Quickstart: Create a build validation GitHub workflow

2022-10-07

In this quickstart, you will learn how to create a GitHub workflow to validate the compilation of your .NET source code in GitHub. Compiling your .NET code is one of the most basic validation steps that you can take to help ensure the quality of updates to your code. If code doesn't compile (or build), it's an easy deterrent and should be a clear sign that the code needs to be fixed.

Prerequisites

A GitHub account.
A .NET source code repository.

Create a workflow file

In the GitHub repository, add a new YAML file to the .github/workflows directory. Choose a meaningful file name, something that will clearly indicate what the workflow is intended to do. For more information, see Workflow file.

Important

GitHub requires that workflow composition files to be placed within the .github/workflows directory.

Workflow files typically define a composition of one or more GitHub Action via the jobs.<job_id>/steps[*]. For more information, see, Workflow syntax for GitHub Actions.

Create a new file named build-validation.yml, copy and paste the following YML contents into it:

name: build

on:
  push:
  pull_request:
    branches: [ main ]
    paths:
    - '**.cs'
    - '**.csproj'

env:
  DOTNET_VERSION: '6.0.401' # The .NET SDK version to use

jobs:
  build:

    name: build-${{matrix.os}}
    runs-on: ${{ matrix.os }}
    strategy:
      matrix:
        os: [ubuntu-latest, windows-latest, macOS-latest]

    steps:
    - uses: actions/checkout@v3
    - name: Setup .NET Core
      uses: actions/setup-dotnet@v3
      with:
        dotnet-version: ${{ env.DOTNET_VERSION }}

    - name: Install dependencies
      run: dotnet restore
      
    - name: Build
      run: dotnet build --configuration Release --no-restore

In the preceding workflow composition:

The name: build defines the name, "build" will appear in workflow status badges.
```
name: build
```
The on node signifies the events that trigger the workflow:
```
on:
  push:
  pull_request:
    branches: [ main ]
    paths:
    - '**.cs'
    - '**.csproj'
```
- Triggered when a push or pull_request occurs on the main branch where any files changed ending with the .cs or .csproj file extensions.
The env node defines named environment variables (env var).
```
env:
  DOTNET_VERSION: '6.0.401' # The .NET SDK version to use
```
- The environment variable DOTNET_VERSION is assigned the value '6.0.401'. The environment variable is later referenced to specify the dotnet-version of the actions/setup-dotnet@v3 GitHub Action.
The jobs node builds out the steps for the workflow to take.
```
jobs:
  build:

    name: build-${{matrix.os}}
    runs-on: ${{ matrix.os }}
    strategy:
      matrix:
        os: [ubuntu-latest, windows-latest, macOS-latest]

    steps:
    - uses: actions/checkout@v3
    - name: Setup .NET Core
      uses: actions/setup-dotnet@v3
      with:
        dotnet-version: ${{ env.DOTNET_VERSION }}

    - name: Install dependencies
      run: dotnet restore
      
    - name: Build
      run: dotnet build --configuration Release --no-restore
```
- There is a single job, named build-<os> where the <os> is the operating system name from the strategy/matrix. The name and runs-on elements are dynamic for each value in the matrix/os. This will run on the latest versions of Ubuntu, Windows, and macOS.
- The actions/setup-dotnet@v3 GitHub Action is required to set up the .NET SDK with the specified version from the DOTNET_VERSION environment variable.
- (Optionally) Additional steps may be required, depending on your .NET workload. They're omitted from this example, but you may need additional tools installed to build your apps.
  - For example, when building an ASP.NET Core Blazor WebAssembly application with Ahead-of-Time (AoT) compilation you'd install the corresponding workload before running restore/build/publish operations.
```
- name: Install WASM Tools Workload
  run: dotnet workload install wasm-tools
```
  For more information on .NET workloads, see dotnet workload install.
- The dotnet restore command is called.
- The dotnet build command is called.

In this case, think of a workflow file as a composition that represents the various steps to build an application. Many .NET CLI commands are available, most of which could be used in the context of a GitHub Action.

Create a workflow status badge

It's common nomenclature for GitHub repositories to have a README.md file at the root of the repository directory. Likewise, it's nice to report the latest status for various workflows. All workflows can generate a status badge, which are visually appealing within the README.md file. To add the workflow status badge:

From the GitHub repository select the Actions navigation option.
All repository workflows are displayed on the left-side, select the desired workflow and the ellipsis (...) button.
- The ellipsis (...) button expands the menu options for the selected workflow.
Select the Create status badge menu option.
Select the Copy status badge Markdown button.
Paste the Markdown into the README.md file, save the file, commit and push the changes.