"Missing content-type boundary" sending file

I’m currently switching from an AutoRest generated client to an Nswag generated c# client. Everything seems to be working except for uploading to IFormFile parameters. There are two problems.

First, here is the swagger:

 / api / Test / UploadFile: {
	post: {
		tags: [
			"Test"
		],
		parameters: [{
				name: "file",
				schema: {
					type: "file"
				}
			}
		],
		requestBody: {
			content: {
				multipart / form - data: {
					schema: {
						type: "object",
						properties: {
							ContentType: {
								type: "string"
							},
							ContentDisposition: {
								type: "string"
							},
							Headers: {
								type: "object",
								additionalProperties: {
									type: "array",
									items: {
										type: "string"
									}
								}
							},
							Length: {
								type: "integer",
								format: "int64"
							},
							Name: {
								type: "string"
							},
							FileName: {
								type: "string"
							}
						}
					},
					encoding: {
						ContentType: {
							style: "form"
						},
						ContentDisposition: {
							style: "form"
						},
						Headers: {
							style: "form"
						},
						Length: {
							style: "form"
						},
						Name: {
							style: "form"
						},
						FileName: {
							style: "form"
						}
					}
				}
			}
		},
		responses: {
			200: {
				description: "Success"
			}
		}
	}
},

The first problem is that the generated client method has both a “body” parameter and a “file” parameter. I would expect just one… and browsing through the generated code, it looks like the “file” parameter is not even used.

public async System.Threading.Tasks.Task UploadFileAsync(FileParameter file = null, System.IO.Stream body = null, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken))

Second, when I try to use this method, I get an error from Asp.Net Core 3.0: Missing content-type boundary.

This API operation worked fine with the AutoRest generated client, so I just need to figure out what I need to do differently to get the NSwag generated client to work here.

[magiak]

Workaround https://github.com/RicoSuter/NSwag/issues/2419#issuecomment-818433921

[marinasundstrom]

In my case, it was the package version. Fixing that solved it.