File upload example for grapevine - asp.net-web-api

Question

I am new to Web API and REST services and looking to build a simple REST server which accepts file uploads. I found out grapevine which is simple and easy to understand. I couldn't find any file upload example?
This is an example using System.Web.Http
var streamProvider = new MultipartFormDataStreamProvider(ServerUploadFolder);
await Request.Content.ReadAsMultipartAsync(streamProvider);
but the grapevine Request property does not have any method to do that. Can someone point me to an example?

Answer 1

If you are trying to upload a file as a binary payload, see this question/answer on GitHub.
If you are trying to upload a file from a form submission, that will be a little bit trickier, as the multi-part payload parsers haven't been added yet, but it is still possible.
The following code sample is complete untested, and I just wrote this off the top of my head, so it might not be the best solution, but it's a starting point:
public static class RequestExtensions
{
public static IDictionary<string, string> ParseFormUrlEncoded(this IHttpRequest request)
{
var data = new Dictionary<string, string>();
foreach (var tuple in request.Payload.Split('='))
{
var parts = tuple.Split('&');
var key = Uri.UnescapeDataString(parts[0]);
var val = Uri.UnescapeDataString(parts[1]);
if (!data.ContainsKey(key)) data.Add(key, val);
}
return data;
}
public static IDictionary<string, FormElement> ParseFormData(this IHttpRequest request)
{
var data = new Dictionary<string, FormElement>();
var boundary = GetBoundary(request.Headers.Get("Content-Type"));
if (boundary == null) return data;
foreach (var part in request.Payload.Split(new[] { boundary }, StringSplitOptions.RemoveEmptyEntries))
{
var element = new FormElement(part);
if (!data.ContainsKey(element.Name)) data.Add(element.Name, element);
}
return data;
}
private static string GetBoundary(string contenttype)
{
if (string.IsNullOrWhiteSpace(contenttype)) return null;
return (from part in contenttype.Split(';', ',')
select part.TrimStart().TrimEnd().Split('=')
into parts
where parts[0].Equals("boundary", StringComparison.CurrentCultureIgnoreCase)
select parts[1]).FirstOrDefault();
}
}
public class FormElement
{
public string Name => _dispositionParams["name"];
public string FileName => _dispositionParams["filename"];
public Dictionary<string, string> Headers { get; private set; }
public string Value { get; }
private Dictionary<string, string> _dispositionParams;
public FormElement(string data)
{
var parts = data.Split(new [] { "\r\n\r\n", "\n\n" }, StringSplitOptions.None);
Value = parts[1];
ParseHeaders(parts[0]);
ParseParams(Headers["Content-Disposition"]);
}
private void ParseHeaders(string data)
{
Headers = data.TrimStart().TrimEnd().Split(new[] {"\r\n", "\n"}, StringSplitOptions.RemoveEmptyEntries).Select(header => header.Split(new[] {':'})).ToDictionary(parts => parts[0].TrimStart().TrimEnd(), parts => parts[1].TrimStart().TrimEnd());
}
private void ParseParams(string data)
{
_dispositionParams = new Dictionary<string, string>();
foreach (var part in data.Split(new[] {';'}))
{
if (part.IndexOf("=") == -1) continue;
var parts = part.Split(new[] {'='});
_dispositionParams.Add(parts[0].TrimStart(' '), parts[1].TrimEnd('"').TrimStart('"'));
}
}
}
If you are looking for something async to use immediately, you can try to implement the answer to this stackoverflow question, which has not been tested by me.