internal static HttpContent ToHttpContent(this IFormCollection collection, string contentTypeHeader)
{
// @PreferLinux:
// Form content types resource: https://stackoverflow.com/questions/4526273/what-does-enctype-multipart-form-data-mean/28380690
// There are three possible form content types:
// - text/plain, which should never be used and this does not handle (a request with that will not have IsFormContentType true anyway)
// - application/x-www-form-urlencoded, which doesn't handle file uploads and escapes any special characters
// - multipart/form-data, which does handle files and doesn't require any escaping, but is quite bulky for short data (due to using some content headers for each value, and a boundary sequence between them)
// A single form element can have multiple values. When sending them they are handled as separate items with the same name, not a singe item with multiple values.
// For example, a=1&a=2.
var contentType = MediaTypeHeaderValue.Parse(contentTypeHeader);
if (contentType.MediaType.Equals("application/x-www-form-urlencoded", StringComparison.OrdinalIgnoreCase)) // specification: https://url.spec.whatwg.org/#concept-urlencoded
{
return(new FormUrlEncodedContent(collection.SelectMany(formItemList => formItemList.Value.Select(value => new KeyValuePair <string, string>(formItemList.Key, value)))));
}
if (!contentType.MediaType.Equals("multipart/form-data", StringComparison.OrdinalIgnoreCase))
{
throw new Exception($"Unknown form content type `{contentType.MediaType}`.");
}
// multipart/form-data specification https://tools.ietf.org/html/rfc7578
// It has each value separated by a boundary sequence, which is specified in the Content-Type header.
// As a proxy it is probably best to reuse the boundary used in the original request as it is not necessarily random.
var delimiter = contentType.Parameters.Single(p => p.Name.Equals("boundary", StringComparison.OrdinalIgnoreCase)).Value.Trim('"');
var multipart = new MultipartFormDataContent(delimiter);
foreach (var formVal in collection)
{
foreach (var value in formVal.Value)
{
multipart.Add(new StringContent(value), formVal.Key);
}
}
foreach (var file in collection.Files)
{
var content = new StreamContent(file.OpenReadStream());
foreach (var header in file.Headers)
{
content.Headers.TryAddWithoutValidation(header.Key, (IEnumerable <string>)header.Value);
}
multipart.Add(content, file.Name, file.FileName);
}
return(multipart);
}
private static HttpContent FormCollectionToHttpContent(IFormCollection collection, string contentTypeHeader)
{
var contentType = MediaTypeHeaderValue.Parse(contentTypeHeader);
if (contentType.MediaType.Equals(MediaType.ApplicationXwww, StringComparison.OrdinalIgnoreCase)) // specification: https://url.spec.whatwg.org/#concept-urlencoded
{
return(new FormUrlEncodedContent(collection.SelectMany(formItemList => formItemList.Value.Select(value => new KeyValuePair <string, string>(formItemList.Key, value)))));
}
if (!contentType.MediaType.Equals(MediaType.MultipartFormData, StringComparison.OrdinalIgnoreCase))
{
throw new ArgumentException($"Unknown form content type `{contentType.MediaType}`.");
}
var delimiter = contentType.Parameters.Single(p => p.Name.Equals("boundary", StringComparison.OrdinalIgnoreCase)).Value.Trim('"');
var multipart = new MultipartFormDataContent(delimiter);
foreach (var formVal in collection)
{
foreach (var value in formVal.Value)
{
multipart.Add(new StringContent(value), formVal.Key);
}
}
foreach (var file in collection.Files)
{
var content = new StreamContent(file.OpenReadStream());
foreach (var header in file.Headers)
{
content.Headers.TryAddWithoutValidation(header.Key, (IEnumerable <string>)header.Value);
}
multipart.Add(content, file.Name, file.FileName);
}
return(multipart);
}
