It's a curious thing, the .NET ecosystem. The overwhelming majority of it's ecosystem seems to be dominated by Microsoft first-party libraries and frameworks. 3rd party libraries and frameworks seem to either get swallowed up by Microsoft, killed, or never reach critical-mass.

Often in the .NET ecosystem, it seems there is exactly one library or framework for thing $X or $Y. Whereas in the JVM ecosystem, you have 30+ logging libraries, 87 different MVC frameworks, etc. (yes, I'm being a bit facetious, but you get the point).

I imagine .NET developers often think this is a good thing, in regard to their ecosystem. No guessing what to use, just go with the "blessed" path and don't think about it. And, to that end, there is some obvious merit to this.

However, I feel the .NET ecosystem loses out on cross-pollination of ideas. There's zero possibility Microsoft's employees just happen to make the best frameworks and libraries... there should be many web frameworks - each competing for mindshare and trying to out-innovate each other, each with their own pro's and con's, etc.

So, while .NET might be technically open source, it still feels rather like a closed source ecosystem, controlled by a single corporate entity.