| đź“Ł Attention early adopters - please note the package rename to Swashbuckle.AspNetCore |
|---|
| If you've been using Swashbuckle for ASP.NET Core since it's inception, you may be referencing "Swashbuckle.6.0.0-beta*" packages. These are no longer valid. The original intention had been to move the Swashbuckle project from ASP.NET WebApi onto the ASP.NET Core stack in a major version bump. However, now that Microsoft plans to support WebApi for at least 4 more years, I felt it was more appropriate to split into separate projects, allowing both to live on with their respective frameworks. Although, I personally will be devoting most of my time to this version. |
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 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.
-
Install the standard Nuget package into your ASP.NET Core application.
Install-Package Swashbuckle.AspNetCore -
In the ConfigureServices method of Startup.cs, register the Swagger generator, defining one or more Swagger documents.
services.AddMvc(); services.AddSwaggerGen(c => { c.SwaggerDoc("v1", new Info { Title = "My API", Version = "v1" }); });
-
Ensure your API actions and non-route parameters are decorated with explicit "Http" and "From" bindings.
[HttpPost] public void Create([FromBody]Product product) ... [HttpGet] public IEnumerable<Product> Search([FromQuery]string keywords) ...
NOTE: If you omit the explicit parameter bindings, the generator will describe them as "query" params by default.
-
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."
-
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".
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 Api Explorer 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 documents 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.
Swashbuckle consists of three packages - a Swagger generator, middleware to expose the generated Swagger as JSON endpoints and middleware to expose a swagger-ui that's powered by those endpoints. They can be installed together, via the "Swashbuckle.AspNetCore" meta-package, or independently according to your specific requirements. See the table below for more details.
| Package | Description |
|---|---|
| Swashbuckle.AspNetCore.Swagger | Exposes SwaggerDocument objects as a JSON API. It expects an implementation of ISwaggerProvider to be registered which it queries to retrieve Swagger document(s) before returning as serialized JSON |
| Swashbuckle.AspNetCore.SwaggerGen | Injects an implementation of ISwaggerProvider that can be used by the above component. This particular implementation automatically generates SwaggerDocument(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 |
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.SwaggerGen
- List Operations Responses
- Include Descriptions from XML Comments
- Provide Global API Metadata
- Generate Multiple Swagger Documents
- Omit Obsolete Operations and/or Schema Properties
- Omit Arbitrary Operations
- Customize Operation Tags (e.g. for UI Grouping)
- Change Operation Sort Order (e.g. for UI Sorting)
- Customize Schema Id's
- Customize Schema for Enum Types
- Override Schema for Specific Types
- Extend Generator with Operation, Schema & Document Filters
- Add Security Definitions and Requirements
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");
})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((swaggerDoc, httpReq) => swaggerDoc.Host = httpReq.Host.Value);
});The SwaggerDocument and the current HttpRequest are passed to the filter. This provides a lot of flexibility. For example, you can assign the "host" property (as shown) or you could inspect session information or an Authorization header and remove operations int the document based on user permissions.
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",
schema: {
$ref: "#/definitions/Product"
}
}
}
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 describe explicit 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(typeof(void), 500)]
public IActionResult GetById(int id)Will produce the following response metadata:
responses: {
200: {
description: "Success",
schema: {
$ref: "#/definitions/Product"
}
},
400: {
description: "Bad Request",
schema: {
type: "object",
additionalProperties: {
type: "string"
}
}
},
500: {
description: "Server Error"
}
}
To enhance the generated docs with human-friendly descriptions, you can annotate controllers and models with Xml Comments and configure Swashbuckle to incorporate those comments into the outputted Swagger JSON:
-
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.
-
Configure Swashbuckle to incorporate the XML comments on file into the generated Swagger JSON:
services.AddSwaggerGen(c => { c.SwaggerDoc("v1", new Info { Title = "My API - V1", Version = "v1" } ); var filePath = Path.Combine(PlatformServices.Default.Application.ApplicationBasePath, "MyApi.xml"); c.IncludeXmlComments(filePath); }
-
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(typeof(void), 500)] public Product GetById(int id)
-
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.
In addition to Paths, Operations and Responses, which Swashbuckle generates for you, Swagger also supports global metadata (see http://swagger.io/specification/#swaggerObject). For example, you can provide a full description for your API, terms of service or even contact and licensing information:
c.SwaggerDoc("v1",
new Info
{
Title = "My API - V1",
Version = "v1",
Description = "A sample API to demo Swashbuckle",
TermsOfService = "Knock yourself out",
Contact = new Contact
{
Name = "Joe Developer",
Email = "[email protected]"
},
License = new License
{
Name = "Apache 2.0",
Url = "http://www.apache.org/licenses/LICENSE-2.0.html"
}
}
)Use IntelliSense to see what other fields are available.
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 Info { Title = "My API - V1", Version = "v1" });
c.SwaggerDoc("v2", new Info { 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.
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)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())
);
...
}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 this instead:
c.DocInclusionPredicate((docName, apiDesc) =>
{
var versions = apiDesc.ControllerAttributes()
.OfType<ApiVersionAttribute>()
.SelectMany(attr => attr.Versions);
return versions.Any(v => $"v{v.ToString()}" == docName);
});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.
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();
};You can omit operations from the Swagger output by decorating individual actions OR by applying an application wide convention.
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)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())
);
...
}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 particularly interesting 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);
};By default, actions are ordered by assigned tag (see above) before they're grouped into the path-based, hierarchichal structure imposed by the Swagger spec. You can change this behavior with a custom sorting strategy:
services.AddSwaggerGen(c =>
{
...
c.OrderActionsBy((apiDesc) => $"{apiDesc.ControllerName()}_{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.
If the generator encounters complex parameter or response types, it will generate a corresponding JSON Schema, add it to the global "definitions" dictionary, and reference it from the operation description by unique Id. For example, if you have an action that returns a "Product" type, the generated schema will be referenced as follows:
responses: {
200: {
description: "Success",
schema: {
$ref: "#/definitions/Product"
}
}
}
However, if it encounters multiple "Product" classes under 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);
};When describing parameters and responses, Swashbuckle does its best to reflect the application's serialization settings. For example, if the CamelCaseContractResolver is enabled, Schema property names will be camelCased in the generated Swagger.
Similarly for enum types, if the StringEnumConverter is enabled, then the corresponding Schemas will list enum names rather than integer values.
For most cases this should be sufficient. However, if you need more control, Swashbuckle exposes the following options to override the default behavior:
services.AddSwaggerGen(c =>
{
...
c.DescribeAllEnumsAsStrings();
c.DescribeStringEnumsInCamelCase();
};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 Schema { Type = "string" });
};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 one or more custom filters for Operation, Schema and Document objects:
Swashbuckle retrieves an ApiDescription, part of ASP.NET Core, for every action and uses it to generate a corresponding Swagger Operation. Once generated, it passes the Operation and the ApiDescription through the list of configured Operation Filters.
In a typical filter implementation, you inspect the ApiDescription for relevant information (e.g. route info, action attributes etc.) and then update the Swagger Operation 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(Operation operation, OperationFilterContext context)
{
var authAttributes = context.ApiDescription
.ControllerAttributes()
.Union(context.ApiDescription.ActionAttributes())
.OfType<AuthorizeAttribute>();
if (authAttributes.Any())
operation.Responses.Add("401", new Response { 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
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(Schema schema, SchemaFilterContext context)
{
var typeInfo = context.SystemType.GetTypeInfo();
if (typeInfo.IsEnum)
{
schema.Extensions.Add(
"x-ms-enum",
new { name = typeInfo.Name, modelAsString = true }
);
};
}
}
// Startup.cs
services.AddSwaggerGen(c =>
{
...
c.SchemaFilter<AutoRestSchemaFilter>();
};Once a Swagger Document 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(SwaggerDocument swaggerDoc, DocumentFilterContext context)
{
swaggerDoc.Tags = new[] {
new Tag { Name = "Products", Description = "Browse/manage the product catalog" },
new Tag { Name = "Orders", Description = "Submit orders" }
};
}
}NOTE: If you're using the SwaggerUI middleware, this filter can be used to display additional descriptions beside each group of Operations.
In Swagger, you can describe how your API is secured by defining one or more Security Scheme's (e.g basic, api key, oauth etc.) and declaring which of those schemes are applicable globally OR for specific operations. For more details, take a look at the "securityDefinitions" and "security" fields in the Swagger spec.
You can use some of the options described above to include security metadata in the generated Swagger Document. The example below adds an OAuth 2.0 definition to the global metadata and a corresponding Operation Filter that uses the presence of an AuthorizeAttribute to determine which operations the scheme applies to.
// Startup.cs
services.AddSwaggerGen(c =>
{
...
// Define the OAuth2.0 scheme that's in use (i.e. Implicit Flow)
c.AddSecurityDefinition("oauth2", new OAuth2Scheme
{
Type = "oauth2",
Flow = "implicit",
AuthorizationUrl = "http://petstore.swagger.io/oauth/dialog",
Scopes = new Dictionary<string, string>
{
{ "readAccess", "Access read operations" },
{ "writeAccess", "Access write operations" }
}
});
// Assign scope requirements to operations based on AuthorizeAttribute
c.OperationFilter<SecurityRequirementsOperationFilter>();
};
// SecurityRequirementsOperationFilter.cs
public class SecurityRequirementsOperationFilter : IOperationFilter
{
private readonly IOptions<AuthorizationOptions> authorizationOptions;
public SecurityRequirementsOperationFilter(IOptions<AuthorizationOptions> authorizationOptions)
{
this.authorizationOptions = authorizationOptions;
}
public void Apply(Operation operation, OperationFilterContext context)
{
var controllerPolicies = context.ApiDescription.ControllerAttributes()
.OfType<AuthorizeAttribute>()
.Select(attr => attr.Policy);
var actionPolicies = context.ApiDescription.ActionAttributes()
.OfType<AuthorizeAttribute>()
.Select(attr => attr.Policy);
var policies = controllerPolicies.Union(actionPolicies).Distinct();
var requiredClaimTypes = policies
.Select(x => this.authorizationOptions.Value.GetPolicy(x))
.SelectMany(x => x.Requirements)
.OfType<ClaimsAuthorizationRequirement>()
.Select(x => x.ClaimType);
if (requiredClaimTypes.Any())
{
operation.Responses.Add("401", new Response { Description = "Unauthorized" });
operation.Responses.Add("403", new Response { Description = "Forbidden" });
operation.Security = new List<IDictionary<string, IEnumerable<string>>>();
operation.Security.Add(
new Dictionary<string, IEnumerable<string>>
{
{ "oauth2", requiredClaimTypes }
});
}
}
}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.
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"
...
}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");
...
}When enabling the middleware, you're required to specify one or more Swagger endpoints (fully qualified or relative to the current host) 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");
}The swagger-ui ships with it's own set of configuration parameters, all described here https://github.com/swagger-api/swagger-ui#swaggerui. In Swashbuckle, most of these are surfaced through the SwaggerUI middleware options:
app.UseSwaggerUI(c =>
{
c.EnabledValidator();
c.BooleanValues(new object[] { 0, 1 });
c.DocExpansion("full");
c.InjectOnCompleteJavaScript("/swagger-ui/on-complete.js");
c.InjectOnFailureJavaScript("/swagger-ui/on-failure.js");
c.SupportedSubmitMethods(new[] { "get", "post", "put", "patch" });
c.ShowRequestHeaders();
c.ShowJsonEditor();
});Most of them are self explanatory, mapping back to the corresponding swagger-ui docs. To inject custom JavaScript (i.e. InjectOnCompleteJavaScript and InjectOnFailureJavaScript), you'll need to add the scripts to your application and provide the relative paths as shown above. In ASP.NET Core, this is easily done by placing your script files in the wwwroot folder.
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");
}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, you can enable the UI interaction as follows:
app.UseSwaggerUI(c =>
{
...
// Provide client ID, client secret, realm and application name
c.ConfigureOAuth2("swagger-ui", "swagger-ui-secret", "swagger-ui-realm", "Swagger UI");
}