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How does one correctly implement a MediaTypeFormatter to handle requests of type 'multipart/mixed'?

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感情败类 2020-12-24 02:44

Consider a web service written in ASP.NET Web API to accept any number files as a \'multipart/mixed\' request. The helper method mat look as follows (assuming _client

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  • 暗喜
    暗喜 (楼主)
    2020-12-24 03:03

    Have a look at this forum: http://forums.asp.net/t/1777847.aspx/1?MVC4+Beta+Web+API+and+multipart+form+data

    Here is a snippet of code (posted by imran_ku07) that might help you implement a custom formatter to handle the multipart/form-data:

    public class MultiFormDataMediaTypeFormatter : FormUrlEncodedMediaTypeFormatter
{
    public MultiFormDataMediaTypeFormatter() : base()
    {
        this.SupportedMediaTypes.Add(new MediaTypeHeaderValue("multipart/form-data"));
    }

    protected override bool CanReadType(Type type)
    {
        return true;
    }

    protected override bool CanWriteType(Type type)
    {
        return false;
    }

    protected override Task OnReadFromStreamAsync(Type type, Stream stream, HttpContentHeaders contentHeaders, FormatterContext formatterContext)
    {
        var contents = formatterContext.Request.Content.ReadAsMultipartAsync().Result;
        return Task.Factory.StartNew(() =>
        {
            return new MultiFormKeyValueModel(contents);
        });
    }

    class MultiFormKeyValueModel : IKeyValueModel
    {
        IEnumerable _contents;
        public MultiFormKeyValueModel(IEnumerable contents)
        {
            _contents = contents;
        }


        public IEnumerable Keys
        {
            get
            {
                return _contents.Cast();
            }
        }

        public bool TryGetValue(string key, out object value)
        {
            value = _contents.FirstDispositionNameOrDefault(key).ReadAsStringAsync().Result;
            return true;
        }
    }
}



    You then need to add this formatter to your application. If doing self-host you can simply add it by including:
    


    config.Formatters.Insert(0, new MultiFormDataMediaTypeFormatter());

    


    before instantiating the HttpSelfHostServer class.
    


    -- EDIT --
    


    To parse binary streams you'll need another formatter. Here is one that I am using to parse images in one of my work projects.
    


    class JpegFormatter : MediaTypeFormatter
{
    protected override bool CanReadType(Type type)
    {
        return (type == typeof(Binary));
    }

    protected override bool CanWriteType(Type type)
    {
        return false;
    }

    public JpegFormatter()
    {
        SupportedMediaTypes.Add(new MediaTypeHeaderValue("image/jpeg"));
        SupportedMediaTypes.Add(new MediaTypeHeaderValue("image/jpg"));
        SupportedMediaTypes.Add(new MediaTypeHeaderValue("image/png"));
    }

    protected override Task OnReadFromStreamAsync(Type type, Stream stream, HttpContentHeaders contentHeaders, FormatterContext formatterContext)
    {
        return Task.Factory.StartNew(() =>
            {
                byte[] fileBytes = new byte[stream.Length];
                stream.Read(fileBytes, 0, (int)fileBytes.Length);

               return (object)new Binary(fileBytes);
            }); 
    }

    protected override Task OnWriteToStreamAsync(Type type, object value, Stream stream, HttpContentHeaders contentHeaders, FormatterContext formatterContext, TransportContext transportContext)
    {
        throw new NotImplementedException();
    }
}



    In your controller/action you'll want to do something along the lines of:
    


    public HttpResponseMessage UploadImage(Binary File) {
 //do something with your file
}

    
    
    
             
    
                                                        
    
            
            
    
              
                
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