ASP.NET 3.1 Web API模板无法与Postman连接求助

Hey there! I totally get how frustrating it is when your API runs fine in the terminal but won't play nice with Postman. Let's walk through the most common fixes to get you connected:

1. Double-Check the API's Running Address & Port #

• When you run dotnet run, your CMD should output lines like Now listening on: https://localhost:5001 and Now listening on: http://localhost:5000. Make sure Postman is using the exact same address (including HTTP/HTTPS and port number) for your requests. For example, the default template's test endpoint is https://localhost:5001/weatherforecast.
• If you can't see the full address in the terminal, open your project's launchSettings.json file (under the Properties folder) and look for the applicationUrl field—this lists all the URLs your API is listening on.

2. Fix HTTPS Certificate Trust Issues #

• ASP.NET Core uses HTTPS by default, and Windows might not trust the local development certificate automatically. Try accessing the API via HTTP first (e.g., http://localhost:5000/weatherforecast) in Postman—if that works, the problem is with the HTTPS certificate.
• To trust the certificate, run this command in CMD:

  dotnet dev-certs https --trust
  

  Follow the on-screen prompts to confirm trust, then restart your API and try Postman again with the HTTPS address.

3. Verify the API is Actually Accessible #

• Open Chrome and paste the API's endpoint URL directly (e.g., https://localhost:5001/weatherforecast). If you see the expected JSON response, the API is working correctly, and the issue lies with Postman's configuration.
• If Chrome can't access it either, your port might be occupied. Try running the API on a different port with this command:

  dotnet run --urls "http://localhost:5002;https://localhost:5003"
  

  Then update Postman to use the new port.

4. Audit Postman's Request Settings #

• Ensure you're using the correct HTTP method: the default WeatherForecast endpoint uses GET, so don't accidentally select POST/PUT/DELETE.
• Remove any unnecessary headers or parameters from your request—this template doesn't require extra authentication or custom headers out of the box.
• If you use a system proxy, Postman might route local requests through it. Go to Postman's Settings > Proxy, disable "Use system proxy", or add localhost to the "No proxy for" list.

5. Rule Out Firewall/Antivirus Interference #

• Windows Firewall or third-party antivirus software might block local API connections. Temporarily disable them (carefully!) and test the connection in Postman. If it works, add your API's port to the firewall's allowed applications list.

If none of these steps resolve the issue, share the exact error message from Postman and the full output from your dotnet run command—those details will help narrow down the problem further!

内容的提问来源于stack exchange，提问作者Jaifran Hernández