Microsoft.AspNet.WebApi.Cors报错：请求资源不支持OPTIONS方法

Hey folks,

I’ve been wrestling with a persistent issue in my ASP.NET Web API project, and I’ve gone through tons of suggested fixes online—none of which have fully resolved the root problem. One workaround did get the system into a "functional" state, but it’s clearly just a band-aid rather than a real solution. Let me break down my setup and what I’ve tried so far:

• I’m building an ASP.NET Web API that’s intended to be hosted on IIS
• I’m using conventional routing exclusively, not attribute routing

• Verified the RouteConfig.cs setup to ensure default route templates (like api/{controller}/{id} with id marked optional) are correctly defined
• Checked IIS application pool settings: confirmed it’s running under a user with proper permissions to access project files and connected databases
• Tested routing behavior locally with IIS Express vs. full IIS to rule out environment-specific quirks
• Toggled the "Preload Enabled" setting in IIS to make sure the route table initializes properly on application startup
• Cleared IIS cache and recycled the application pool multiple times to eliminate stale configuration issues
• Enabled detailed routing diagnostics in the API to log incoming requests and route matching attempts—logs showed some requests were falling back to the default route unexpectedly, even when they should have matched a specific controller

I added a catch-all route (api/{*catchall}) at the end of my route configuration, which stopped 404 errors. But this doesn’t fix why the original conventional routes aren’t matching correctly—it just ensures every request gets routed somewhere, even if it’s not the intended controller.

I’m stuck figuring out why conventional routing isn’t behaving as expected in the IIS environment. Any insights or additional troubleshooting steps would be a huge help!

内容的提问来源于stack exchange，提问作者Ryan