Invalid 'HttpContent' instance provided. It does not have a 'multipart' content-type header with a 'boundary' parameter

Question

I\'m writing a web api that have a post method accepting files from uploaded from UI.

public async Task> PostAsync()
    {

                 


        

Answer 1

First: Postman have a bug in handling file-based requests.

You can try adding this to your WebApiConfig.cs it worked for me:

GlobalConfiguration.Configuration.Formatters.XmlFormatter.SupportedMediaTypes.Clear();

Answer 2

You are looking on the response header which is json format and this is ok for you.

Your real problem is with the postman request, so just remove the 'Content-Type: multipart/form-data' entry from request header. It's enough to upload a file as form-data and send the request.

Look what happen when you set the Content-Type manually vs. when you not:

Postman knows to set both the content type and boundary, since you set only the content type