Hot to write a FileUpload method in a WebAPI using NSwag?

Question

I'm currently working on a ASP.NET WebAPI 2 (.NET 4.7.1) using NSwag 13.19.0. I managed to integrate a file upload into my WebAPI, like described here by @squadwuschel: NSwag Wep Api 2 multipart/form-data Attribute / file upload

Strangely, it only works, if I use the SchemaType.Swagger2. If I use SchemaType.OpenApi3, no file upload button will be rendered in the Swagger UI in the browser:

File Upload in Swagger UI for SchemaType.Swagger2:

File Upload in Swagger UI for SchemaType.OpenApi3:

I expected that the file upload always will be rendered the same way in the Swagger UI, no matter what SchemaType I use. So I have no further ideas, what I can do to solve this problem. Has anyone ever had the same problem and perhaps found a solution?

Thanks in advance.

Best regards, Tom

Answer 1

I found the solution for the problem:

For SchemaType.OpenApi3 (OpenApi Sepcification 3.0) you'll have to configure the parameter as a body parameter in the IOperationProcessor implementation, instead of adding SwaggerParameters to context.OperationDescription.Operation.Parameters:

context.OperationDescription.Operation.RequestBody = new OpenApiRequestBody
{
    IsRequired = true,
    Content =
    {
        ["multipart/form-data"] = new OpenApiMediaType
        {
            Schema = new JsonSchema
            {
                Type = JsonObjectType.Object,
                Properties =
                {
                    ["your parameter"] = new JsonSchemaProperty
                    {
                        Type = JsonObjectType.String,
                        Format = JsonFormatStrings.Binary,
                        IsNullableRaw = false,
                        Description = "some description",
                    }
                }
            }
        }
    }
};