Basically I used a custom stream to append the newline that asp.net web api is expecting.
Stream reqStream = Request.Content.ReadAsStreamAsync().Result;
MemoryStream tempStream = new MemoryStream();
reqStream.CopyTo(tempStream);
tempStream.Seek(0, SeekOrigin.End);
StreamWriter writer = new StreamWriter(tempStream);
writer.WriteLine();
writer.Flush();
tempStream.Position = 0;
StreamContent streamContent = new StreamContent(tempStream);
foreach(var header in Request.Content.Headers)
{
streamContent.Headers.Add(header.Key, header.Value);
}
// Read the form data and return an async task.
await streamContent.ReadAsMultipartAsync(provider);
and add following code in web.config
<system.web>
<httpRuntime maxRequestLength="30000000" />
</system.web>
<system.webServer>
<security>
<requestFiltering>
<requestLimits maxAllowedContentLength="30000000" />
</requestFiltering>
</security>
</system.webServer>
Hope this helps.
My application was experiencing this error periodically too. Upgrading to WEB API 2.1 did nothing and the exception message is completely useless.
I think what was actually happening though is it was choking on large files. Increasing my max request limits in web.config seemed to fix it right up.
<system.web>
<httpRuntime maxRequestLength="30000" />
</system.web>
<system.webServer>
<security>
<requestFiltering>
<requestLimits maxAllowedContentLength="30000" />
</requestFiltering>
</security>
</system.webServer>
(This sets the ceiling to 30 megs. Set it to whatever you need. More info [here](https://msdn.microsoft.com/en-us/library/system.web.configuration.httpruntimesection.maxrequestlength(v=vs.100).aspx))
