Difference between .NET Core Runtime and SDK
💡 Concept Name
Runtime vs SDK in .NET Core
📘 Quick Intro
The .NET Core **Runtime** is needed to run apps, while the **SDK (Software Development Kit)** includes everything required to build and run applications—like the CLI, compilers, and libraries.
🧠 Analogy / Short Story
Think of the Runtime as a car engine that can **run** the car, while the SDK is like a full garage with **tools and parts** to build or modify the car. If you just want to drive, you only need the engine (runtime); to build or repair cars, you need the garage (SDK).
🔧 Technical Explanation
- Runtime: Includes only the libraries and components needed to **run** an app.
- SDK: Includes compilers (`csc`, `msbuild`), CLI tools, and the runtime itself.
dotnet runneeds SDK, butdotnet yourApp.dllneeds just Runtime.- Runtime is lightweight and meant for **deployment**, SDK is for **development**.
🎯 Purpose & Use Case
- ✅ Install SDK on developer machines to **create, compile, and test** code
- ✅ Install only Runtime on production servers to **run deployed apps**
- ✅ Helps minimize footprint and enhance performance during deployment
💻 Real Code Example
# On dev machine
dotnet new console
dotnet build
dotnet run
# On server (with runtime only)
dotnet MyApp.dll
❓ Interview Q&A
Q1: What is .NET Core Runtime?
A: A set of libraries and components required to run an application.
Q2: What is .NET Core SDK?
A: A development package that includes runtime + compilers + tools.
Q3: Do we need SDK to run apps?
A: No, Runtime is sufficient to run published apps.
Q4: Which one includes `dotnet new` and `dotnet build`?
A: The SDK.
Q5: Is SDK heavier than Runtime?
A: Yes, SDK includes more components for development.
Q6: Which should be installed on CI/CD pipelines?
A: SDK for build agents, Runtime for deployment machines.
Q7: Can SDK be used to run apps?
A: Yes, it includes runtime as well.
Q8: Is Runtime version-specific?
A: Yes, you must match the Runtime version your app targets.
Q9: How to check installed SDKs?
A: Run `dotnet --list-sdks` in the terminal.
Q10: Why separate SDK and Runtime?
A: To optimize deployment and reduce size on production environments.
📝 MCQs
Q1. Which of these is used to build .NET Core applications?
- Runtime
- CLI
- JRE
- SDK
Q2. Which tool does `dotnet build` require?
- Runtime
- MSIL
- SDK
- JDK
Q3. What does the .NET Core Runtime contain?
- All dev tools
- Only the components needed to run the app
- IDE support
- Compiler and debugger
Q4. Which one is lighter in size?
- SDK
- Runtime
- Both are equal
- Depends on OS
Q5. If you install SDK, do you get Runtime?
- No
- Yes
- Only partially
- Only in Visual Studio
Q6. Which command lists installed SDKs?
- dotnet check
- dotnet --version
- dotnet list
- dotnet --list-sdks
Q7. Which should be installed on production servers?
- SDK
- Runtime
- Visual Studio
- CLI only
Q8. Is SDK version always same as Runtime?
- Yes
- Not necessarily
- Always yes
- No relation
Q9. What is the purpose of SDK?
- Only to run apps
- To test in browser
- To develop, compile, and build applications
- To manage memory
Q10. Which tool allows you to use `dotnet new`?
- Runtime
- Compiler
- NuGet
- SDK
💡 Bonus Insight
Always install the **latest SDK** for development to ensure compatibility with new templates and APIs, but only deploy the Runtime version you’ve published against to reduce security surface and size.
📄 PDF Download
Need a handy summary for your notes? Download this topic as a PDF!