.NET 6部署Azure App Service遇HTTP 500错误：路由优先级重复

问题背景 #

已将AngularJS应用迁移至.NET 6，功能运行正常，但每次通过Azure CI/CD Pipeline部署到Azure App Service时，都会出现HTTP 500错误，重启App Service后即可恢复正常。

异常详情 #

2022-07-26 18:43:18.397 +00:00 [Information] Microsoft.AspNetCore.Hosting.Diagnostics: Request starting HTTP/1.1 GET http://YOUR_WEBSITE_NAME.azurewebsites.net/ - -
2022-07-26 18:43:18.413 +00:00 [Error] Microsoft.AspNetCore.Diagnostics.ExceptionHandlerMiddleware: An unhandled exception has occurred while executing the request.
System.InvalidOperationException: Using ExpandEndpoint requires that the replaced endpoint have a unique priority. The following endpoints were found with the same priority:
/Index
/Index
/Index
   at Microsoft.AspNetCore.Routing.Matching.CandidateSet.ValidateUniqueScore(Int32 index)
   at Microsoft.AspNetCore.Routing.Matching.CandidateSet.ExpandEndpoint(Int32 index, IReadOnlyList`1 endpoints, IComparer`1 comparer)
   at Microsoft.AspNetCore.Mvc.RazorPages.Infrastructure.DynamicPageEndpointMatcherPolicy.ApplyAsync(HttpContext httpContext, CandidateSet candidates)
   at Microsoft.AspNetCore.Routing.Matching.DfaMatcher.SelectEndpointWithPoliciesAsync(HttpContext httpContext, IEndpointSelectorPolicy[] policies, CandidateSet candidateSet)
   at Microsoft.AspNetCore.Routing.EndpointRoutingMiddleware.<Invoke>g__AwaitMatch|8_1(EndpointRoutingMiddleware middleware, HttpContext httpContext, Task matchTask)
   at Microsoft.AspNetCore.Diagnostics.ExceptionHandlerMiddleware.<Invoke>g__Awaited|6_0(ExceptionHandlerMiddleware middleware, HttpContext context, Task task)

当前Startup.cs配置 #

public class Startup
{
    public Startup(IConfiguration configuration)
    {
        Configuration = configuration;
    }

    public IConfiguration Configuration { get; }

    // This method gets called by the runtime. Use this method to add services to the container.
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddRazorPages();
        services.AddMvc()
            .AddRazorPagesOptions(options =>
            {
                // Match all routes to the index so we can handle routing client-side.
                options.Conventions.AddPageRoute("/index", "{*url}");
            });
    }

    // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
    public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }
        else
        {
            app.UseExceptionHandler("/Error");
        }

        app.UseStaticFiles();

        app.UseRouting();
        

        app.UseEndpoints(endpoints =>
        {
            endpoints.MapRazorPages();
            endpoints.MapFallbackToPage("/Index");
   
        });

    }
}

问题原因 #

路由配置重复导致端点优先级冲突：

1. services.AddRazorPages() 自动注册了/Index页面的默认路由
2. options.Conventions.AddPageRoute("/index", "{*url}") 给/Index页面额外添加了通配符路由
3. endpoints.MapFallbackToPage("/Index") 又添加了一条fallback路由指向/Index

这三个配置生成了多个优先级相同的/Index端点，部署后路由匹配器无法区分，抛出异常；重启App Service时路由系统重新初始化，临时规避了冲突，但并未解决根本问题。

解决方案 #

简化路由配置，保留一种方式让所有请求指向/Index页面，避免重复注册：

方案一：移除冗余Mvc配置，保留Razor Pages和Fallback路由 #

修改ConfigureServices方法，去掉多余的AddMvc()配置（AddRazorPages()已包含必要的Mvc基础功能）：

public void ConfigureServices(IServiceCollection services)
{
    services.AddRazorPages();
}

Configure方法保留原有的MapRazorPages()和MapFallbackToPage("/Index")即可，fallback路由会将所有未匹配的请求导向Index页面，满足AngularJS客户端路由需求。

方案二：仅使用通配符路由，去掉Fallback配置 #

如果需要保留通配符路由，调整配置如下：

public void ConfigureServices(IServiceCollection services)
{
    services.AddRazorPages(options =>
    {
        options.Conventions.AddPageRoute("/Index", "{*url}");
    });
}

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    // 其他中间件配置不变

    app.UseEndpoints(endpoints =>
    {
        endpoints.MapRazorPages();
        // 移除 endpoints.MapFallbackToPage("/Index");
    });
}

通配符路由会让所有请求直接匹配到Index页面，无需额外fallback配置。

内容的提问来源于stack exchange，提问作者Ravi Mittal