asp.net Web Api 上传文件

　　一、WebApi上使用MultipartFormDataStreamProvider来接收文件时，会自动将文件保存至指定目录下，文件名什么的都是自动生成的。代码如下：

[HttpPost, Route("savefiles")]
        public async Task<bool> SaveFile(string projectId, string eventId)
        {
            if (!Request.Content.IsMimeMultipartContent())
            {
                throw new HttpResponseException(HttpStatusCode.UnsupportedMediaType);
            } 
            string root = Path.Combine(HostingEnvironment.MapPath(ConfigurationManager.AppSettings["FileStorePath"]), DateTime.Now.ToShortDateString(), projectId);

            if (!Directory.Exists(root)) Directory.CreateDirectory(root);
            var provider = new MultipartFormDataStreamProvider(root);

            try
            {
                await Request.Content.ReadAsMultipartAsync(provider);
                
            }
            catch (Exception ex)
            {
                WebConfig.LoggerInstance.Error("上传文件出现异常：" + ex.Message);
            }
            return true;
        

然后在客户端调用如下代码即可

public async static Task<bool> UploadFile(string url, string fileName)
        {
            HttpClient httpClient = new HttpClient();

            var multipartContent = new MultipartFormDataContent();
            using (Stream stream = File.OpenRead(fileName))
            {
                multipartContent.Add(new StreamContent(stream), "test", "test.txt");

                var responseMessage = await httpClient.PostAsync(url, multipartContent);
                Task<string> body = responseMessage.Content.ReadAsStringAsync();
                if ("OK".Equals(responseMessage.StatusCode.ToString())) return true;
                else return false;
            }
        }

 二、自己保存文件

　　首先看下下面的uml 图，图中相关类为Microsoft默认提供的MIME处理类，最后的MultipartFormDataStreamProvider也在前篇博客中有介绍用法，如果要实现开发自定义如何保存文件，按个人最开始的想法是只要继承MultipartFormDataStreamProvider，并重载相关方法即可

实现代码如下

/// <summary>
    /// 与MultipartFormDataStreamProvider对应，但不将文件直接存入指定位置，而是需要自己指定数据流如何保存 
    /// </summary>
    public class MultipartFormDataMemoryStreamProvider : MultipartStreamProvider
    {
        private NameValueCollection _formData = new NameValueCollection();
        private Collection<bool> _isFormData = new Collection<bool>();

        /// <summary>  
        /// 获取文件对应的HttpContent集合,文件如何读取由实际使用方确定，可以ReadAsByteArrayAsync，也可以ReadAsStreamAsync  
        /// </summary>  
        public Collection<HttpContent> FileContents
        {
            get {
                if (this._isFormData.Count != this.Contents.Count)//两者总数不一致，认为未执行过必须的Request.Content.ReadAsMultipartAsync(provider)方法  
                {
                    throw new InvalidOperationException("System.Net.Http.HttpContentMultipartExtensions.ReadAsMultipartAsync must be called first!");
                }
                return new Collection<HttpContent>(this.Contents.Where((ct, idx) => !this._isFormData[idx]).ToList());
            }
        }

        public NameValueCollection FormData
        {
            get {
                return this._formData;
            }
        }
        public override async Task ExecutePostProcessingAsync()
        {
            for (var i = 0; i < this.Contents.Count; i++)
            {
                if (!this._isFormData[i])//非文件  
                {
                    continue;
                }
                var formContent = this.Contents[i];
                ContentDispositionHeaderValue contentDisposition = formContent.Headers.ContentDisposition;
                string formFieldName = UnquoteToken(contentDisposition.Name) ?? string.Empty;
                string formFieldValue = await formContent.ReadAsStringAsync();
                this.FormData.Add(formFieldName, formFieldValue);
            }
        }

        public override Stream GetStream(HttpContent parent, HttpContentHeaders headers)
        {
            if (parent == null)
            {
                throw new ArgumentNullException("parent");
            }
            if (headers == null)
            {
                throw new ArgumentNullException("headers");
            }
            ContentDispositionHeaderValue contentDisposition = headers.ContentDisposition;
            if (contentDisposition == null)
            {
                throw new InvalidOperationException("Content-Disposition is null");
            }
            this._isFormData.Add(string.IsNullOrEmpty(contentDisposition.FileName));
            return new MemoryStream();
        }

        /// <summary>  
        /// 复制自 System.Net.Http.FormattingUtilities 下同名方法，因为该类为internal，不能在其它命名空间下被调用  
        /// </summary>  
        /// <param name="token"></param>  
        /// <returns></returns>  
        private static string UnquoteToken(string token)
        {
            if (string.IsNullOrWhiteSpace(token))
            {
                return token;
            }
            if (token.StartsWith("\"", StringComparison.Ordinal) && token.EndsWith("\"", StringComparison.Ordinal) && token.Length > 1)
            {
                return token.Substring(1, token.Length - 2);
            }
            return token;
        }
    }

然后在在webapi端，使用 

var provider = new MultipartFormDataMemoryStreamProvider();

就可以了

 var provider = new MultipartFormDataMemoryStreamProvider();
            try
            {
                await Request.Content.ReadAsMultipartAsync(provider);
                foreach (var item in provider.Contents)
                {
                    var ms = item.ReadAsStreamAsync().Result;
                    using (var br = new BinaryReader(ms))
                    {
                        var data = br.ReadBytes((int)ms.Length);
                        File.WriteAllBytes(root + "/"+eventId+".txt", data);
                    }
                }
            }
            catch (Exception ex)
            {
                WebConfig.LoggerInstance.Error("上传文件出现异常：" + ex.Message);
            }