Middleware to expose Swagger JSON endpoints from API's built on ASP.NET Core


Keywords
swagger, documentation, discovery, webapi, help, aspnet, aspnetcore
License
MIT
Install
Install-Package Swashbuckle.AspNetCore.Swagger -Version 5.0.0

Documentation

📣 Important notice if you're upgrading between major versions!
* If you're upgrading from 4.x to 5.x, there's several breaking changes to be aware of. See the release notes for details
* If you're making the jump from 3.x to 4.x first, there be dragons there too. See those release notes here

Swashbuckle.AspNetCore

Build status

Swagger tooling for API's built with ASP.NET Core. Generate beautiful API documentation, including a UI to explore and test operations, directly from your routes, controllers and models.

In addition to its Swagger 2.0 and OpenAPI 3.0 generator, Swashbuckle also provides an embedded version of the awesome swagger-ui that's powered by the generated Swagger JSON. This means you can complement your API with living documentation that's always in sync with the latest code. Best of all, it requires minimal coding and maintenance, allowing you to focus on building an awesome API.

And that's not all ...

Once you have an API that can describe itself in Swagger, you've opened the treasure chest of Swagger-based tools including a client generator that can be targeted to a wide range of popular platforms. See swagger-codegen for more details.

Compatibility

Swashbuckle Version ASP.NET Core Swagger / OpenAPI Spec. swagger-ui ReDoc UI
master >= 2.0.0 2.0, 3.0 3.24.3 2.0.0-rc.14
5.0.0 >= 2.0.0 2.0, 3.0 3.24.3 2.0.0-rc.14
4.0.0 >= 2.0.0, < 3.0.0 2.0 3.19.5 1.22.2
3.0.0 >= 1.0.4, < 3.0.0 2.0 3.17.1 1.20.0
2.5.0 >= 1.0.4, < 3.0.0 2.0 3.16.0 1.20.0

Getting Started

  1. Install the standard Nuget package into your ASP.NET Core application.

    Package Manager : Install-Package Swashbuckle.AspNetCore -Version 5.0.0-rc5
    CLI : dotnet add package --version 5.0.0-rc5 Swashbuckle.AspNetCore
    
  2. In the ConfigureServices method of Startup.cs, register the Swagger generator, defining one or more Swagger documents.

    using Microsoft.OpenApi.Models;
    services.AddMvc();
    
    services.AddSwaggerGen(c =>
    {
        c.SwaggerDoc("v1", new OpenApiInfo { Title = "My API", Version = "v1" });
    });
  3. Ensure your API actions and parameters are decorated with explicit "Http" and "From" bindings.

    [HttpPost]
    public void CreateProduct([FromBody]Product product)
    ...
    [HttpGet]
    public IEnumerable<Product> SearchProducts([FromQuery]string keywords)
    ...

    NOTE: If you omit the explicit parameter bindings, the generator will describe them as "query" params by default.

  4. In the Configure method, insert middleware to expose the generated Swagger as JSON endpoint(s)

    app.UseSwagger();

    At this point, you can spin up your application and view the generated Swagger JSON at "/swagger/v1/swagger.json."

  5. Optionally, insert the swagger-ui middleware if you want to expose interactive documentation, specifying the Swagger JSON endpoint(s) to power it from.

    app.UseSwaggerUI(c =>
    {
        c.SwaggerEndpoint("/swagger/v1/swagger.json", "My API V1");
    });

    Now you can restart your application and check out the auto-generated, interactive docs at "/swagger".

System.Text.Json (STJ) vs Newtonsoft

In versions prior to 5.0.0, Swashbuckle will generate Schema's (descriptions of the data types exposed by an API) based on the behavior of the Newtonsoft serializer. This made sense because that was the serializer that shipped with ASP.NET Core at the time. However, since version 3.0.0, ASP.NET Core introduces a new serializer System.Text.Json (STJ) out-of-the-box, and if you want to continue using Newtonsoft, you need to install a separate package and explicitly opt-in. From Swashbuckle 5.0.0 and beyond a similar pattern is used. That is, out-of-the-box Swashbuckle will assume you're using the STJ serializer and generate Schema's based on it's behavior. If you're using Newtonsoft, then you'll need to install a separate Swashbuckle package and explicitly opt-in. This is a required step, regardless of which version of ASP.NET Core you're using.

In summary ...

If you're using System.Text.Json (STJ), then the setup described above will be sufficient, and STJ options/attributes will be automatically honored by the Swagger generator.

If you're using Newtonsoft, then you'll need to install a separate package and explicitly opt-in to ensure that Newtonsoft settings/attributes are automatically honored by the Swagger generator:

Package Manager : Install-Package Swashbuckle.AspNetCore.Newtonsoft -Version 5.0.0-rc5
CLI : dotnet add package --version 5.0.0-rc5 Swashbuckle.AspNetCore.Newtonsoft
services.AddMvc();

services.AddSwaggerGen(c =>
{
    c.SwaggerDoc("v1", new OpenApiInfo { Title = "My API", Version = "v1" });
});
services.AddSwaggerGenNewtonsoftSupport() // explicit opt-in

Swashbuckle, ApiExplorer, and Routing

Swashbuckle relies heavily on ApiExplorer, the API metadata layer that ships with ASP.NET Core. If you're using the AddMvc helper to bootstrap the MVC stack, then ApiExplorer will be automatically registered and SB will work without issue. However, if you're using AddMvcCore for a more paired-down MVC stack, you'll need to explicitly add the ApiExplorer service:

services.AddMvcCore()
    .AddApiExplorer();

Additionally, if you are using conventional routing (as opposed to attribute routing), any controllers and the actions on those controllers that use conventional routing will not be represented in ApiExplorer, which means Swashbuckle won't be able to find those controllers and generate Swagger operations from them. For instance:

app.UseMvc(routes =>
{
   // SwaggerGen won't find controllers that are routed via this technique.
   routes.MapRoute("default", "{controller=Home}/{action=Index}/{id?}");
});

You must use attribute routing for any controllers that you want represented in your Swagger document(s):

[Route("example")]
public class ExampleController : Controller
{
    [HttpGet("")]
    public IActionResult DoStuff() { /**/ }
}

Refer to the routing documentation for more information.

Components

Swashbuckle consists of multiple components that can be used together or individually dependening on your needs. At its core, there's a Swagger generator, middleware to expose it as JSON endpoints, and a packaged version of the swagger-ui. These 3 packages can be installed with the Swashbuckle.AspNetCore "metapackage" and will work together seamlessly (see Getting Started) to provide beautiful API docs that are automatically generated from your code.

Additionally, there's add-on packages (CLI tools, an alternate UI etc.) that you can optionally install and configure as needed.

"Core" Packages (i.e. installed via Swashbuckle.AspNetCore)

Package Description
Swashbuckle.AspNetCore.Swagger Exposes Swagger JSON endpoints. It expects an implementation of ISwaggerProvider to be registered in the DI container, which it queries to retrieve OpenAPIDocument(s) that are then exposed as serialized JSON
Swashbuckle.AspNetCore.SwaggerGen Injects an implementation of ISwaggerProvider that can be used by the above component. This particular implementation generates OpenApiDocument(s) from your routes, controllers and models
Swashbuckle.AspNetCore.SwaggerUI Exposes an embedded version of the swagger-ui. You specify the API endpoints where it can obtain Swagger JSON, and it uses them to power interactive docs for your API

Additional Packages

Package Description
Swashbuckle.AspNetCore.Annotations Includes a set of custom attributes that can be applied to controllers, actions and models to enrich the generated Swagger
Swashbuckle.AspNetCore.Cli Provides a command line interface for retrieving Swagger directly from a startup assembly, and writing to file
Swashbuckle.AspNetCore.ReDoc Exposes an embedded version of the ReDoc UI (an alternative to swagger-ui)

Community Packages

These packages are provided by the open-source community.

Package Description
Swashbuckle.AspNetCore.Filters Some useful Swashbuckle filters which add additional documentation, e.g. request and response examples, a file upload button, etc. See its Readme for more details
Unchase.Swashbuckle.AspNetCore.Extensions Some useful extensions (filters), which add additional documentation, e.g. hide PathItems for unaccepted roles, fix enums for client code generation, etc. See its Readme for more details
MicroElements.Swashbuckle.FluentValidation Use FluentValidation rules instead of ComponentModel attributes to augment generated Swagger Schemas
Swashbuckle.AspNetCore.AzureFunctions Use Swashbuckle with Azure Functions 2.0

Configuration & Customization

The steps described above will get you up and running with minimal setup. However, Swashbuckle offers a lot of flexibility to customize as you see fit. Check out the table below for the full list of options:

Swashbuckle.AspNetCore.Swagger

Change the Path for Swagger JSON Endpoints

By default, Swagger JSON will be exposed at the following route - "/swagger/{documentName}/swagger.json". If necessary, you can change this when enabling the Swagger middleware. Custom routes MUST include the {documentName} parameter.

app.UseSwagger(c =>
{
    c.RouteTemplate = "api-docs/{documentName}/swagger.json";
})

NOTE: If you're using the SwaggerUI middleware, you'll also need to update its configuration to reflect the new endpoints:

app.UseSwaggerUI(c =>
{
    c.SwaggerEndpoint("/api-docs/v1/swagger.json", "My API V1");
})

Modify Swagger with Request Context

If you need to set some Swagger metadata based on the current request, you can configure a filter that's executed prior to serializing the document.

app.UseSwagger(c =>
{
    c.PreSerializeFilters.Add((swagger, httpReq) =>
    {
        swagger.Servers = new List<OpenApiServer> { new OpenApiServer { Url = $"{httpReq.Scheme}://{httpReq.Host.Value}" } };
    });
});

The OpenApiDocument and the current HttpRequest are both passed to the filter. This provides a lot of flexibility. For example, you can add an explicit API server based on the "Host" header (as shown), or you could inspect session information or an Authorization header and remove operations from the document based on user permissions.

Serialize Swagger in the 2.0 format

By default, Swashbuckle will generate and expose Swagger JSON in version 3.0 of the specification, officially called the OpenAPI Specification. However, to support backwards compatibility, you can opt to continue exposing it in the 2.0 format with the following option:

app.UseSwagger(c =>
{
    c.SerializeAsV2 = true;
});

Swashbuckle.AspNetCore.SwaggerGen

Assign Explicit OperationIds

In Swagger, operations MAY be assigned an operationId. This ID MUST be unique among all operations described in the API. Tools and libraries (e.g. client generators) MAY use the operationId to uniquely identify an operation, therefore, it is RECOMMENDED to follow common programming naming conventions.

Auto-generating an ID that matches these requirements, while also providing a name that would be meaningful in client libraries is a non-trivial task and so, Swashbuckle omits the operationId by default. However, if neccessary, you can assign operationIds by decorating individual routes OR by providing a custom strategy.

Option 1) Decorate routes with a Name property

[HttpGet("{id}", Name = "GetProductById")]
public IActionResult Get(int id) // operationId = "GetProductById"

Option 2) Provide a custom strategy

// Startup.cs
services.AddSwaggerGen(c =>
{
    ...
    
    // Use method name as operationId
    c.CustomOperationIds(apiDesc =>
    {
        return apiDesc.TryGetMethodInfo(out MethodInfo methodInfo) ? methodInfo.Name : null;
    });
})

// ProductsController.cs
[HttpGet("{id}")]
public IActionResult GetProductById(int id) // operationId = "GetProductById"

NOTE: With either approach, API authors are responsible for ensuring the uniqueness of operationIds across all Operations

List Operation Responses

By default, Swashbuckle will generate a "200" response for each operation. If the action returns a response DTO, then this will be used to generate a schema for the response body. For example ...

[HttpPost("{id}")]
public Product GetById(int id)

Will produce the following response metadata:

responses: {
  200: {
    description: "Success",
    content: {
      "application/json": {
        schema: {
          $ref: "#/components/schemas/Product"
        }
      }
    }
  }
}

Explicit Responses

If you need to specify a different status code and/or additional responses, or your actions return IActionResult instead of a response DTO, you can explicitly describe responses with the ProducesResponseTypeAttribute that ships with ASP.NET Core. For example ...

[HttpPost("{id}")]
[ProducesResponseType(typeof(Product), 200)]
[ProducesResponseType(typeof(IDictionary<string, string>), 400)]
[ProducesResponseType(500)]
public IActionResult GetById(int id)

Will produce the following response metadata:

responses: {
  200: {
    description: "Success",
    content: {
      "application/json": {
        schema: {
          $ref: "#/components/schemas/Product"
        }
      }
    }
  },
  400: {
    description: "Bad Request",
    content: {
      "application/json": {
        schema: {
          type: "object",
          additionalProperties: {
            type: "string"
          }
        }
      }
    }
  },
  500: {
    description: "Server Error",
    content: {}
  }
}

Flag Required Parameters and Schema Properties

In a Swagger document, you can flag parameters and schema properties that are required for a request. If a parameter (top-level or property-based) is decorated with the BindRequiredAttribute or RequiredAttribute, then Swashbuckle will automatically flag it as a "required" parameter in the generated Swagger:

// ProductsController.cs
public IActionResult Search([FromQuery, BindRequired]string keywords, [FromQuery]PagingParams pagingParams)
{
    if (!ModelState.IsValid)
        return BadRequest(ModelState);
    ...
}

// SearchParams.cs
public class PagingParams
{
    [Required]
    public int PageNo { get; set; }

    public int PageSize { get; set; }
}

In addition to parameters, Swashbuckle will also honor the RequiredAttribute when used in a model that's bound to the request body. In this case, the decorated properties will be flagged as "required" properties in the body description:

// ProductsController.cs
public IActionResult Create([FromBody]Product product)
{
    if (!ModelState.IsValid)
        return BadRequest(ModelState);
    ...
}

// Product.cs
public class Product
{
    [Required]
    public string Name { get; set; }

    public string Description { get; set; }
}

Include Descriptions from XML Comments

To enhance the generated docs with human-friendly descriptions, you can annotate controller actions and models with Xml Comments and configure Swashbuckle to incorporate those comments into the outputted Swagger JSON:

  1. Open the Properties dialog for your project, click the "Build" tab and ensure that "XML documentation file" is checked. This will produce a file containing all XML comments at build-time.

    At this point, any classes or methods that are NOT annotated with XML comments will trigger a build warning. To suppress this, enter the warning code "1591" into the "Suppress warnings" field in the properties dialog.

  2. Configure Swashbuckle to incorporate the XML comments on file into the generated Swagger JSON:

    services.AddSwaggerGen(c =>
    {
        c.SwaggerDoc("v1",
            new OpenApiInfo
            {
                Title = "My API - V1",
                Version = "v1"
            }
         );
    
         var filePath = Path.Combine(System.AppContext.BaseDirectory, "MyApi.xml");
         c.IncludeXmlComments(filePath);
    }
  3. Annotate your actions with summary, remarks and response tags:

    /// <summary>
    /// Retrieves a specific product by unique id
    /// </summary>
    /// <remarks>Awesomeness!</remarks>
    /// <response code="200">Product created</response>
    /// <response code="400">Product has missing/invalid values</response>
    /// <response code="500">Oops! Can't create your product right now</response>
    [HttpGet("{id}")]
    [ProducesResponseType(typeof(Product), 200)]
    [ProducesResponseType(typeof(IDictionary<string, string>), 400)]
    [ProducesResponseType(500)]
    public Product GetById(int id)
  4. You can also annotate types with summary and example tags:

    public class Product
    {
        /// <summary>
        /// The name of the product
        /// </summary>
        /// <example>Men's basketball shoes</example>
        public string Name { get; set; }
    
        /// <summary>
        /// Quantity left in stock
        /// </summary>
        /// <example>10</example>
        public int AvailableStock { get; set; }
    }
  5. Rebuild your project to update the XML Comments file and navigate to the Swagger JSON endpoint. Note how the descriptions are mapped onto corresponding Swagger fields.

NOTE: You can also provide Swagger Schema descriptions by annotating your API models and their properties with summary tags. If you have multiple XML comments files (e.g. separate libraries for controllers and models), you can invoke the IncludeXmlComments method multiple times and they will all be merged into the outputted Swagger JSON.

Provide Global API Metadata

In addition to "PathItems", "Operations" and "Responses", which Swashbuckle generates for you, Swagger also supports global metadata (see https://swagger.io/specification/#oasObject). For example, you can provide a full description for your API, terms of service or even contact and licensing information:

c.SwaggerDoc("v1",
    new OpenApiInfo
    {
        Title = "My API - V1",
        Version = "v1",
        Description = "A sample API to demo Swashbuckle",
        TermsOfService = new Uri("http://tempuri.org/terms"),
        Contact = new OpenApiContact
        {
            Name = "Joe Developer",
            Email = "joe.developer@tempuri.org"
        },
        License = new OpenApiLicense
        {
            Name = "Apache 2.0",
            Url = new Uri("http://www.apache.org/licenses/LICENSE-2.0.html")
        }
    }
);

TIP: Use IntelliSense to see what other fields are available.

Generate Multiple Swagger Documents

With the setup described above, the generator will include all API operations in a single Swagger document. However, you can create multiple documents if necessary. For example, you may want a separate document for each version of your API. To do this, start by defining multiple Swagger docs in Startup.cs:

services.AddSwaggerGen(c =>
{
    c.SwaggerDoc("v1", new OpenApiInfo { Title = "My API - V1", Version = "v1" });
    c.SwaggerDoc("v2", new OpenApiInfo { Title = "My API - V2", Version = "v2" });
})

Take note of the first argument to SwaggerDoc. It MUST be a URI-friendly name that uniquely identifies the document. It's subsequently used to make up the path for requesting the corresponding Swagger JSON. For example, with the default routing, the above documents will be available at "/swagger/v1/swagger.json" and "/swagger/v2/swagger.json".

Next, you'll need to inform Swashbuckle which actions to include in each document. Although this can be customized (see below), by default, the generator will use the ApiDescription.GroupName property, part of the built-in metadata layer that ships with ASP.NET Core, to make this distinction. You can set this by decorating individual actions OR by applying an application wide convention.

Decorate Individual Actions

To include an action in a specific Swagger document, decorate it with the ApiExplorerSettingsAttribute and set GroupName to the corresponding document name (case sensitive):

[HttpPost]
[ApiExplorerSettings(GroupName = "v2")]
public void Post([FromBody]Product product)

Assign Actions to Documents by Convention

To group by convention instead of decorating every action, you can apply a custom controller or action convention. For example, you could wire up the following convention to assign actions to documents based on the controller namespace.

// ApiExplorerGroupPerVersionConvention.cs
public class ApiExplorerGroupPerVersionConvention : IControllerModelConvention
{
    public void Apply(ControllerModel controller)
    {
        var controllerNamespace = controller.ControllerType.Namespace; // e.g. "Controllers.V1"
        var apiVersion = controllerNamespace.Split('.').Last().ToLower();

        controller.ApiExplorer.GroupName = apiVersion;
    }
}

// Startup.cs
public void ConfigureServices(IServiceCollection services)
{
    services.AddMvc(c =>
        c.Conventions.Add(new ApiExplorerGroupPerVersionConvention())
    );

    ...
}

Customize the Action Selection Process

When selecting actions for a given Swagger document, the generator invokes a DocInclusionPredicate against every ApiDescription that's surfaced by the framework. The default implementation inspects ApiDescription.GroupName and returns true if the value is either null OR equal to the requested document name. However, you can also provide a custom inclusion predicate. For example, if you're using an attribute-based approach to implement API versioning (e.g. Microsoft.AspNetCore.Mvc.Versioning), you could configure a custom predicate that leverages the versioning attributes instead:

c.DocInclusionPredicate((docName, apiDesc) =>
{
    if (!apiDesc.TryGetMethodInfo(out MethodInfo methodInfo)) return false;

    var versions = methodInfo.DeclaringType
        .GetCustomAttributes(true)
        .OfType<ApiVersionAttribute>()
        .SelectMany(attr => attr.Versions);

    return versions.Any(v => $"v{v.ToString()}" == docName);
});

Exposing Multiple Documents through the UI

If you're using the SwaggerUI middleware, you'll need to specify any additional Swagger endpoints you want to expose. See List Multiple Swagger Documents for more.

Omit Obsolete Operations and/or Schema Properties

The Swagger spec includes a deprecated flag for indicating that an operation is deprecated and should be refrained from use. The Swagger generator will automatically set this flag if the corresponding action is decorated with the ObsoleteAttribute. However, instead of setting a flag, you can configure the generator to ignore obsolete actions altogether:

services.AddSwaggerGen(c =>
{
    ...
    c.IgnoreObsoleteActions();
};

A similar approach can also be used to omit obsolete properties from Schemas in the Swagger output. That is, you can decorate model properties with the ObsoleteAttribute and configure Swashbuckle to omit those properties when generating JSON Schemas:

services.AddSwaggerGen(c =>
{
    ...
    c.IgnoreObsoleteProperties();
};

Omit Arbitrary Operations

You can omit operations from the Swagger output by decorating individual actions OR by applying an application wide convention.

Decorate Individual Actions

To omit a specific action, decorate it with the ApiExplorerSettingsAttribute and set the IgnoreApi flag:

[HttpGet("{id}")]
[ApiExplorerSettings(IgnoreApi = true)]
public Product GetById(int id)

Omit Actions by Convention

To omit actions by convention instead of decorating them individually, you can apply a custom action convention. For example, you could wire up the following convention to only document GET operations:

// ApiExplorerGetsOnlyConvention.cs
public class ApiExplorerGetsOnlyConvention : IActionModelConvention
{
    public void Apply(ActionModel action)
    {
        action.ApiExplorer.IsVisible = action.Attributes.OfType<HttpGetAttribute>().Any();
    }
}

// Startup.cs
public void ConfigureServices(IServiceCollection services)
{
    services.AddMvc(c =>
        c.Conventions.Add(new ApiExplorerGetsOnlyConvention())
    );

    ...
}

Customize Operation Tags (e.g. for UI Grouping)

The Swagger spec allows one or more "tags" to be assigned to an operation. The Swagger generator will assign the controller name as the default tag. This is important to note if you're using the SwaggerUI middleware as it uses this value to group operations.

You can override the default tag by providing a function that applies tags by convention. For example, the following configuration will tag, and therefore group operations in the UI, by HTTP method:

services.AddSwaggerGen(c =>
{
    ...
    c.TagActionsBy(api => api.HttpMethod);
};

Change Operation Sort Order (e.g. for UI Sorting)

By default, actions are ordered by assigned tag (see above) before they're grouped into the path-centric, nested structure of the Swagger spec. But, you can change the default ordering of actions with a custom sorting strategy:

services.AddSwaggerGen(c =>
{
    ...
    c.OrderActionsBy((apiDesc) => $"{apiDesc.ActionDescriptor.RouteValues["controller"]}_{apiDesc.HttpMethod}");
};

NOTE: This dictates the sort order BEFORE actions are grouped and transformed into the Swagger format. So, it affects the ordering of groups (i.e. Swagger "PathItems"), AND the ordering of operations within a group, in the Swagger output.

Customize Schema Id's

If the generator encounters complex parameter or response types, it will generate a corresponding JSON Schema, add it to the global components/schemas dictionary, and reference it from the operation description by unique Id. For example, if you have an action that returns a Product type, then the generated schema will be referenced as follows:

responses: {
  200: {
    description: "Success",
    content: {
      "application/json": {
        schema: {
          $ref: "#/components/schemas/Product"
        }
      }
    }
  }
}

However, if it encounters multiple types with the same name but different namespaces (e.g. RequestModels.Product & ResponseModels.Product), then Swashbuckle will raise an exception due to "Conflicting schemaIds". In this case, you'll need to provide a custom Id strategy that further qualifies the name:

services.AddSwaggerGen(c =>
{
    ...
    c.CustomSchemaIds((type) => type.FullName);
};

Override Schema for Specific Types

Out-of-the-box, Swashbuckle does a decent job at generating JSON Schemas that accurately describe your request and response payloads. However, if you're customizing serialization behavior for certain types in your API, you may need to help it out.

For example, you might have a class with multiple properties that you want to represent in JSON as a comma-separated string. To do this you would probably implement a custom JsonConverter. In this case, Swashbuckle doesn't know how the converter is implemented and so you would need to provide it with a Schema that accurately describes the type:

// PhoneNumber.cs
public class PhoneNumber
{
    public string CountryCode { get; set; }

    public string AreaCode { get; set; }

    public string SubscriberId { get; set; }
}

// Startup.cs
services.AddSwaggerGen(c =>
{
    ...
    c.MapType<PhoneNumber>(() => new OpenApiSchema { Type = "string" });
};

Extend Generator with Operation, Schema & Document Filters

Swashbuckle exposes a filter pipeline that hooks into the generation process. Once generated, individual metadata objects are passed into the pipeline where they can be modified further. You can wire up custom filters to enrich the generated "Operations", "Schemas" and "Documents".

Operation Filters

Swashbuckle retrieves an ApiDescription, part of ASP.NET Core, for every action and uses it to generate a corresponding OpenApiOperation. Once generated, it passes the OpenApiOperation and the ApiDescription through the list of configured Operation Filters.

In a typical filter implementation, you would inspect the ApiDescription for relevant information (e.g. route info, action attributes etc.) and then update the OpenApiOperation accordingly. For example, the following filter lists an additional "401" response for all actions that are decorated with the AuthorizeAttribute:

// AuthResponsesOperationFilter.cs
public class AuthResponsesOperationFilter : IOperationFilter
{
    public void Apply(OpenApiOperation operation, OperationFilterContext context)
    {
        var authAttributes = context.MethodInfo.DeclaringType.GetCustomAttributes(true)
            .Union(context.MethodInfo.GetCustomAttributes(true))
            .OfType<AuthorizeAttribute>();

        if (authAttributes.Any())
            operation.Responses.Add("401", new OpenApiResponse { Description = "Unauthorized" });
    }
}

// Startup.cs
services.AddSwaggerGen(c =>
{
    ...
    c.OperationFilter<AuthResponsesOperationFilter>();
};

NOTE: Filter pipelines are DI-aware. That is, you can create filters with constructor parameters and if the parameter types are registered with the DI framework, they'll be automatically injected when the filters are instantiated

Schema Filters

Swashbuckle generates a Swagger-flavored JSONSchema for every parameter, response and property type that's exposed by your controller actions. Once generated, it passes the schema and type through the list of configured Schema Filters.

The example below adds an AutoRest vendor extension (see https://github.com/Azure/autorest/blob/master/docs/extensions/readme.md#x-ms-enum) to inform the AutoRest tool how enums should be modelled when it generates the API client.

// AutoRestSchemaFilter.cs
public class AutoRestSchemaFilter : ISchemaFilter
{
    public void Apply(OpenApiSchema schema, SchemaFilterContext context)
    {
        var type = context.Type;
        if (type.IsEnum)
        {
            schema.Extensions.Add(
                "x-ms-enum",
                new OpenApiObject
                {
                    ["name"] = new OpenApiString(type.Name),
                    ["modelAsString"] = new OpenApiBoolean(true)
                }
            );
        };
    }
}

// Startup.cs
services.AddSwaggerGen(c =>
{
    ...
    c.SchemaFilter<AutoRestSchemaFilter>();
};

Document Filters

Once an OpenApiDocument has been generated, it too can be passed through a set of pre-configured Document Filters. This gives full control to modify the document however you see fit. To ensure you're still returning valid Swagger JSON, you should have a read through the specification before using this filter type.

The example below provides a description for any tags that are assigned to operations in the document:

public class TagDescriptionsDocumentFilter : IDocumentFilter
{
    public void Apply(OpenApiDocument swaggerDoc, DocumentFilterContext context)
    {
        swaggerDoc.Tags = new List<OpenApiTag> {
            new OpenApiTag { Name = "Products", Description = "Browse/manage the product catalog" },
            new OpenApiTag { Name = "Orders", Description = "Submit orders" }
        };
    }
}

NOTE: If you're using the SwaggerUI middleware, the TagDescriptionsDocumentFilter demonstratd above could be used to display additional descriptions beside each group of Operations.

Add Security Definitions and Requirements

In Swagger, you can describe how your API is secured by defining one or more security schemes (e.g basic, api key, oauth2 etc.) and declaring which of those schemes are applicable globally OR for specific operations. For more details, take a look at the Security Requirement Object in the Swagger spec..

In Swashbuckle, you can define schemes by invoking the AddSecurityDefinition method, providing a name and an instance of OpenApiSecurityScheme. For example you can define an OAuth 2.0 - implicit flow as follows:

// Startup.cs
services.AddSwaggerGen(c =>
{
    ...

    // Define the OAuth2.0 scheme that's in use (i.e. Implicit Flow)
    c.AddSecurityDefinition("oauth2", new OpenApiSecurityScheme
    {
        Type = SecuritySchemeType.OAuth2,
        Flows = new OpenApiOAuthFlows
        {
            Implicit = new OpenApiOAuthFlow
            {
                AuthorizationUrl = new Uri("/auth-server/connect/authorize", UriKind.Relative),
                Scopes = new Dictionary<string, string>
                {
                    { "readAccess", "Access read operations" },
                    { "writeAccess", "Access write operations" }
                }
            }
        }
    });
};

NOTE: In addition to defining a scheme, you also need to indicate which operations that scheme is applicable to. You can apply schemes globally (i.e. to ALL operations) through the AddSecurityRequirement method. The example below indicates that the scheme called "oauth2" should be applied to all operations, and that the "readAccess" and "writeAccess" scopes are required. When applying schemes of type other than "oauth2", the array of scopes MUST be empty.

c.AddSwaggerGen(c =>
{
    ...

    c.AddSecurityRequirement(new OpenApiSecurityRequirement
    {
        {
            new OpenApiSecurityScheme
            {
                Reference = new OpenApiReference { Type = ReferenceType.SecurityScheme, Id = "oauth2" }
            },
            new[] { "readAccess", "writeAccess" }
        }
    });
})

If you have schemes that are only applicable for certain operations, you can apply them through an Operation filter. For example, the following filter adds OAuth2 requirements based on the presence of the AuthorizeAttribute:

// SecurityRequirementsOperationFilter.cs
public class SecurityRequirementsOperationFilter : IOperationFilter
{
    public void Apply(OpenApiOperation operation, OperationFilterContext context)
    {
        // Policy names map to scopes
        var requiredScopes = context.MethodInfo
            .GetCustomAttributes(true)
            .OfType<AuthorizeAttribute>()
            .Select(attr => attr.Policy)
            .Distinct();

        if (requiredScopes.Any())
        {
            operation.Responses.Add("401", new OpenApiResponse { Description = "Unauthorized" });
            operation.Responses.Add("403", new OpenApiResponse { Description = "Forbidden" });

            var oAuthScheme = new OpenApiSecurityScheme
            {
                Reference = new OpenApiReference { Type = ReferenceType.SecurityScheme, Id = "oauth2" }
            };

            operation.Security = new List<OpenApiSecurityRequirement>
            {
                new OpenApiSecurityRequirement
                {
                    [ oAuthScheme ] = requiredScopes.ToList()
                }
            };
        }
    }
}

NOTE: If you're using the SwaggerUI middleware, you can enable interactive OAuth2.0 flows that are powered by the emitted security metadata. See Enabling OAuth2.0 Flows for more details.

Swashbuckle.AspNetCore.SwaggerUI

Change Relative Path to the UI

By default, the Swagger UI will be exposed at "/swagger". If necessary, you can alter this when enabling the SwaggerUI middleware:

app.UseSwaggerUI(c =>
{
    c.RoutePrefix = "api-docs"
    ...
}

Change Document Title

By default, the Swagger UI will have a generic document title. When you have multiple Swagger pages open, it can be difficult to tell them apart. You can alter this when enabling the SwaggerUI middleware:

app.UseSwaggerUI(c =>
{
    c.DocumentTitle = "My Swagger UI";
    ...
}

List Multiple Swagger Documents

When enabling the middleware, you're required to specify one or more Swagger endpoints (fully qualified or relative to the UI page) to power the UI. If you provide multiple endpoints, they'll be listed in the top right corner of the page, allowing users to toggle between the different documents. For example, the following configuration could be used to document different versions of an API.

app.UseSwaggerUI(c =>
{
    c.SwaggerEndpoint("/swagger/v1/swagger.json", "V1 Docs");
    c.SwaggerEndpoint("/swagger/v2/swagger.json", "V2 Docs");
}

Apply swagger-ui Parameters

The swagger-ui ships with it's own set of configuration parameters, all described here https://github.com/swagger-api/swagger-ui/blob/v3.8.1/docs/usage/configuration.md#display. In Swashbuckle, most of these are surfaced through the SwaggerUI middleware options:

app.UseSwaggerUI(c =>
{
    c.DefaultModelExpandDepth(2);
    c.DefaultModelRendering(ModelRendering.Model);
    c.DefaultModelsExpandDepth(-1);
    c.DisplayOperationId();
    c.DisplayRequestDuration();
    c.DocExpansion(DocExpansion.None);
    c.EnableDeepLinking();
    c.EnableFilter();
    c.MaxDisplayedTags(5);
    c.ShowExtensions();
    c.EnableValidator();
    c.SupportedSubmitMethods(SubmitMethod.Get, SubmitMethod.Head);
});

NOTE: The InjectOnCompleteJavaScript and InjectOnFailureJavaScript options have been removed because the latest version of swagger-ui doesn't expose the neccessary hooks. Instead, it provides a flexible customization system based on concepts and patterns from React and Redux. To leverage this, you'll need to provide a custom version of index.html as described below.

The custom index sample app demonstrates this approach, using the swagger-ui plugin system provide a custom topbar, and to hide the info component.

Inject Custom CSS

To tweak the look and feel, you can inject additional CSS stylesheets by adding them to your wwwroot folder and specifying the relative paths in the middleware options:

app.UseSwaggerUI(c =>
{
    ...
    c.InjectStylesheet("/swagger-ui/custom.css");
}

Customize index.html

To customize the UI beyond the basic options listed above, you can provide your own version of the swagger-ui index.html page:

app.UseSwaggerUI(c =>
{
    c.IndexStream = () => GetType().Assembly
        .GetManifestResourceStream("CustomUIIndex.Swagger.index.html"); // requires file to be added as an embedded resource
});

To get started, you should base your custom index.html on the default version

Enable OAuth2.0 Flows

The swagger-ui has built-in support to participate in OAuth2.0 authorization flows. It interacts with authorization and/or token endpoints, as specified in the Swagger JSON, to obtain access tokens for subsequent API calls. See Adding Security Definitions and Requirements for an example of adding OAuth2.0 metadata to the generated Swagger.

If you're Swagger endpoint includes the appropriate security metadata, the UI interaction should be automatically enabled. However, you can further customize OAuth support in the UI with the following settings below. See https://github.com/swagger-api/swagger-ui/blob/v3.10.0/docs/usage/oauth2.md for more info:

app.UseSwaggerUI(c =>
{
    ...

    c.OAuthClientId("test-id");
    c.OAuthClientSecret("test-secret");
    c.OAuthRealm("test-realm");
    c.OAuthAppName("test-app");
    c.OAuthScopeSeparator(" ");
    c.OAuthAdditionalQueryStringParams(new Dictionary<string, string> { { "foo", "bar" }}); 
    c.OAuthUseBasicAuthenticationWithAccessCodeGrant();
});

Swashbuckle.AspNetCore.Annotations

Install and Enable Annotations

  1. Install the following Nuget package into your ASP.NET Core application.

    Package Manager : Install-Package Swashbuckle.AspNetCore.Annotations
    CLI : dotnet add package Swashbuckle.AspNetCore.Annotations
    
  2. In the ConfigureServices method of Startup.cs, enable annotations within in the Swagger config block:

    services.AddSwaggerGen(c =>
    {
       ...
    
       c.EnableAnnotations();
    });

Enrich Operation Metadata

Once annotations have been enabled, you can enrich the generated Operation metadata by decorating actions with a SwaggerOperationAttribute.

[HttpPost]

[SwaggerOperation(
    Summary = "Creates a new product",
    Description = "Requires admin privileges",
    OperationId = "CreateProduct",
    Tags = new[] { "Purchase", "Products" }
)]
public IActionResult Create([FromBody]Product product)

Enrich Response Metadata

ASP.NET Core provides the ProducesResponseTypeAttribute for listing the different responses that can be returned by an action. These attributes can be combined with XML comments, as described above, to include human friendly descriptions with each response in the generated Swagger. If you'd prefer to do all of this with a single attribute, and avoid the use of XML comments, you can use SwaggerResponseAttributes instead:

[HttpPost]
[SwaggerResponse(201, "The product was created", typeof(Product))]
[SwaggerResponse(400, "The product data is invalid")]
public IActionResult Create([FromBody]Product product)

Enrich Parameter Metadata

You can annotate top-level parameters (i.e. not part of a model) with a SwaggerParameterAttribute to include a description and/or flag it as "required" in the generated Swagger document:

[HttpGet]
public IActionResult GetProducts(
    [FromQuery, SwaggerParameter("Search keywords", Required = true)]string keywords)

Enrich Schema Metadata

The SwaggerGen package provides several extension points, including Schema Filters (described here) for customizing ALL generated Schemas. However, there may be cases where it's preferable to apply a filter to a specific Schema. For example, if you'd like to include an example for a specific type in your API. This can be done by decorating the type with a SwaggerSchemaFilterAttribute:

// Product.cs
[SwaggerSchemaFilter(typeof(ProductSchemaFilter))
public class Product
{
    ...
}

// ProductSchemaFilter.cs
public class ProductSchemaFilter : ISchemaFilter
{
    public void Apply(OpenApiSchema schema, SchemaFilterContext context)
    {
        schema.Example = new OpenApiObject
        {
            [ "Id" ] = new OpenApiInteger(1),
            [ "Description" ] = new OpenApiString("An awesome product")
        };
    }
}

Add Tag Metadata

By default, the Swagger generator will tag all operations with the controller name. This tag is then used to drive the operation groupings in the swagger-ui. If you'd like to provide a description for each of these groups, you can do so by adding metadata for each controller name tag via the SwaggerTagAttribute:

[SwaggerTag("Create, read, update and delete Products")]
public class ProductsController
{
    ...
}

NOTE: This will add the above description specifically to the tag named "Products". Therefore, you should avoid using this attribute if you're tagging Operations with something other than controller name - e.g. if you're customizing the tagging behavior with TagActionsBy.

Swashbuckle.AspNetCore.Cli

Retrieve Swagger Directly from a Startup Assembly

The Swashbuckle CLI tool can retrieve Swagger JSON directly from your application startup assembly, and write it to file. This can be useful if you want to incorporate Swagger generation into a CI/CD process, or if you want to serve it from static file at run-time.

The tool can be installed as a .NET Core Global Tools either locally or globally by creating a dotnet-tools.json file next to your .sln or .csproj file:

{
  "version": 1,
  "isRoot": true,
  "tools": {
  }
}

Then, to install tool locally, run the following command:

dotnet tool install swashbuckle.aspnetcore.cli --version 5.0.0-rc5

To restore the tool on a clean machine, run dotnet tool restore

Once this is done, you should be able to run the following command from your project root:

dotnet swagger tofile --help

Before you invoke the tofile command, you need to ensure your application is configured to expose Swagger JSON, as described in Getting Started. Once this is done, you can point to your startup assembly and generate a local Swagger JSON file with the following command:

dotnet swagger tofile --output [output] [startupassembly] [swaggerdoc]

Where ...

  • [output] is the relative path where the Swagger JSON will be output to
  • [startupassembly] is the relative path to your application's startup assembly
  • [swaggerdoc] is the name of the swagger document you want to retrieve, as configured in your startup class

Checkout the CliExample app for more inspiration. It leverages the MSBuild Exec command to generate Swagger JSON at build-time.

Swashbuckle.AspNetCore.ReDoc

Change Relative Path to the UI

By default, the ReDoc UI will be exposed at "/api-docs". If necessary, you can alter this when enabling the ReDoc middleware:

app.UseReDoc(c =>
{
    c.RoutePrefix = "docs"
    ...
}

Change Document Title

By default, the ReDoc UI will have a generic document title. You can alter this when enabling the ReDoc middleware:

app.UseReDoc(c =>
{
    c.DocumentTitle = "My API Docs";
    ...
}

Apply ReDoc Parameters

ReDoc ships with it's own set of configuration parameters, all described here https://github.com/Rebilly/ReDoc/blob/master/README.md#redoc-options-object. In Swashbuckle, most of these are surfaced through the ReDoc middleware options:

app.UseReDoc(c =>
{
    c.SpecUrl("/v1/swagger.json");
    c.UntrustedSpec();
    c.ScrollYOffset(10);
    c.HideHostname();
    c.HideDownloadButton());
    c.ExpandResponses("200,201");
    c.RequiredPropsFirst();
    c.NoAutoAuth();
    c.PathInMiddlePanel();
    c.HideLoading();
    c.NativeScrollbars();
    c.DisableSearch();
    c.OnlyRequiredInSamples();
    c.SortPropsAlphabetically();
});

Using c.SpecUrl("/v1/swagger.json") multiple times within the same UseReDoc(...) will not add multiple urls.

Inject Custom CSS

To tweak the look and feel, you can inject additional CSS stylesheets by adding them to your wwwroot folder and specifying the relative paths in the middleware options:

app.UseReDoc(c =>
{
    ...
    c.InjectStylesheet("/redoc/custom.css");
}

It is also possible to modify the theme by using the AdditionalItems property, see https://github.com/Rebilly/ReDoc/blob/master/README.md#redoc-options-object for more information.

app.UseReDoc(c =>
{
    ...
    c.ConfigObject.AdditionalItems = ...
}

Customize index.html

To customize the UI beyond the basic options listed above, you can provide your own version of the ReDoc index.html page:

app.UseReDoc(c =>
{
    c.IndexStream = () => GetType().Assembly
        .GetManifestResourceStream("CustomIndex.ReDoc.index.html"); // requires file to be added as an embedded resource
});

To get started, you should base your custom index.html on the default version