How would you diagnose a thread pool starvation issue in a production ASP.NET Core application?

Thread pool starvation occurs when all available thread pool threads are busy (often due to blocking synchronous calls on async code, like .Result or .Wait()), causing queued work items to wait, visible via dotnet-counters' threadpool-queue-length metric climbing while threadpool-thread-count stays flat or grows slowly (since the pool only adds new threads gradually) -- diagnosed by capturing a trace or dump during the symptom window and looking for many threads blocked in synchronous wait states, then fixed by replacing blocking calls with proper async/await throughout the call chain.

// Common cause of starvation: blocking on async code
public IActionResult GetData() {
    var result = _service.GetDataAsync().Result;  // BLOCKS a thread pool thread
    return Ok(result);
}

// Fix: async all the way through
public async Task<IActionResult> GetData() {
    var result = await _service.GetDataAsync();
    return Ok(result);
}