File upload example for grapevine

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?

score 0 · Accepted Answer · edited May 23 '17 at 11:45

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.

File upload example for grapevine

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