.Net Core Buildpack

The .Net Core Paketo Buildpack supports building several configurations of .Net Core applications.

To build your app locally with the buildpack using the pack CLI, run

git clone https://github.com/paketo-buildpacks/samples
cd samples/dotnet-core/aspnet
pack build my-app --buildpack gcr.io/paketo-buildpacks/dotnet-core \
  --builder paketobuildpacks/builder:base
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See samples for how to run the app.

NOTE: Though the example above uses the Paketo Base builder, this buildpack is also compatible with the Paketo Full builder.

Supported Dependencies

The .Net Core Paketo Buildpack supports several versions of the .Net Core Framework. For more details on the specific versions supported in a given buildpack version, see the release notes.

Application Types

The .Net Core Buildpack supports several types of application source code that can be built into a container image. Developers can provide raw source code, or built artifacts like Framework-Dependent Deployments/Executables or Self-Contained Deployments when building their application.

Source Applications

The .Net Core Build Buildpack is capable of building application source code into Framework-Dependent Deployments (FDD) or Executables (FDE). This is achieved using the dotnet publish command. For .Net Core Framework 2.x applications, an FDD is produced as the default build artifact, while an FDE is produced when the application source is for .Net Core Framework 3.x.

Framework-Dependent Deployments or Framework-Dependent Executables

When building an application that has already been published as a Framework-Dependent Deployment or Framework-Dependent Executable, the buildpack will include the required .Net Core Framework dependencies and set the start command.

Self-Contained Deployment

When building an application as a Self-Contained Deployment(SCD), the buildpack will ensure the correct start command will be used to run your app. No .Net Core Framework dependencies will be included in the built image as they are already included in the SCD artifact.

Specifying Runtime and ASP.Net Versions

The .Net Core Runtime and .Net Core ASP.Net Buildpacks allow you to specify a version of the .Net Core Runtime and ASP.Net to use during deployment. This version can be specified in several ways including through a runtimeconfig.json, MSBuild Project file, or buildpack.yml file. When specifying a version of the .Net Core Runtime and ASP.Net, you must choose a version that is available within these buildpacks. These versions can be found in the .Net Core Runtime release notes and .Net Core ASP.Net release notes.

.Net Core ASP.Net will only be included in the build process if your application declares its Runtime Framework as either Microsoft.AspNetCore.App or Microsoft.AspNetCore.All.

Using buildpack.yml

To configure the buildpack to use .Net Core Runtime and ASP.Net v2.1.14 when deploying your app, include the values below in your buildpack.yml file:

---
dotnet-framework:
  version: "2.1.14"
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Note: If you include any dotnet-framework.version entry in your buildpack.yml, the buildpack will not run runtime version roll-forward logic. To learn more about roll-forward logic, see the Microsoft .Net Runtime documentation.

Using runtimeconfig.json

If you are using a runtimeconfig.json file, you can specify the .Net Core Runtime version within that file. To configure the buildpack to use .Net Core Runtime v2.1.14 when deploying your app, include the values below in your runtimeconfig.json file:

{
  "runtimeOptions": {
    "framework": {
      "version": "2.1.14"
    }
  }
}
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Using a Project file

If you are using a Project file (eg. *.csproj or *.fsproj), you can specify the .Net Core Runtime version within that file. To configure the buildpack to use .Net Core Runtime v2.1.14 when deploying your app, include the values below in your Project file:

<Project>
  <PropertyGroup>
    <RuntimeFrameworkVersion>2.1.14</RuntimeFrameworkVersion>
  </PropertyGroup>
</Project>
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Alternatively, for applications that do not rely upon a specific .Net Core Runtime patch version, you can specify the Target Framework and the buildpack will choose the appropriate .Net Core Runtime version. To configure the buildpack to use a .Net Core Runtime version in the 2.1 .Net Core Target Framework when deploying your app, include the values below in your Project file:

<Project>
  <PropertyGroup>
    <TargetFramework>netcoreapp2.1</TargetFramework>
  </PropertyGroup>
</Project>
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For more details about specifying a .Net Core version using a Project file, please review the Microsoft documentation.

.Net Core Framework Version Selection

The .Net Core Buildpack uses the same version selection policy that Microsoft has put together for .Net Core Framework. If you would like to know more about the policy please refer to this documentation provided by Microsoft.

Specifying an SDK Version

The .Net Core SDK Buildpack allows you to specify a version of the .Net Core SDK to use during deployment. This version is usually derived from the .Net Core Runtime version chosen for the application. The .Net Core SDK Buildpack maintains a set of SDK versions that are known compatible versions to run with any of the set of available .Net Core Runtime versions. When specifying a version of the .Net Core SDK, you must choose a version that is available within the buildpack. These versions can be found in the release notes.

However, the .Net Core SDK version can be explicitly set by specifying a version in either a buildpack.yml or global.json file.

Using buildpack.yml

To configure the buildpack to use .Net Core SDK v2.1.804 when deploying your app, include the values below in your buildpack.yml file:

---
dotnet-sdk:
  version: "2.1.804"
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Using global.json

If you are using a global.json file, you can specify the .Net Core SDK version within that file. To configure the buildpack to use .Net Core SDK v2.1.804 when deploying your app, include the values below in your global.json file:

{
  "sdk": {
    "version": "2.1.804"
  }
}
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Specifying a Custom Project Path

By default, the .Net Core Build Buildpack will consider the root directory of your codebase to be the project directory. This directory should contain a C#, F#, or Visual Basic Project file. If your project directory is not located at the root of your source code, you can override the project directory by including the following values in your buildpack.yml file:

---
dotnet-build:
  project-path: "src/asp_web_app"
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Buildpack-Set Environment Variables

DOTNET_ROOT

The DOTNET_ROOT environment variable specifies the path to the directory where .Net Runtimes and SDKs are installed.

• Set by: dotnet-core-runtime, dotnet-core-sdk, dotnet-core-aspnet buildpacks
• Phases: build and launch
• Value: path to the .Net root directory

RUNTIME_VERSION

The RUNTIME_VERSION environment variable specifies the version of the .Net Core Runtime installed by the .Net Core Runtime Buildpack.

• Set by: dotnet-core-runtime
• Phases: build
• Value: installed version of the .Net Core Runtime

SDK_LOCATION

The SDK_LOCATION environment variable specifies the file path location of the installed .Net Core SDK.

• Set by: dotnet-core-sdk
• Phases: build
• Value: path to the .Net Core SDK installation

PATH

The PATH environment variable is modified to enable the dotnet CLI to be found during subsequent build and launch phases.

• Set by: dotnet-core-sdk
• Phases: build and launch
• Value: path the directory containing the dotnet executable

Launch Process

The .Net Core Conf Buildpack will ensure that your application image is built with a valid launch process command. These commands differ slightly depending upon the type of built artifact produced during the build process.

For more information about which built artifact is produced for a Source Application, see this section.

Framework-Dependent Deployments and Source Applications

For Framework-Dependent Deployments (FDD), the dotnet CLI will be invoked to start your application. The application will be given configuration to help it bind to a port inside the container. The default port is 8080, but can be overridden using the $PORT environment variable.

dotnet myapp.dll --urls http://0.0.0.0:${PORT:-8080}
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Self-Contained Deployment and Framework-Dependent Executables

For Self-Contained Deployments and Framework-Dependent Executables, the executable will be invoked directly to start your application. The application will be given configuration to help it bind to a port inside the container. The default port is 8080, but can be overridden using the $PORT environment variable.

./myapp --urls http://0.0.0.0:${PORT:-8080}
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