WebApi 文件上傳

1. 注意給form表單加上enctype = "mult

2. 注意文件大小，IIS中默認上傳的文件大小為4MB ，超過這大小的文件需要在修改配置文件。

3. 如果引用了"js/jquery.mobile.min.js"，給form表單加上data-Ajax="false"，否則也收不到上傳的文件。

if (!Request.Content.IsMimeMultipartContent())            {                throw new HttPResponseException(HttpStatusCode.UnsupportedMediaType);            }            string root = @"C:/";            var provider = new MultipartFormDataStreamProvider(root);            try            {                StringBuilder sb = new StringBuilder();                var task = Request.Content.ReadAsMultipartAsync(provider);                task.Wait();                foreach (var file in provider.FileData)                {                    FileInfo fileInfo = new FileInfo(file.LocalFileName);                    sb.Append(string.Format("Uploaded file: {0} ({1} bytes)/n", fileInfo.Name, fileInfo.Length));                }                return new HttpResponseMessage()                {                    Content = new StringContent(sb.ToString())                };            }            catch (System.Exception e)            {                return Request.CreateErrorResponse(HttpStatusCode.InternalServerError, e);            }