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Detection

migetpacks detects a .NET application when any of the following are present:
  • *.sln or *.slnx (solution files, root level)
  • global.json (root level)
  • *.csproj, *.fsproj, or *.vbproj (project files, up to 2 levels deep)

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Version Detection

.NET SDK version is resolved in the following priority order:
SourceExample
global.json (sdk.version){"sdk": {"version": "8.0.100"}}
*.csproj (TargetFramework)<TargetFramework>net8.0</TargetFramework>
Default8.0
The TargetFramework value has the net prefix stripped (e.g., net8.0 becomes 8.0).

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Build Process

migetpacks generates a multi-stage Dockerfile using the official .NET SDK and ASP.NET runtime images: 
# Build stage
FROM mcr.microsoft.com/dotnet/sdk:8.0 AS builder
WORKDIR /build

# .NET build optimizations
ENV NUGET_XMLDOC_MODE=skip
ENV DOTNET_SKIP_FIRST_TIME_EXPERIENCE=1
ENV DOTNET_CLI_TELEMETRY_OPTOUT=1
ENV DOTNET_NOLOGO=1

# Copy source code
COPY . .

# Restore, build, and publish
RUN dotnet restore \
    && dotnet publish --configuration Release --no-restore -p:PublishDir=bin/publish

# Runtime stage
FROM mcr.microsoft.com/dotnet/aspnet:8.0
WORKDIR /app
COPY --from=builder --chown=1000:1000 /build /app

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Source Code Cleanup

Since .NET is a compiled language, source code is completely removed from the runtime image after publishing:
RemovedReason
*.cs, *.fs, *.vbSource files (compiled to DLLs)
*.csproj, *.fsproj, *.vbprojProject files
*.sln, *.slnxSolution files
obj/Intermediate build files
bin/Release/net*/, bin/Debug/Non-publish build output
Only the bin/publish/ directory contents are kept in the final image.

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.NET Tool Restore

If a .config/dotnet-tools.json is present, dotnet tool restore is run before the build to install any required .NET CLI tools.

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Run Command

The default run command for .NET applications: 
dotnet MyApp.dll
migetpacks detects the main DLL from the publish output. Override with RUN_COMMAND or a Procfile: 
web: dotnet MyApp.dll --urls http://0.0.0.0:5000

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Runtime Configuration

The following environment variables are set for production:
VariableValue
ASPNETCORE_ENVIRONMENTProduction
DOTNET_RUNNING_IN_CONTAINERtrue
DOTNET_SYSTEM_GLOBALIZATION_INVARIANT1
DOTNET_CLI_TELEMETRY_OPTOUT1
ASPNETCORE_HTTP_PORTS5000

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Caching

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Layer Caching

The .NET build uses NuGet cache mounts for dependency caching:
ScenarioDependency Restore
First buildRuns
Source code change onlyNuGet packages cached via mount
Project file changeRuns restore

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BUILD_CACHE_DIR

When BUILD_CACHE_DIR is set, NuGet packages are cached via BuildKit mount at:
Cache PathContents
NuGet packages mount~/.nuget/packages

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DHI Support

Docker Hardened Images are supported for .NET builds.
StageImage
Builddhi.io/dotnet:{version}-sdk
Runtimedhi.io/aspnetcore:{version}

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DHI Notes

  • Build SDK images include the full .NET SDK for compilation.
  • Runtime images are based on ASP.NET Core distroless images (no shell, no apt-get).
  • The nonroot user is used instead of the miget user.
  • Suitable for web APIs and ASP.NET Core applications.

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Example with DHI

docker run --rm \
  -v /path/to/dotnet-app:/workspace/source \
  -v /var/run/docker.sock:/var/run/docker.sock \
  -e OUTPUT_IMAGE=my-dotnet-app:latest \
  -e USE_DHI=true \
  miget/migetpacks:latest

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Example

docker run --rm \
  -v /path/to/dotnet-app:/workspace/source \
  -v /var/run/docker.sock:/var/run/docker.sock \
  -e OUTPUT_IMAGE=my-dotnet-app:latest \
  miget/migetpacks:latest

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Monorepo with PROJECT_PATH

docker run --rm \
  -v /path/to/monorepo:/workspace/source \
  -v /var/run/docker.sock:/var/run/docker.sock \
  -e OUTPUT_IMAGE=my-api:latest \
  -e PROJECT_PATH=src/MyApi \
  miget/migetpacks:latest

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With custom build command

docker run --rm \
  -v /path/to/dotnet-app:/workspace/source \
  -v /var/run/docker.sock:/var/run/docker.sock \
  -e OUTPUT_IMAGE=my-dotnet-app:latest \
  -e BUILD_COMMAND="dotnet publish -c Release -o /build/out" \
  miget/migetpacks:latest