Transmitting Binary Data via OpenAPI on Azure Functions

01-run-byte-array.cs

public static class BinaryDataHttpTrigger
{
    [FunctionName(nameof(BinaryDataHttpTrigger.RunByteArray))]
    [OpenApiOperation(operationId: "run.bytearray", tags: new[] { "bytearray" }, ...)]
    [OpenApiSecurity("function_key", SecuritySchemeType.ApiKey, Name = "code", In = OpenApiSecurityLocationType.Query)]

    [OpenApiRequestBody(contentType: "text/plain", bodyType: typeof(byte[]), ...)]

    [OpenApiResponseWithBody(statusCode: HttpStatusCode.OK, contentType: "image/png", bodyType: typeof(byte[]), ...)]

    public static async Task<IActionResult> RunByteArray(
        [HttpTrigger(AuthorizationLevel.Function, "POST", Route = "bytearray")] HttpRequest req,
        ILogger log)
    {
        var payload = default(string);
        using (var reader = new StreamReader(req.Body))
        {
            payload = await reader.ReadToEndAsync().ConfigureAwait(false);
        }

        var content = Convert.FromBase64String(payload);

        var result = new FileContentResult(content, "image/png");

        return result;
    }
}

02-run-byte-array.yaml

paths:
  /bytearray:
    post:
      requestBody:

        content:
          text/plain:
            schema:
              type: string
              format: base64

      responses:
        '200':

          content:
            image/png:
              schema:
                type: string
                format: base64

03-run-multi-part-form-data.cs

public static class BinaryDataHttpTrigger
{
    [FunctionName(nameof(BinaryDataHttpTrigger.RunMultiPartFormData))]
    [OpenApiOperation(operationId: "run.multipart.formdata", tags: new[] { "multipartformdata" }, ...)]
    [OpenApiSecurity("function_key", SecuritySchemeType.ApiKey, Name = "code", In = OpenApiSecurityLocationType.Query)]

    [OpenApiRequestBody(contentType: "multipart/form-data", bodyType: typeof(MultiPartFormDataModel), ...)]

    [OpenApiResponseWithBody(statusCode: HttpStatusCode.OK, contentType: "image/png", bodyType: typeof(byte[]), ...)]

    public static async Task<IActionResult> RunMultiPartFormData(
        [HttpTrigger(AuthorizationLevel.Function, "POST", Route = "form/multipart")] HttpRequest req,
        ILogger log)
    {
        var files = req.Form.Files;
        var file = files[0];

        var content = default(byte[]);
        using (var ms = new MemoryStream())
        {
            await file.CopyToAsync(ms).ConfigureAwait(false);
            content = ms.ToArray();
        }

        var result = new FileContentResult(content, "image/png");

        return result;
    }
}

public class MultiPartFormDataModel
{
    public int Id { get; set; }
    public string Description { get; set; }
    public byte[] Image { get; set; }
}

04-run-multi-part-form-data.yaml

paths:
  /form/multipart:
    post:
      requestBody:

        content:
          multipart/form-data:
            schema:
              $ref: '#/components/schemas/multiPartFormDataModel'

      responses:
        '200':

          content:
            image/png:
              schema:
                type: string
                format: base64

components:
  schemas:
    multiPartFormDataModel:
      type: object
      properties:
        id:
          type: integer
          format: int32
        description:
          type: string

        image:
          type: string
          format: base64