Swagger UI will not list my Post methods with a [FromBody] parameter

Question

I am new to Swagger UI. I need to write a public-facing API that will nicely display some documentation and that I should use Swagger. So far it displays my GET methods, and a POST with a simple string parameter in the URI. But if I add a parameter marked as [FromBody], the operation does not display.

Here is some sample code in my C# WebAPI controller:

    /// <summary>
    /// Get a list of Product Numbers that you can access.
    /// </summary>
    /// <param name="Account">Your Account Number</param>
    /// <param name="Token">A Token</param>
    /// <returns>A JSON list of product numbers.</returns>
    [HttpGet]
    [Route("api/Fulfillment/ListOfProductNumbers/{Account}/{Token}")]
    public IHttpActionResult GetListOfProductNumbers(string Account, string Token)
    {

        return Ok();
    }

    /// <summary>
    /// tester
    /// </summary>
    /// <param name="Account">x</param>
    /// <returns>x</returns>
    [HttpPost]
    [Route("api/Fulfillment/DummyOperation2/{Account}/{Token}")]
    public string PostDummyOperation2(string Account, string Token)
    {
        return "";
    }

    /// <summary>
    /// tester
    /// </summary>
    /// <param name="Account">x</param>
    /// <returns>x</returns>
    [HttpPost]
    [Route("api/Fulfillment/DummyOperation3/{Account}/{Token}/{FulfillmentInfo}")]
    public IHttpActionResult PostDummyOperation3(string Account, string Token, [FromBody] Fulfillment FulfillmentInfo)
    {
        return Ok("");
    }

And this is what I see when I run the service and go to /swagger:

And here is the SwaggerConfig.cs file:

public static void Register()
    {
        var thisAssembly = typeof(SwaggerConfig).Assembly;

        GlobalConfiguration.Configuration 
            .EnableSwagger(c =>
                {
                    // By default, the service root url is inferred from the request used to access the docs.
                    // However, there may be situations (e.g. proxy and load-balanced environments) where this does not
                    // resolve correctly. You can workaround this by providing your own code to determine the root URL.
                    //
                    //c.RootUrl(req => GetRootUrlFromAppConfig());

                    // If schemes are not explicitly provided in a Swagger 2.0 document, then the scheme used to access
                    // the docs is taken as the default. If your API supports multiple schemes and you want to be explicit
                    // about them, you can use the "Schemes" option as shown below.
                    //
                    //c.Schemes(new[] { "http", "https" });

                    // Use "SingleApiVersion" to describe a single version API. Swagger 2.0 includes an "Info" object to
                    // hold additional metadata for an API. Version and title are required but you can also provide
                    // additional fields by chaining methods off SingleApiVersion.
                    //
                    c.SingleApiVersion("v1", "FulfillmentServices");

                    // If your API has multiple versions, use "MultipleApiVersions" instead of "SingleApiVersion".
                    // In this case, you must provide a lambda that tells Swashbuckle which actions should be
                    // included in the docs for a given API version. Like "SingleApiVersion", each call to "Version"
                    // returns an "Info" builder so you can provide additional metadata per API version.
                    //
                    //c.MultipleApiVersions(
                    //    (apiDesc, targetApiVersion) => ResolveVersionSupportByRouteConstraint(apiDesc, targetApiVersion),
                    //    (vc) =>
                    //    {
                    //        vc.Version("v2", "Swashbuckle Dummy API V2");
                    //        vc.Version("v1", "Swashbuckle Dummy API V1");
                    //    });

                    // You can use "BasicAuth", "ApiKey" or "OAuth2" options to describe security schemes for the API.
                    // See https://github.com/swagger-api/swagger-spec/blob/master/versions/2.0.md for more details.
                    // NOTE: These only define the schemes and need to be coupled with a corresponding "security" property
                    // at the document or operation level to indicate which schemes are required for an operation. To do this,
                    // you'll need to implement a custom IDocumentFilter and/or IOperationFilter to set these properties
                    // according to your specific authorization implementation
                    //
                    //c.BasicAuth("basic")
                    //    .Description("Basic HTTP Authentication");
                    //
                    //c.ApiKey("apiKey")
                    //    .Description("API Key Authentication")
                    //    .Name("apiKey")
                    //    .In("header");
                    //
                    //c.OAuth2("oauth2")
                    //    .Description("OAuth2 Implicit Grant")
                    //    .Flow("implicit")
                    //    .AuthorizationUrl("http://petstore.swagger.wordnik.com/api/oauth/dialog")
                    //    //.TokenUrl("https://tempuri.org/token")
                    //    .Scopes(scopes =>
                    //    {
                    //        scopes.Add("read", "Read access to protected resources");
                    //        scopes.Add("write", "Write access to protected resources");
                    //    });

                    // Set this flag to omit descriptions for any actions decorated with the Obsolete attribute
                    //c.IgnoreObsoleteActions();

                    // Each operation be assigned one or more tags which are then used by consumers for various reasons.
                    // For example, the swagger-ui groups operations according to the first tag of each operation.
                    // By default, this will be controller name but you can use the "GroupActionsBy" option to
                    // override with any value.
                    //
                    //c.GroupActionsBy(apiDesc => apiDesc.HttpMethod.ToString());

                    // You can also specify a custom sort order for groups (as defined by "GroupActionsBy") to dictate
                    // the order in which operations are listed. For example, if the default grouping is in place
                    // (controller name) and you specify a descending alphabetic sort order, then actions from a
                    // ProductsController will be listed before those from a CustomersController. This is typically
                    // used to customize the order of groupings in the swagger-ui.
                    //
                    //c.OrderActionGroupsBy(new DescendingAlphabeticComparer());

                    // Swashbuckle makes a best attempt at generating Swagger compliant JSON schemas for the various types
                    // exposed in your API. However, there may be occasions when more control of the output is needed.
                    // This is supported through the "MapType" and "SchemaFilter" options:
                    //
                    // Use the "MapType" option to override the Schema generation for a specific type.
                    // It should be noted that the resulting Schema will be placed "inline" for any applicable Operations.
                    // While Swagger 2.0 supports inline definitions for "all" Schema types, the swagger-ui tool does not.
                    // It expects "complex" Schemas to be defined separately and referenced. For this reason, you should only
                    // use the "MapType" option when the resulting Schema is a primitive or array type. If you need to alter a
                    // complex Schema, use a Schema filter.
                    //
                    //c.MapType<ProductType>(() => new Schema { type = "integer", format = "int32" });
                    //
                    // If you want to post-modify "complex" Schemas once they've been generated, across the board or for a
                    // specific type, you can wire up one or more Schema filters.
                    //
                    //c.SchemaFilter<ApplySchemaVendorExtensions>();

                    // Set this flag to omit schema property descriptions for any type properties decorated with the
                    // Obsolete attribute 
                    //c.IgnoreObsoleteProperties();

                    // In a Swagger 2.0 document, complex types are typically declared globally and referenced by unique
                    // Schema Id. By default, Swashbuckle does NOT use the full type name in Schema Ids. In most cases, this
                    // works well because it prevents the "implementation detail" of type namespaces from leaking into your
                    // Swagger docs and UI. However, if you have multiple types in your API with the same class name, you'll
                    // need to opt out of this behavior to avoid Schema Id conflicts.
                    //
                    //c.UseFullTypeNameInSchemaIds();

                    // In accordance with the built in JsonSerializer, Swashbuckle will, by default, describe enums as integers.
                    // You can change the serializer behavior by configuring the StringToEnumConverter globally or for a given
                    // enum type. Swashbuckle will honor this change out-of-the-box. However, if you use a different
                    // approach to serialize enums as strings, you can also force Swashbuckle to describe them as strings.
                    // 
                    //c.DescribeAllEnumsAsStrings();

                    // Similar to Schema filters, Swashbuckle also supports Operation and Document filters:
                    //
                    // Post-modify Operation descriptions once they've been generated by wiring up one or more
                    // Operation filters.
                    //
                    //c.OperationFilter<AddDefaultResponse>();
                    //
                    // If you've defined an OAuth2 flow as described above, you could use a custom filter
                    // to inspect some attribute on each action and infer which (if any) OAuth2 scopes are required
                    // to execute the operation
                    //
                    //c.OperationFilter<AssignOAuth2SecurityRequirements>();

                    // Post-modify the entire Swagger document by wiring up one or more Document filters.
                    // This gives full control to modify the final SwaggerDocument. You should have a good understanding of
                    // the Swagger 2.0 spec. - https://github.com/swagger-api/swagger-spec/blob/master/versions/2.0.md
                    // before using this option.
                    //
                    //c.DocumentFilter<ApplyDocumentVendorExtensions>();

                    // If you annonate Controllers and API Types with
                    // Xml comments (http://msdn.microsoft.com/en-us/library/b2s063f7(v=vs.110).aspx), you can incorporate
                    // those comments into the generated docs and UI. You can enable this by providing the path to one or
                    // more Xml comment files.
                    //
                    //c.IncludeXmlComments(GetXmlCommentsPath());
                    c.IncludeXmlComments(string.Format(@"{0}\bin\FulfillmentServices.XML", System.AppDomain.CurrentDomain.BaseDirectory));

                    // In contrast to WebApi, Swagger 2.0 does not include the query string component when mapping a URL
                    // to an action. As a result, Swashbuckle will raise an exception if it encounters multiple actions
                    // with the same path (sans query string) and HTTP method. You can workaround this by providing a
                    // custom strategy to pick a winner or merge the descriptions for the purposes of the Swagger docs 
                    //
                    //c.ResolveConflictingActions(apiDescriptions => apiDescriptions.First());
                })
            .EnableSwaggerUi(c =>
                {
                    // Use the "InjectStylesheet" option to enrich the UI with one or more additional CSS stylesheets.
                    // The file must be included in your project as an "Embedded Resource", and then the resource's
                    // "Logical Name" is passed to the method as shown below.
                    //
                    //c.InjectStylesheet(containingAssembly, "Swashbuckle.Dummy.SwaggerExtensions.testStyles1.css");

                    // Use the "InjectJavaScript" option to invoke one or more custom JavaScripts after the swagger-ui
                    // has loaded. The file must be included in your project as an "Embedded Resource", and then the resource's
                    // "Logical Name" is passed to the method as shown above.
                    //
                    //c.InjectJavaScript(thisAssembly, "Swashbuckle.Dummy.SwaggerExtensions.testScript1.js");

                    // The swagger-ui renders boolean data types as a dropdown. By default, it provides "true" and "false"
                    // strings as the possible choices. You can use this option to change these to something else,
                    // for example 0 and 1.
                    //
                    //c.BooleanValues(new[] { "0", "1" });

                    // By default, swagger-ui will validate specs against swagger.io's online validator and display the result
                    // in a badge at the bottom of the page. Use these options to set a different validator URL or to disable the
                    // feature entirely.
                    //c.SetValidatorUrl("http://localhost/validator");
                    //c.DisableValidator();

                    // Use this option to control how the Operation listing is displayed.
                    // It can be set to "None" (default), "List" (shows operations for each resource),
                    // or "Full" (fully expanded: shows operations and their details).
                    //
                    //c.DocExpansion(DocExpansion.List);

                    // Use the CustomAsset option to provide your own version of assets used in the swagger-ui.
                    // It's typically used to instruct Swashbuckle to return your version instead of the default
                    // when a request is made for "index.html". As with all custom content, the file must be included
                    // in your project as an "Embedded Resource", and then the resource's "Logical Name" is passed to
                    // the method as shown below.
                    //
                    //c.CustomAsset("index", containingAssembly, "YourWebApiProject.SwaggerExtensions.index.html");

                    // If your API has multiple versions and you've applied the MultipleApiVersions setting
                    // as described above, you can also enable a select box in the swagger-ui, that displays
                    // a discovery URL for each version. This provides a convenient way for users to browse documentation
                    // for different API versions.
                    //
                    //c.EnableDiscoveryUrlSelector();

                    // If your API supports the OAuth2 Implicit flow, and you've described it correctly, according to
                    // the Swagger 2.0 specification, you can enable UI support as shown below.
                    //
                    //c.EnableOAuth2Support("test-client-id", "test-realm", "Swagger UI");
                });
    }

======================= EDIT =========================================

My problem was that I put the FromBody parameter FulfillmentInfo in the WebAPI route. Once I removed that, Swagger displays my method:

Solution

I had the same problem. I got the error message:

Severity    Code    Description Project File    Line    Suppression State   Suppression State
Error   MSB3073 The command "dotnet "C:\Users\<MyUser>\.nuget\packages\microsoft.extensions.apidescription.server\0.3.0-preview7.19365.7\build\/../tools/dotnet-getdocument.dll" --assembly "C:\Users\<MyUser>\Source\Repos\<MyApp>.api\<MyApp>.api\bin\Debug\netcoreapp3.0\<MyApp>.api.dll" --file-list "obj\<MyApp>.api.OpenApiFiles.cache" --framework ".NETCoreApp,Version=v3.0" --output "obj" --project "<MyApp>.api" --assets-file "C:\Users\<MyUser>\Source\Repos\<MyApp>.api\<MyApp>.api\obj\project.assets.json" --platform "AnyCPU" " exited with code 7.    <MyApp>.api C:\Users\<MyUser>\.nuget\packages\microsoft.extensions.apidescription.server\0.3.0-preview7.19365.7\build\Microsoft.Extensions.ApiDescription.Server.targets    41  

To get the real error message I had to open the Cmd-prompt and paste

dotnet "C:\Users\<MyUser>\.nuget\packages\microsoft.extensions.apidescription.server\0.3.0-preview7.19365.7\build\/../tools/dotnet-getdocument.dll" --assembly "C:\Users\<MyUser>\Source\Repos\<MyApp>.api\<MyApp>.api\bin\Debug\netcoreapp3.0\<MyApp>.api.dll" --file-list "obj\<MyApp>.api.OpenApiFiles.cache" --framework ".NETCoreApp,Version=v3.0" --output "obj" --project "<MyApp>.api" --assets-file "C:\Users\<MyUser>\Source\Repos\<MyApp>.api\<MyApp>.api\obj\project.assets.json" --platform "AnyCPU"

and hit Enter. Then I got the real error message:

System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation.
 ---> System.NotSupportedException: Ambiguous HTTP method for action - <MyApp>.api.Controllers.MyController.GetAll (<MyApp>.api). Actions require an explicit HttpMethod binding for Swagger 2.0
   at Swashbuckle.AspNetCore.SwaggerGen.SwaggerGenerator.GenerateOperations(IEnumerable`1 apiDescriptions, SchemaRepository schemaRepository)
   at Swashbuckle.AspNetCore.SwaggerGen.SwaggerGenerator.GeneratePaths(IEnumerable`1 apiDescriptions, SchemaRepository schemaRepository)
   at Swashbuckle.AspNetCore.SwaggerGen.SwaggerGenerator.GetSwagger(String documentName, String host, String basePath)
   at Microsoft.Extensions.ApiDescriptions.DocumentProvider.GenerateAsync(String documentName, TextWriter writer)
   --- End of inner exception stack trace ---
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor, Boolean wrapExceptions)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at System.Reflection.MethodBase.Invoke(Object obj, Object[] parameters)
   at Microsoft.Extensions.ApiDescription.Tool.Commands.GetDocumentCommandWorker.InvokeMethod(MethodInfo method, Object instance, Object[] arguments)
   at Microsoft.Extensions.ApiDescription.Tool.Commands.GetDocumentCommandWorker.GetDocument(String documentName, String projectName, String outputDirectory, MethodInfo generateMethod, Object service)
   at Microsoft.Extensions.ApiDescription.Tool.Commands.GetDocumentCommandWorker.GetDocuments(GetDocumentCommandContext context, IServiceProvider services)
   at Microsoft.Extensions.ApiDescription.Tool.Commands.GetDocumentCommandWorker.Process(GetDocumentCommandContext context)

Which finally led me to this thread. And I had missed to add the Route to the action method.

    [HttpGet]
    [Route("api/[controller]/Find")]
    public ActionResult Find([FromBody]FindDto dto)
    {
        var item = _service.Find(dto.Query);
        return Ok(item);
    }

Which now compiles and runs.