ASP.NET 4.5应用中Swagger UI访问跳转登录页的问题求助

Hey there! Let's break down why your Swagger UI is redirecting to the login page and how to fix it. I’ve dealt with this exact issue a few times with ASP.NET 4.5 Web API and Swashbuckle, so here’s what to check step by step:

The most common culprit is a global authorization rule that blocks anonymous access to all paths—including Swagger.

Open your Web.config and look for a section like this:

<system.web>
  <authorization>
    <deny users="?" /> <!-- This blocks all unauthenticated users -->
  </authorization>
</system.web>

If that exists, add location-specific rules to allow anonymous access to Swagger paths:

<!-- Allow unauthenticated access to Swagger root -->
<location path="swagger">
  <system.web>
    <authorization>
      <allow users="*" />
    </authorization>
  </system.web>
</location>

<!-- Allow unauthenticated access to Swagger UI -->
<location path="swagger/ui">
  <system.web>
    <authorization>
      <allow users="*" />
    </authorization>
  </system.web>
</location>

If you added a global AuthorizeAttribute to your Web API, it might be intercepting Swagger requests too.

Check your WebApiConfig.cs or SwaggerConfig.cs for a line like:

GlobalConfiguration.Configuration.Filters.Add(new AuthorizeAttribute());

If so, replace it with a custom authorization filter that skips Swagger paths:

public class SkipSwaggerAuthorizeAttribute : AuthorizeAttribute
{
    public override void OnAuthorization(HttpActionContext actionContext)
    {
        var requestPath = actionContext.Request.RequestUri.PathAndQuery;
        // Bypass authorization for all Swagger-related endpoints
        if (requestPath.StartsWith("/swagger", StringComparison.OrdinalIgnoreCase))
        {
            return;
        }
        base.OnAuthorization(actionContext);
    }
}

Then update the global filter to use your custom attribute:

GlobalConfiguration.Configuration.Filters.Add(new SkipSwaggerAuthorizeAttribute());

If you’re using IIS, make sure no URL rewrite rules are accidentally redirecting Swagger requests to the login page. Look in Web.config for a <rewrite> section and verify none of the rules target /swagger or /swagger/ui.

While less likely, double-check your AngularJS 1.5.4 routing config to ensure there’s no route that matches /swagger and redirects to login. Test accessing the full Swagger UI URL directly: localhost:9000/swagger/ui/index—if it still redirects, the issue is definitely on the backend.

Old versions of Swashbuckle can have compatibility issues with ASP.NET 4.5 Web API. Ensure you’re using a version that supports .NET 4.5 (typically Swashbuckle.Core 5.x series). If needed, update the NuGet package:

Update-Package Swashbuckle.Core

If none of these fix the issue, sharing these details will help narrow it down:

• Snippets of your Web.config (authorization/authentication sections)
• Full code from SwaggerConfig.cs
• Any custom authentication/authorization frameworks you’re using (e.g., ASP.NET Identity, OAuth2)
• Which component is triggering the login redirect (Forms Auth, custom filter, etc.)

内容的提问来源于stack exchange，提问作者Nathan Pena