Fifteen years ago, Microsoft created C# as part of its .NET initiative. It’s built into Visual Studio, the company’s Integrated Development Environment (IDE), and used to develop programs for Windows (in addition to a host of websites and applications). Its popularity is unquestionable—but is that popularity starting to wane? In a posting that recently attracted some buzz online, .NET developer Justin Angel argued that the .NET ecosystem is headed for collapse—and that could take interest in C# along with it. “The Microsoft developer ecosystem is experiencing plummeting employment opportunities and declining community interest,” he wrote. “Sure, you’ll always be able to find a job working in C# (like you would with COBOL), but you’ll miss out on customer reach and risk falling behind the technology curve.” Angel claims he pulled data from Indeed.com that shows job trends for C# on the decline. Data from the TIOBE developer interest index mirrors that trend, he said, with “C# developer interest down approximately 60% down back to 2006-2008 levels.” Based on that data and the suggested downward trend, Angel concludes that the reach of Microsoft’s developer ecosystem has eroded “due to the rise of non-Microsoft Web frameworks and mobile platforms” such as iOS and Android. Microsoft’s own habit of rolling out new technologies, he added, has also cooled developer interest in those platforms—anybody who invested massive amounts of time in learning Silverlight, for example, probably grew frustrated when Microsoft largely abandoned that framework in favor of Universal apps. Angel being a former program manager for Silverlight just makes the posting more interesting—this is clearly someone who believed enough in Microsoft’s ecosystem and strategy to work for the company. Now he’s learning Java and poring through the Android source code. But is C# really on the decline? Not at the moment: According to Dice’s data, the popularity of C# has risen over the past several years; it ranks No. 26 on Dice’s ranking of most-searched terms. Meanwhile, ".NET" ranks No. 7 among most-searched terms on Dice, followed by “.NET developer” at No. 10 (searches without a location filter). As Angel stated in his posting, C# and the .NET ecosystem aren’t going anywhere soon: Despite Microsoft’s weak position in mobile, Windows continues to dominate the traditional PC arena. And certainly employers still seem very interested in hiring people with the right combination of skills for that ecosystem. But any signs of long-term instability are worth keeping an eye on.