👋 Introduction

When I started to using command lines wherever its possible on my journey of software, I got striked that one of my understanding is wrong about .NET Environments and Build Configuration. When try to go one step ahead on my way of working, it is leading to learn deeply. By this way only I got clarified about .NET Environment and Build Configuration.

🕵️ Initial My Understanding about dotnet build command: What I expected

When I executed the dotnet build command and saw all my DLL files move into the bin/Debug/net8.0/ folder, I felt confident. In my mind, because the build was successful and located in the "Debug" directory, the application was "marked" as a development version.

I expected that when I executed the DLL directly from that folder, the application would automatically realize it was in Development mode. I assumed it would naturally pick up my configuration.Development.json and start writing logs to the console as I had configured. To me, "Debug Build" and "Development Environment" were the same thing, if the files were in the Debug folder, the app should act like it’s in development.

🧩 Final understanding about Build configuration and environment

As I moved further into my command-line journey, I learned that these two concepts are actually decoupled. I found that the Build Configuration (Debug or Release) only decides how the code is compiled and where it is stored. It does not control the Hosting Environment.

The "striking" realization was that when we run a .NET application via the command line, it doesn't care about which folder the DLL is sitting in. Instead, the runtime looks for an environment variable called ASPNETCORE_ENVIRONMENT. If we don't explicitly set this variable to "Development," .NET defaults to its "Production" mode for safety.

I finally understood that my IDE (Visual Studio) was doing a lot of "magic" for me behind the scenes using launchSettings.json. Once I stepped out into the command line, I realized I had to manually tell the runtime which environment to use. Now, I know that even a Debug build can run in a "Production" state if the environment variables aren't handled correctly.

🔍 The Bridge Between Build and Run

To summarize the deep learning I gained, we must look at these two distinct stages:

• Build Time (-c Debug/Release): This happens when you run dotnet build. It determines if your code is optimized for performance (Release) or includes extra info for debugging (Debug). It simply places the files in a folder.

• Run Time (ASPNETCORE_ENVIRONMENT): This happens the moment you start the DLL. The application ignores the folder name and looks at the OS environment variables. If you don't tell it otherwise, it assumes it is in Production to keep things secure.

If you are working on Ubuntu or any command line, you can bridge this gap by setting the environment manually before running your app:

• Command: export ASPNETCORE_ENVIRONMENT=Development

• Then run: dotnet bin/Debug/net8.0/Project.dll

👋 Conclusion: My Journey to Deeper Understanding

Stepping away from the "magic" of the Visual Studio "Play" button was a challenge, but it was the best way to truly see how .NET works under the hood. By choosing to use the command line, I was forced to face the gap between my expectations and the actual behavior of the framework.

This journey taught me that in software, things are often more decoupled than they appear. A folder name like /Debug is just a location, not a command to the runtime. I am glad I took this "one step ahead" in my way of working, as it turned a simple build error into a fundamental understanding of .NET architecture.

If you are also moving from IDEs to the CLI, remember: don't just trust the folder path—always check your environment variables!

Happy Coding!! ☕.