Swagger使用的时候报错：Failed to load API definition

NuGet添加Swashbuckle.AspNetCore，在Startup.cs添加和启用中间件Swagger

1public void ConfigureServices(IServiceCollection services)
2        {
3            #region Swagger
4            services.AddSwaggerGen(c =>
5            {
6                c.SwaggerDoc("v1", new Info
7                {
8                    Version = "v1.0.0",
9                    Title = "My Web API",
10                    Description = "说明文档",
11                    TermsOfService = "None",
12                    Contact = new Swashbuckle.AspNetCore.Swagger.Contact { Name = "My.Web", Email = "My.Web@xxx.com", Url = "https://www.cnblogs.com/Zev_Fung/" }
13                });
14            });
15            #endregion
16        }
17       
18        public void Configure(IApplicationBuilder app, IHostingEnvironment env)
19        {
20            #region Swagger
21            app.UseSwagger();
22            app.UseSwaggerUI(c =>
23            {
24                c.SwaggerEndpoint("/swagger/v1/swagger.json", "My Web API V1");
25            });
26            #endregion
27        }

使用自带的Kestrel web调试，输入地址：http://localhost:<port>/swagger，默认跳转到https://localhost:<port>/swagger/index.html

Swagger提示报错:

1Failed to load API definition.
2Errors
3Fetch errorInternal Server Error /swagger/v1/swagger.json

打开http://localhost:<port>/swagger/v1/swagger.json，提示错误

1An unhandled exception occurred while processing the request.
2NotSupportedException: Ambiguous HTTP method for action - xxxxx.Controllers.BooksController.Post (xxxxx). Actions require an explicit HttpMethod binding for Swagger 2.0
3Swashbuckle.AspNetCore.SwaggerGen.SwaggerGenerator.CreatePathItem(IEnumerable<ApiDescription> apiDescriptions, ISchemaRegistry schemaRegistry)
4
5Stack Query Cookies Headers
6NotSupportedException: Ambiguous HTTP method for action - xxxxx.Controllers.BooksController.Post (xxxxx). Actions require an explicit HttpMethod binding for Swagger 2.0
7Swashbuckle.AspNetCore.SwaggerGen.SwaggerGenerator.CreatePathItem(IEnumerable<ApiDescription> apiDescriptions, ISchemaRegistry schemaRegistry)
8System.Linq.Enumerable.ToDictionary<TSource, TKey, TElement>(IEnumerable<TSource> source, Func<TSource, TKey> keySelector, Func<TSource, TElement> elementSelector, IEqualityComparer<TKey> comparer)
9Swashbuckle.AspNetCore.SwaggerGen.SwaggerGenerator.CreatePathItems(IEnumerable<ApiDescription> apiDescriptions, ISchemaRegistry schemaRegistry)
10Swashbuckle.AspNetCore.SwaggerGen.SwaggerGenerator.GetSwagger(string documentName, string host, string basePath, string[] schemes)
11Swashbuckle.AspNetCore.Swagger.SwaggerMiddleware.Invoke(HttpContext httpContext, ISwaggerProvider swaggerProvider)
12Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)
13
14Show raw exception details

 或者在控制台查看输出错误

 大概意思是：不支持的异常:操作的HTTP方法不明确，方法需要必须指明请求方式

在方法加上 [HttpGet]、[HttpPost] 等，就可以通过 Swagger UI 查看 API

上面只是其中一种引起的Fetch errorInternal Server Error /swagger/v1/swagger.json原因，其他也是通过查看错误信息解决