asp.net分塊上傳大文件

轉自 http://blog.163.com/soldier_200/blog/static/1552123320091115319532/

sp.net分塊上傳大文件

1.一般的在Asp.net裏上傳文件都是10m左右，要做到大文件上傳，必須要改web.config,不過改了web.config有時候也上傳不成功，那是每次上傳的文件太大，瀏覽器在這個過程中會超時，採用分塊上傳的方法就可以避免這種情況。
2.分塊上傳就是利用post的方法，把數據分塊上傳，每塊上傳的數據量少，不會引起超時的問題。不說了，看代碼吧。
Code

using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using System.Reflection;
using System.Text;
using System.Web;

namespace Web
{
    //實現IHttpModule接口
    public class HttpUploadModule : IHttpModule
    {
        public HttpUploadModule() { }
        public void Dispose()
        {
        }

        public void Init(HttpApplication application)
        {
            //訂閱事件
            application.BeginRequest += new EventHandler(this.Application_BeginRequest);
        }

        private void Application_BeginRequest(object sender, EventArgs e)
        {
            HttpApplication app = sender as HttpApplication;
            HttpWorkerRequest request = GetWorkerRequest(app.Context);
            Encoding encoding = app.Context.Request.ContentEncoding;

            int bytesRead = 0; // 已讀數據大小
            int read;           // 當前讀取的塊的大小
            int count = 8192;   // 分塊大小
            byte[] buffer;      // 保存所有上傳的數據

            if (request != null)
            {
                // 返回 HTTP 請求正文已被讀取的部分。
                byte[] tempBuff = request.GetPreloadedEntityBody(); //要上傳的文件

                // 如果是附件上傳
                if (tempBuff != null && IsUploadRequest(app.Request))   //判斷是不是附件上傳
                {
                    // 獲取上傳大小
                    long length = long.Parse(request.GetKnownRequestHeader(HttpWorkerRequest.HeaderContentLength));

                    buffer = new byte[length];
                    count = tempBuff.Length; // 分塊大小

                    // 將已上傳數據複製過去
                    //
                    Buffer.BlockCopy(tempBuff, //源數據
                        0,                      //從0開始讀
                        buffer,                 //目標容器
                         bytesRead,              //指定存儲的開始位置
                         count);                 //要複製的字節數。 

                    // 開始記錄已上傳大小
                    bytesRead = tempBuff.Length;

                    // 循環分塊讀取，直到所有數據讀取結束
                    while (request.IsClientConnected() && !request.IsEntireEntityBodyIsPreloaded() && bytesRead < length)
                    {
                        // 如果最後一塊大小小於分塊大小，則重新分塊
                        if (bytesRead + count > length)
                        {
                            count = (int)(length - bytesRead);
                            tempBuff = new byte[count];
                        }
                        // 分塊讀取
                        read = request.ReadEntityBody(tempBuff, count);

                        // 複製已讀數據塊
                        Buffer.BlockCopy(tempBuff, 0, buffer, bytesRead, read);

                        // 記錄已上傳大小
                        bytesRead += read;
                    }

                    if (request.IsClientConnected() && !request.IsEntireEntityBodyIsPreloaded())
                    {
                        // 傳入已上傳完的數據
                        InjectTextParts(request, buffer);
                    }

                }
            }
        }

        HttpWorkerRequest GetWorkerRequest(HttpContext context)
        {
            IServiceProvider provider = (IServiceProvider)HttpContext.Current;
            return (HttpWorkerRequest)provider.GetService(typeof(HttpWorkerRequest));
        }

        /// <summary>
        /// 傳入已上傳完的數據
        /// </summary>
        /// <param name="request"></param>
        /// <param name="textParts"></param>
        void InjectTextParts(HttpWorkerRequest request, byte[] textParts)
        {
            BindingFlags bindingFlags = BindingFlags.Instance | BindingFlags.NonPublic;

            Type type = request.GetType();

            while ((type != null) && (type.FullName != "System.Web.Hosting.ISAPIWorkerRequest"))
            {
                type = type.BaseType;
            }

            if (type != null)
            {
                type.GetField("_contentAvailLength", bindingFlags).SetValue(request, textParts.Length);

                type.GetField("_contentTotalLength", bindingFlags).SetValue(request, textParts.Length);

                type.GetField("_preloadedContent", bindingFlags).SetValue(request, textParts);

                type.GetField("_preloadedContentRead", bindingFlags).SetValue(request, true);
            }

        }

        private static bool StringStartsWithAnotherIgnoreCase(string s1, string s2)
        {
            return (string.Compare(s1, 0, s2, 0, s2.Length, true, CultureInfo.InvariantCulture) == 0);
        }


        /// <summary>
        /// 是否爲附件上傳
        /// 判斷的根據是ContentType中有無multipart/form-data
        /// </summary>
        /// <param name="request"></param>
        /// <returns></returns>
        bool IsUploadRequest(HttpRequest request)
        {
            return StringStartsWithAnotherIgnoreCase(request.ContentType, "multipart/form-data");
        }

    }
}

3.用法
（1）修改web.config

  <system.web>
    <httpModules>
      <add type="HttpModelApp.HttpUploadModule, HttpModelApp" />
    </httpModules>
    <httpRuntime maxRequestLength="2000000"       executionTimeout="300" />
  </system.web>

(2)aspx

    <form runat="server" enctype="multipart/form-data" method="post">
        <div>
            <input type="file" runat="server"><br />
            <asp:Button runat="server" Text="上傳" /><br />
            <asp:Label runat="server"></asp:Label>
        </div>
    </form>

 (3)aspx.cs

        protected void Button1_Click(object sender, EventArgs e)
        {
            //要保存的位置
            string strDesPath = "D:\\";
            string strFileName = this.firstFile.PostedFile.FileName;
            strFileName = strDesPath + strFileName.Substring(strFileName.LastIndexOf("\\"));
            //
            this.firstFile.PostedFile.SaveAs(strFileName);
            this.Label1.Text = "文件保存到了：" + strFileName;
        }

4.大文件上傳的限制
雖然可以上傳大文件，但是這個大小也是有限制的，不能超過2G的大小。