This repository should not and cannot be a replacement for `referencesource`

[Kira-NT]

It's definitely nice to have this repo, but that doesn't mean we no longer need https://referencesource.microsoft.com/! Their existence is not mutually exclusive, as they serve quite different purposes.

First of all, as many folks have already pointed out, the code provided in this repository is incomplete, and some pretty important components (that have been available for inspection via Reference Source since forever) are missing.

Secondly, and arguably more importantly, Reference Source was designed for exploring the internals of the .NET Framework, so it was heavily optimized for searching specific symbols, their definitions, and their usage across the entire codebase in mere milliseconds. GitHub simply doesn't provide that functionality in any meaningful way.

For example, I'm currently working on a cross-framework .NET Standard 2.0 library that heavily relies on reflection. To make it compatible with .NET Framework, .NET Core, .NET, Mono (WineHQ), and Mono (Microsoft), I had to dig through a lot of source code related to all these platforms. The only thing that made this even remotely bearable was Reference Source. It allowed me to quickly find what I needed in the .NET Framework, compare it with the modern .NET (Core) codebase, and then work backwards from Microsoft's Mono to WineHQ's Mono implementation details. And now it's gone, making it nearly impossible to search for specific bits of code on GitHub. Tasks that used to take minutes or even seconds now take literal hours.

I honestly don't understand why Microsoft is eager to invest in costly "AI" infrastructure, yet when it comes to maintaining a small but incredibly useful web utility - oh boy, cuts and sacrifices must be made!

Anyways, until GitHub's "search for symbol" actually means that rather than "vaguely search for similar substrings across all available text in the repo and drop the results after N entries, so the user can't tell whether what they're looking for doesn't exist at all or just wasn't shown" - please, do keep Reference Source around. Thanks.

[odinserj]

I agree, https://referencesource.microsoft.com was providing invaluable help in understanding the internals of .NET Framework itself, and especially in comparison between its versions, and especially with the newer .NET platform when documentation doesn't cover some nuanced topics. Without this site, it's much more difficult to provide quality solutions that are aware of the changes for a framework with a long history. Such small tools might look not so important and niche-based, but they are of a great value, actually.

[aaron-chapman]

Yeah no doubt, this is an absolutely terrible replacement. It doesn't even compare in any meaningful way whatsoever, I was shocked to learn it's now gone. Just like everything else "good" in this world, they gotta go find some asinine 'reason' to go and break it!

[lloydjatkinson]

Did they decide to let AI make this decision? Because surely a human wouldn't make this absurdly ridiculous decision, right?

[IanKemp]

Honestly there's no good reason why MS didn't make ReferenceSource a view on top of their GitHub repos, literally years ago. All that's really needed is a layer to generate and cache ASTs from the GH source and bob's your auntie.

Anyways, until GitHub's "search for symbol" actually means that rather than "vaguely search for similar substrings across all available text in the repo and drop the results after N entries, so the user can't tell whether what they're looking for doesn't exist at all or just wasn't shown" - please, do keep Reference Source around. Thanks.

One would think that of all the things a Large Language Model would be good at, this is it. Yet instead we sit in 2025 with LLMs shoved into every place they are least useful, and ignored in the places where they'd make the most sense.

[R2D221]

@IanKemp:

a Large Language Model would be good at

I think using a LLM for this is overthinking it. The kind of analysis and symbol navigation that ReferenceSource used to do is perfectly done with the use of Roslyn (and probably that's what powered it).

I agree tho that the technology can be applied to any project, not just the .NET Framework.

[ber-sma]

I just found out, and am really disappointed, that we basically lost all power of referencesource. For years this has been the one invaluable source where search and navigation within the framework source was easy, especially symbolic search. Github is not an adequate replacement for that.

Please bring back referencesource.