I notice that the file size of *.wasm compiled by Rust is acceptable . However , a minimal HelloWorld compiled by AspNet/Blazor will take up almost 2.8MB .
mono.wasm 1.75MB
mscorlib.dll 1.64MB
*.dll ....
If I understand correctly , the mono.wasm is the VM that runs in browser and runs the dll we write . Does that mean no matter what we do , we cannot make the size of files less than 1.75MB ? If not , is there a way to reduce the file size ?
Yes, 2.8 MBytes is quite a large payload for a 'Hello World' applications. However, Blazor is still very much an experimental technology, which is not ready for production use yet. There are numerous reasons why the generated output is so large at the moment:
Your current application runs in an interpreted mode, where the mono.wasm file ships the CLR to your browser, allowing it to execute your DLL. A faster, and more size efficient approach would be to use Ahead of Time Compilation (AOT) as described in this article. This would allow the compiler to strip out any library functions that are not used, giving a highly optimised output.
The features of the WebAssembly runtime itself are quite limited, future version will add garbage collection and various other capabilities that Blazor will be able to use directly. At the moment mono.wasm includes its own garbage collector.
The Blazor project itself has a number of open issues describing various optimisations which are being actively worked on. It already performs tree-shaking and various other optimisations, but this type of work takes time.