will increment it on each pipeline run.

So, here is my complete pipeline yml file before going further,

```
name: '$(Build.DefinitionName)_$(SourceBranchName)_$(Year:yyyy).$(Month).$(DayOfMonth).$(revision)'

trigger:
    branches:
        include:
            - master
            - develop    

pool:
  vmImage: 'windows-latest'

variables:
  solution: '*/.sln'
  buildPlatform: 'Any CPU'
  buildConfiguration: 'Release'  
  buildNumber: 'Will be set dynamically'
  revision: $[counter(format('{0:dd}', pipeline.startTime), 1)]

steps:
- task: PowerShell@2
  displayName: 'Preparing Build Number'
  inputs:
    targetType: 'inline'
    script: |
      $currentDate = $(Get-Date)
      $year = $currentDate.Year
      $month = $currentDate.Month
      $day = $currentDate.Day
      Write-Host $currentDate
      Write-Host $day
      Write-Host $env:revision
      Write-Host "##vso[task.setvariable variable=buildNumber]$year.$month.$day.$env:revision"

- task: UseDotNet@2
  displayName: 'Use .NET 6'
  inputs:
    packageType: 'sdk'
    version: '6.0.x'
    includePreviewVersions: true

- task: NuGetToolInstaller@1
  displayName: 'Update Nuget'
  inputs:
    checkLatest: true

- task: NuGetCommand@2
  displayName: 'NuGet restore'
  inputs:
    command: 'restore'
    restoreSolution: '$(solution)'
    feedsToUse: config
    nugetConfigPath: nuget.config

- task: DotNetCoreCLI@2
  displayName: Build
  inputs:
    projects: 'ProjectName.csproj'
    arguments: '--configuration $(buildConfiguration) /p:AssemblyVersion=$(buildNumber)'

- task: DotNetCoreCLI@2
  displayName: Publish
  inputs:
    command: publish
    publishWebProjects: false
    projects: 'ProjectName.csproj'
    arguments: '--configuration $(BuildConfiguration) --output $(build.artifactstagingdirectory) /p:Version=$(buildNumber)'
    zipAfterPublish: True

- task: PublishBuildArtifacts@1
  displayName: 'Publish Artifact'
  inputs:
    PathtoPublish: '$(build.artifactstagingdirectory)'
  condition: succeededOrFailed()
```

We will focus only on the `variables section` and the `PowerShell task` in this blog.

In the `variables section`, I have added a variable `revision` that is set from the counter function.

```revision: $[counter(format('{0:dd}', pipeline.startTime), 1)]```

This counter function is using `startTime` of the pipeline in the format of day number as its seed. The counter starts from 1.

On each pipeline run, the counter will check for changes in the day number in the pipeline.startTime, and if it's new, the counter will reset to the default value which is 1. 

As of now, we have achieved a revision number that gets incremented on each pipeline run on the same day and also resets to 1 on the next day.

Now, in the `PowerShell task`, we are going to use this revision to form a build number for our assembly.

```Write-Host "##vso[task.setvariable variable=buildNumber]$year.$month.$day.$env:revision"```

We are trying to achieve a build number in this format - `yyyy.mm.dd.revision` => `2021.12.26.13`

In the above Write-Host command, we are not printing any values to the output console, instead, we are using the [logging command #vso to set the variable](https://docs.microsoft.com/en-us/azure/devops/pipelines/scripts/logging-commands?view=azure-devops&tabs=bash#setvariable-initialize-or-modify-the-value-of-a-variable) `buildNumber` with our required value.

Finally, in the `build` and `publish` tasks, I passed the `buildNumber` to the `/p:AssemblyVersion` and `/p:Version` properties respectively.

You can write your own logic to set the `buildNumber` using the counter function and achieve build numbers in any format you want.

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