The dotnet run command now supports directly executing single C# files, simplifying the process of running small programs or scripts. Previously, creating a project file was necessary, adding overhead for simple tasks. This streamlined approach allows developers to run dotnet run myapp.cs directly, handling compilation and execution in one step. The feature supports top-level statements, NuGet package dependencies declared within the file using #nullable directives, preprocessor directives, and more, providing a convenient and powerful way to execute C# code without project file management. This enhances the scripting capabilities of C# and makes it easier for quick prototyping and experimentation.
This Microsoft Developer Blog post announces a new feature in the .NET 8 SDK: the ability to directly execute a single C# file using the dotnet run command, without the need for explicit project files or compilation steps. Previously, running a C# application required creating a project file (like a .csproj) which contained information about the application, its dependencies, and build configurations. This new capability streamlines the process for simple scripts and exploratory programming, enabling developers to quickly run a C# file by simply typing dotnet run filename.cs.
The blog post explains that the dotnet run command now implicitly handles the necessary compilation steps behind the scenes. It automatically compiles the given .cs file into an assembly and then immediately executes it. This eliminates the need for manually compiling with dotnet build or creating a project file beforehand. This simplified workflow is particularly beneficial for beginners, educational scenarios, and quickly prototyping small programs where a full project structure is unnecessary overhead.
Furthermore, the post clarifies how this feature handles dependencies. While the implicit compilation works seamlessly for single-file programs, including multiple files requires explicitly passing them to the dotnet run command. For instance, dotnet run file1.cs file2.cs file3.cs would compile and run all three files together. This allows for slightly more complex scripts while still maintaining the simplified execution flow.
The blog post also highlights how external NuGet packages can be incorporated into these scripts. By using the #r directive within the C# file, similar to traditional C# scripting, developers can specify the NuGet packages they need. The dotnet run command will then automatically resolve and download these dependencies before compilation and execution. This allows for leveraging existing libraries and frameworks even within these simplified, project-less C# scripts.
Finally, the blog post emphasizes that this feature is primarily designed for scenarios where the simplicity and speed of directly executing a C# file outweigh the benefits of a full project structure. For larger, more complex applications, the traditional project-based approach with its explicit build configurations and dependency management remains recommended. This new dotnet run capability is positioned as a complementary tool for quickly prototyping, learning, and experimenting with C# code.
Summary of Comments ( 202 )
https://news.ycombinator.com/item?id=44122582
HN commenters generally express enthusiasm for
dotnet run app.cs, finding it a welcome simplification for running single-file C# programs. Several compare it favorably to similar functionality in other languages like Python, Ruby, and JavaScript, appreciating the reduced ceremony for quick scripts and experimentation. Some raise questions about how it handles dependencies and more complex projects, while others note potential implications for teaching and onboarding new C# developers. A few point out that this feature isn't entirely new, with similar results achievable through piping to the compiler, but acknowledge the improved developer experience this dedicated command offers. There's also discussion about compilation speed and whether pre-compilation might offer further performance improvements for repeated executions.The Hacker News post "Run a C# file directly using dotnet run app.cs" discussing the Microsoft blog post about the new
dotnet run app.csfeature has generated a fair number of comments, mostly revolving around comparisons to other languages and ecosystems, and reflecting on the convenience and implications of this new functionality.Several commenters draw parallels to similar features in other languages. One commenter points out the resemblance to running Python scripts directly using
python my_script.py, highlighting the streamlined experience this offers. Another commenter mentions similar functionality in PHP, emphasizing the ease of use for quick scripting tasks. The ability to execute single files without explicit compilation or project setup is a recurring theme, with several comments praising the reduced friction for beginners and small projects.A few comments delve into the potential implications for tooling and development workflows. One user speculates about the impact on IDEs and how they might integrate this feature, suggesting a more dynamic development process. Another discusses the possibility of using this feature for scripting within larger .NET projects, foreseeing benefits in automation and build processes.
The discussion also touches on the performance aspects of this feature. A commenter raises the question of whether
dotnet run app.csincurs additional overhead compared to running a pre-compiled executable. This prompts a discussion about the potential for behind-the-scenes caching mechanisms and the trade-offs between ease of use and execution speed.Some commenters express concern about the potential for misuse or confusion, particularly among newcomers to C#. They worry that this simplified approach might encourage bad practices or obscure the underlying compilation process. However, others counter this argument by emphasizing the value of lowering the barrier to entry for beginners and promoting experimentation.
Finally, a few commenters offer suggestions for further improvements and extensions to the feature. One suggests the ability to specify command-line arguments directly to the script. Another proposes integrating this functionality with other .NET tools and frameworks. Overall, the comments reflect a generally positive reception to the
dotnet run app.csfeature, with many acknowledging its potential to simplify C# development and expand its use cases.