可选参数在Swashbuckle中导致null异常。Asp.Netpore

问题描述：

我有一个asp.net core 2.0 api控制器动作，带有一个可选（和可为空）参数。 Swashbuckle.AspNetCore 1.0.0当方法签名中存在此参数时，生成Swagger文档失败，但如果将其从签名中删除，则会成功。它出现的可选参数是错误的原因，但我不知道为什么......可选参数在Swashbuckle中导致null异常。Asp.Netpore

我使用与ASPNET-API的版本Swashbuckle整合： https://github.com/Microsoft/aspnet-api-versioning/wiki/Swashbuckle-Integration

控制器动作：

[HttpGet("{id}")] 
public IActionResult GetPerson(int id, [FromQuery] bool? includeContactInfo = null) 
{ 
    var includeInfo = (includeContactInfo.HasValue && includeContactInfo.Value == true); 
    var person = _repo.GetPerson(id, includeInfo); 
    if (person == null) 
    { 
     return NotFound(); 
    } 

    if (includeInfo) 
    { 
     // using AutoMapper to map between entity and dto 
     var personFullDto = Mapper.Map<PersonFullDto>(person); 
     return Ok(personFullDto); 
    } 

    var personBasicDto = Mapper.Map<PersonBasicDto>(person); 
    return Ok(personBasicDto); 
}

这里是ConfigureServices从我startup.cs配置方法：

public void ConfigureServices(IServiceCollection services) 
{ 
    services.AddMvcCore().AddVersionedApiExplorer(o => o.GroupNameFormat = "'v'VVV"); 
    services.AddMvc(); 

    services.AddApiVersioning(o => 
    { 
     o.ReportApiVersions = true; 
     o.DefaultApiVersion = new Microsoft.AspNetCore.Mvc.ApiVersion(1, 0); 
    }); 

    services.AddSwaggerGen(options => 
    { 
     var provider = services.BuildServiceProvider().GetRequiredService<IApiVersionDescriptionProvider>(); 
     foreach (var description in provider.ApiVersionDescriptions) 
     { 
      options.SwaggerDoc(description.GroupName, CreateInfoForApiVersion(description)); 
     } 
     options.OperationFilter<SwaggerDefaultValues>(); 
     options.IncludeXmlComments(XmlCommentsFilePath); 
    }); 

    var connectString = Startup.Configuration["connectionStrings:ContactsAppDb"]; 
    services.AddDbContext<ContactsDbContext>(o => o.UseSqlServer(connectString)); 
    services.AddScoped<IContactsRepository, ContactsRepository>(); 
} 


public void Configure(IApplicationBuilder app, IHostingEnvironment env, IApiVersionDescriptionProvider provider) 
{ 
    if (env.IsEnvironment("PROD")) 
    { 
     app.UseExceptionHandler(); 
    } 
    else 
    { 
     app.UseDeveloperExceptionPage(); 
    } 

    app.UseStatusCodePages(); 

    AutoMapper.Mapper.Initialize(cfg => 
    { 
     cfg.CreateMap<Entities.Person, Models.PersonBasicDto>(); 
     cfg.CreateMap<Entities.Person, Models.PersonFullDto>(); 
     cfg.CreateMap<Entities.ContactInfo, Models.ContactInfoDto>(); 
    }); 

    app.UseMvc(); 

    app.UseSwagger(); 
    app.UseSwaggerUI(options => 
    { 
     // build a swagger endpoint for each discovered API version 
     foreach (var description in provider.ApiVersionDescriptions) 
     { 
      options.SwaggerEndpoint($"/swagger/{description.GroupName}/swagger.json", description.GroupName.ToUpperInvariant()); 
     } 
    }); 
}

我也是用的SwaggerDefaultValues.cs类，从 https://github.com/Microsoft/aspnet-api-versioning/wiki/Swashbuckle-Integration#aspnet-core

public class SwaggerDefaultValues : IOperationFilter 
{ 
    public void Apply(Operation operation, OperationFilterContext context) 
    { 
     foreach (var parameter in operation.Parameters.OfType<NonBodyParameter>()) 
     { 
      var description = context.ApiDescription 
            .ParameterDescriptions 
            .First(p => p.Name == parameter.Name); 

      if (parameter.Description == null) 
      { 
       parameter.Description = description.ModelMetadata.Description; 
      } 

      if (parameter.Default == null) 
      { 
       parameter.Default = description.RouteInfo.DefaultValue; 
      } 

      parameter.Required |= !description.RouteInfo.IsOptional; 
     } 
    } 
}

当我浏览到扬鞭URL，下面的代码行失败（在SwaggerDefaultValues.cs类）：

parameter.Default = description.RouteInfo.DefaultValue;

当我检查用于includeContactInfo可选/查询参数description目的，description.RouteInfo为空。

错误消息：

Object reference not set to an instance of an object.

堆栈跟踪：

at ContactsApp.Services.SwaggerDefaultValues.Apply(Operation operation, OperationFilterContext context) in C:\Users\me\Documents\Visual Studio 2017\Projects\ContactsApp\ContactsApp\Services\SwaggerDefaultValues.cs:line 37 
at Swashbuckle.AspNetCore.SwaggerGen.SwaggerGenerator.CreateOperation(ApiDescription apiDescription, ISchemaRegistry schemaRegistry) 
at Swashbuckle.AspNetCore.SwaggerGen.SwaggerGenerator.CreatePathItem(IEnumerable`1 apiDescriptions, ISchemaRegistry schemaRegistry) 
at System.Linq.Enumerable.ToDictionary[TSource,TKey,TElement](IEnumerable`1 source, Func`2 keySelector, Func`2 elementSelector, IEqualityComparer`1 comparer) 
at Swashbuckle.AspNetCore.SwaggerGen.SwaggerGenerator.GetSwagger(String documentName, String host, String basePath, String[] schemes) 
at Swashbuckle.AspNetCore.Swagger.SwaggerMiddleware.<Invoke>d__6.MoveNext()

答

使用空条件运算符：

parameter.Default = description.RouteInfo?.DefaultValue;

可选参数在Swashbuckle中导致null异常。Asp.Netpore

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