Openapi Binary File Response - Aspnetcore

Describe binary file responses

ASP.NET Core 11 introduces support for generating OpenAPI descriptions for operations that return binary file responses. This support maps the FileContentResult result type to an OpenAPI schema with type: string and format: binary.

Minimal APIs

Use the Produces<T> extension method with T of FileContentResult to specify the response type and content type:

csharp

app.MapPost("/filecontentresult", () =>
{
    var content = "This endpoint returns a FileContentResult!"u8.ToArray();
    return TypedResults.File(content);
})
.Produces<FileContentResult>(contentType: MediaTypeNames.Application.Octet);

Controllers

Use the ProducesResponseType<T> attribute with T of FileContentResult to specify the response type and content type:

csharp

[HttpPost("filecontentresult")]
[ProducesResponseType<FileContentResult>(StatusCodes.Status200OK, MediaTypeNames.Application.Octet)]
public IActionResult PostFileContentResult()
{
    var content = "This endpoint returns a FileContentResult!"u8.ToArray();
    return new FileContentResult(content, MediaTypeNames.Application.Octet);
}

The generated OpenAPI document describes the endpoint response as:

yaml

responses:
  '200':
    description: OK
    content:
      application/octet-stream:
        schema:
          $ref: '#/components/schemas/FileContentResult'

The FileContentResult is defined in components/schemas as:

yaml

components:
  schemas:
    FileContentResult:
      type: string
      format: binary