diff --git a/CHANGELOG.md b/CHANGELOG.md
index df7c3fb6..d156d45f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,13 @@
 ## CHANGE LOG
 
+
+### v6.1.1
+2014-02-25 issue [#41](https://github.com/qiniu/csharp-sdk/pull/41)
+
+- 简化断点续上传，删除bput逻辑
+- 增加断点续上传中块上传结果本地缓存特性
+- 修复bug：>2.5GB文件上传失败
+
 ### v6.1.0
 
 2014-02-18 issue [#37](https://github.com/qiniu/csharp-sdk/pull/37)
diff --git a/Docs/README.md b/Docs/README.md
index 70a011e5..a8944883 100644
--- a/Docs/README.md
+++ b/Docs/README.md
@@ -424,7 +424,7 @@ public static void PutFile(string bucket, string key, string fname)
 {
 	var policy = new PutPolicy(bucket, 3600);
 	string upToken = policy.Token();
-	PutExtra extra = new PutExtra { Bucket = bucket };
+	PutExtra extra = new PutExtra();
 	IOClient client = new IOClient();
 	client.PutFinished += new EventHandler<PutRet>((o, ret) => {
 		if (ret.OK)
diff --git a/Qiniu/IO/Resumable/ResumablePut.cs b/Qiniu/IO/Resumable/ResumablePut.cs
index 22893e0a..826df04b 100644
--- a/Qiniu/IO/Resumable/ResumablePut.cs
+++ b/Qiniu/IO/Resumable/ResumablePut.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.IO;
 using System.Text;
 #if NET40
@@ -64,16 +65,23 @@ public ResumablePutExtra Extra
             set { extra = value; }
         }
 
+        /// <summary>
+        /// Allow cache put result
+        /// </summary>
+        public bool AllowCache = true;
+
         /// <summary>
         /// 断点续传类
         /// </summary>
         /// <param name="putSetting"></param>
         /// <param name="extra"></param>
-        public ResumablePut(Settings putSetting, ResumablePutExtra extra)
+        /// <param name="allowcache">true:允许上传结果在本地保存，这样当网络失去连接而再次重新上传时，对已经上传成功的快不需要再次上传</param>
+        public ResumablePut(Settings putSetting, ResumablePutExtra extra,bool allowcache = true)
         {
             extra.chunkSize = putSetting.ChunkSize;
             this.putSetting = putSetting;
             this.extra = extra;
+            this.AllowCache = allowcache;
         }
 
         /// <summary>
@@ -88,6 +96,13 @@ public CallRet PutFile(string upToken, string localFile, string key)
             {
                 throw new Exception(string.Format("{0} does not exist", localFile));
             }
+            string puttedFile = string.Empty;
+            Dictionary<int, BlkputRet> puttedBlk = new Dictionary<int, BlkputRet>();
+            if (this.AllowCache)
+            {
+                puttedFile = ResumbalePutHelper.GetPutHistroryFile(localFile);
+                puttedBlk = ResumbalePutHelper.GetHistory(puttedFile);
+            }
             PutAuthClient client = new PutAuthClient(upToken);
             CallRet ret;
             using (FileStream fs = File.OpenRead(localFile))
@@ -97,26 +112,21 @@ public CallRet PutFile(string upToken, string localFile, string key)
                 chunks = fsize / extra.chunkSize + 1;
                 extra.Progresses = new BlkputRet[block_cnt];
                 //并行上传
-#if NET35||NET20
                 for (int i = 0; i < block_cnt; i++)
                 {
-#elif  NET40
-                Parallel.For(0, block_cnt, (i) =>{
-#endif
 
+                    if (this.AllowCache && puttedBlk != null && puttedBlk.ContainsKey(i) && puttedBlk[i] != null)
+                    {
+                        Console.WriteLine(string.Format("block{0} has putted", i));
+                        extra.Progresses[i] = puttedBlk[i];
+                        continue;
+                    }
                     int readLen = BLOCKSIZE;
-                    if ((i + 1) * BLOCKSIZE > fsize)
-                        readLen = (int)(fsize - i * BLOCKSIZE);
+                    if ((long)(i + 1) * BLOCKSIZE > fsize)
+                        readLen = (int)(fsize - (long)i * BLOCKSIZE);
                     byte[] byteBuf = new byte[readLen];
-#if NET40
-                    lock (fs)
-                    {
-#endif
-                    fs.Seek(i * BLOCKSIZE, SeekOrigin.Begin);
+                    fs.Seek((long)i * BLOCKSIZE, SeekOrigin.Begin);
                     fs.Read(byteBuf, 0, readLen);
-#if NET40
-                    }
-#endif
                     //并行上传BLOCK
                     BlkputRet blkRet = ResumableBlockPut(client, byteBuf, i, readLen);
                     if (blkRet == null)
@@ -125,13 +135,13 @@ public CallRet PutFile(string upToken, string localFile, string key)
                     }
                     else
                     {
+                        if (this.AllowCache)
+                        {
+                            ResumbalePutHelper.Append(puttedFile, i, blkRet);
+                        }
                         extra.OnNotify(new PutNotifyEvent(i, readLen, extra.Progresses[i]));
                     }
-#if NET35||NET20
                 }
-#elif NET40
-                    });
-#endif
                 ret = Mkfile(client, key, fs.Length);
             }
             if (ret.OK)
@@ -181,56 +191,41 @@ private BlkputRet ResumableBlockPut(Client client, byte[] body, int blkIdex, int
                 uint crc32 = CRC32.CheckSumBytes(firstChunk);
                 for (int i = 0; i < putSetting.TryTimes; i++)
                 {
-                    extra.Progresses[blkIdex] = Mkblock(client, firstChunk, body.Length);
-                    if (extra.Progresses[blkIdex] == null || crc32 != extra.Progresses[blkIdex].crc32)
+                    try
+                    {
+                        extra.Progresses[blkIdex] = Mkblock(client, firstChunk, body.Length);
+                    }
+                    catch (Exception ee)
                     {
                         if (i == (putSetting.TryTimes - 1))
                         {
-                            return null;
+                            throw ee;
                         }
+                        System.Threading.Thread.Sleep(1000);
                         continue;
                     }
-                    else
-                    {
-                        progress();
-                        break;
-                    }
-                }
-            }
-            #endregion
-
-            #region PutBlock
-            while (extra.Progresses[blkIdex].offset < blkSize)
-            {
-                bodyLength = (chunkSize < (blkSize - extra.Progresses[blkIdex].offset)) ? chunkSize : (int)(blkSize - extra.Progresses[blkIdex].offset);
-                byte[] chunk = new byte[bodyLength];
-                Array.Copy(body, extra.Progresses[blkIdex].offset, chunk, 0, bodyLength);
-                for (int i = 0; i < putSetting.TryTimes; i++)
-                {
-                    extra.Progresses[blkIdex] = BlockPut(client, extra.Progresses[blkIdex], new MemoryStream(chunk), bodyLength);
-                    if (extra.Progresses[blkIdex] == null)
+                    if (extra.Progresses[blkIdex] == null || crc32 != extra.Progresses[blkIdex].crc32)
                     {
                         if (i == (putSetting.TryTimes - 1))
                         {
                             return null;
                         }
+                        System.Threading.Thread.Sleep(1000);
                         continue;
                     }
                     else
                     {
-                        uploadedChunks++;
-                        if (Progress != null)
-                        {
-                            Progress((float)uploadedChunks / chunks);
-                        }
+                        progress();
                         break;
                     }
                 }
             }
             #endregion
+
             return extra.Progresses[blkIdex];
         }
 
+
         private BlkputRet Mkblock(Client client, byte[] firstChunk, long blkSize)
         {
             string url = string.Format("{0}/mkblk/{1}", Config.UP_HOST, blkSize);
@@ -242,17 +237,6 @@ private BlkputRet Mkblock(Client client, byte[] firstChunk, long blkSize)
             return null;
         }
 
-        private BlkputRet BlockPut(Client client, BlkputRet ret, Stream body, long length)
-        {
-            string url = string.Format("{0}/bput/{1}/{2}", Config.UP_HOST, ret.ctx, ret.offset);
-            CallRet callRet = client.CallWithBinary(url, "application/octet-stream", body, length);
-            if (callRet.OK)
-            {
-                return  QiniuJsonHelper.ToObject<BlkputRet>(callRet.Response);
-            }
-            return null;
-        }
-
         private CallRet Mkfile(Client client, string key, long fsize)
         {
             StringBuilder urlBuilder = new StringBuilder();
diff --git a/Qiniu/IO/Resumable/ResumablePutHelper.cs b/Qiniu/IO/Resumable/ResumablePutHelper.cs
new file mode 100644
index 00000000..20e2d5a9
--- /dev/null
+++ b/Qiniu/IO/Resumable/ResumablePutHelper.cs
@@ -0,0 +1,87 @@
+using System;
+using System.Collections.Generic;
+using System.Security.Cryptography;
+using System.IO;
+using System.IO.Compression;
+using Qiniu.IO.Resumable;
+namespace Qiniu
+{
+	public static class ResumbalePutHelper
+	{
+        public static Dictionary<int,BlkputRet> GetHistory(string filename)
+        {
+            return ParseHistory(filename);
+        }
+
+        /// <summary>
+        /// File Format:
+        /// i,offset,ctx/n
+        /// i,offset,ctx/n
+        /// </summary>
+        /// <param name="tempFile"></param>
+        public static Dictionary<int,BlkputRet> ParseHistory(string tempFile) 
+        {
+            if (!File.Exists(tempFile)) 
+            {
+                return null;
+            }
+            string[] lines = File.ReadAllLines(tempFile);
+            Dictionary<int, BlkputRet> result = new Dictionary<int, BlkputRet>();
+            foreach (string line in lines) 
+            {
+                string[] fields = line.Split(',');
+                BlkputRet ret = new BlkputRet();
+                ret.offset = ulong.Parse(fields[1]);
+                ret.ctx = fields[2];
+                int idx = int.Parse(fields[0]);
+                result.Add(idx, ret);
+            }
+            return result;
+        }
+
+        /// <summary>
+        /// 
+        /// </summary>
+        /// <param name="tempFileName"></param>
+        /// <param name="idx"></param>
+        /// <param name="ret"></param>
+        public static void Append(string tempFileName, int idx, BlkputRet ret)
+        {
+            string content = idx + "," + ret.offset + "," + ret.ctx + "\n";
+            File.AppendAllText(tempFileName, content);
+        }
+
+        /// <summary>
+        /// ��ȡ�ļ���SHA1ֵ
+        /// </summary>
+        /// <param name="filename"></param>
+        /// <returns>base64�����sha1ֵ</returns>
+        public static string GetFileBase64Sha1(string filename) 
+        {
+            SHA1 sha1 = new SHA1CryptoServiceProvider();
+            using (Stream reader = System.IO.File.OpenRead(filename))
+            {
+                byte[] result = sha1.ComputeHash(reader);
+                return BitConverter.ToString(result);
+            }
+        }
+
+        /// <summary>
+        /// ��ȡ��ʱ�ļ���
+        /// </summary>
+        /// <param name="filename"></param>
+        /// <returns></returns>
+        public static string GetTempleFile(string filename)
+        {
+            string tempPath = Path.GetTempPath();
+            return tempPath + filename;
+        } 
+
+        public static string GetPutHistroryFile(string filename) { 
+
+            string f = GetFileBase64Sha1(filename);
+            return GetTempleFile(f);
+        }
+	}
+}
+
diff --git a/Qiniu/IO/Resumable/ResumablePutRet.cs b/Qiniu/IO/Resumable/ResumablePutRet.cs
index e7dfa6d0..a04828e2 100644
--- a/Qiniu/IO/Resumable/ResumablePutRet.cs
+++ b/Qiniu/IO/Resumable/ResumablePutRet.cs
@@ -13,6 +13,6 @@ public class BlkputRet
 		[JsonProperty("crc32")]
 		public UInt32 crc32;
 		[JsonProperty("offset")]
-		public UInt32 offset;
+		public ulong offset;
 	}
 }
diff --git a/Qiniu/IO/Resumable/Settings.cs b/Qiniu/IO/Resumable/Settings.cs
index 63331210..4c98e784 100644
--- a/Qiniu/IO/Resumable/Settings.cs
+++ b/Qiniu/IO/Resumable/Settings.cs
@@ -32,8 +32,9 @@ public int TryTimes {
 		/// <param name="chunkSize">chunk大小,默认为4MB</param>
 		/// <param name="tryTimes">失败重试次数,默认为3</param>
 		public Settings (int chunkSize=1 << 22, int tryTimes=3)
-		{
-			this.chunkSize = chunkSize;
+		{
+            //取消chunk
+            this.chunkSize = 1 << 22;
 			this.tryTimes = tryTimes; 
 		}
 	}
diff --git a/Qiniu/Qiniu.2.0.csproj b/Qiniu/Qiniu.2.0.csproj
index 00539836..b5e9df3e 100644
--- a/Qiniu/Qiniu.2.0.csproj
+++ b/Qiniu/Qiniu.2.0.csproj
@@ -15,7 +15,7 @@
     <TargetFrameworkProfile />
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|x86' ">
-    <PlatformTarget>x86</PlatformTarget>
+    <PlatformTarget>AnyCPU</PlatformTarget>
     <DebugSymbols>true</DebugSymbols>
     <DebugType>full</DebugType>
     <Optimize>false</Optimize>
@@ -53,6 +53,7 @@
     <Compile Include="IO\PutExtra.cs" />
     <Compile Include="IO\PutRet.cs" />
     <Compile Include="IO\Resumable\ResumablePutExtra.cs" />
+    <Compile Include="IO\Resumable\ResumablePutHelper.cs" />
     <Compile Include="IO\Resumable\Settings.cs" />
     <Compile Include="RS\GetPolicy.cs" />
     <Compile Include="RS\PutPolicy.cs" />
diff --git a/Qiniu/Qiniu.4.0.csproj b/Qiniu/Qiniu.4.0.csproj
index 1734a9af..43ffa972 100644
--- a/Qiniu/Qiniu.4.0.csproj
+++ b/Qiniu/Qiniu.4.0.csproj
@@ -15,7 +15,7 @@
     <TargetFrameworkProfile />
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|x86' ">
-    <PlatformTarget>x86</PlatformTarget>
+    <PlatformTarget>AnyCPU</PlatformTarget>
     <DebugSymbols>true</DebugSymbols>
     <DebugType>full</DebugType>
     <Optimize>false</Optimize>
@@ -53,6 +53,7 @@
     <Compile Include="IO\PutExtra.cs" />
     <Compile Include="IO\PutRet.cs" />
     <Compile Include="IO\Resumable\ResumablePutExtra.cs" />
+    <Compile Include="IO\Resumable\ResumablePutHelper.cs" />
     <Compile Include="IO\Resumable\Settings.cs" />
     <Compile Include="RS\GetPolicy.cs" />
     <Compile Include="RS\PutPolicy.cs" />
@@ -102,4 +103,4 @@
     <None Include="app.config" />
   </ItemGroup>
   <ItemGroup />
-</Project>
+</Project>
\ No newline at end of file
diff --git a/bin/Qiniu.2.0.dll b/bin/Qiniu.2.0.dll
new file mode 100755
index 00000000..aa4d0d98
Binary files /dev/null and b/bin/Qiniu.2.0.dll differ
diff --git a/bin/Qiniu.4.0.dll b/bin/Qiniu.4.0.dll
index 3263456b..dc9d0294 100755
Binary files a/bin/Qiniu.4.0.dll and b/bin/Qiniu.4.0.dll differ
diff --git a/csharp-sdk.2.0.sln b/csharp-sdk.2.0.sln
index f374e292..d3f062ea 100644
--- a/csharp-sdk.2.0.sln
+++ b/csharp-sdk.2.0.sln
@@ -3,9 +3,9 @@ Microsoft Visual Studio Solution File, Format Version 11.00
 # Visual Studio 2010
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "SDK", "SDK", "{65603FA4-DDC3-4FD7-ADA3-7BCC2161A247}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Qiniu", "Qiniu\Qiniu.2.0.csproj", "{AD4EA9D1-11C2-4BF6-8A06-72A966BC1B80}"
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Qiniu.2.0", "Qiniu\Qiniu.2.0.csproj", "{AD4EA9D1-11C2-4BF6-8A06-72A966BC1B80}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Qiniu.Test", "Qiniu.Test\Qiniu.2.0.Test.csproj", "{95DC2A77-2344-4315-9F6F-334CC928459C}"
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Qiniu.2.0.Test", "Qiniu.Test\Qiniu.2.0.Test.csproj", "{95DC2A77-2344-4315-9F6F-334CC928459C}"
 EndProject
 Global
 	GlobalSection(TestCaseManagementSettings) = postSolution
diff --git a/csharp-sdk.4.0.sln b/csharp-sdk.4.0.sln
index a98455bc..7d25e03f 100644
--- a/csharp-sdk.4.0.sln
+++ b/csharp-sdk.4.0.sln
@@ -3,9 +3,9 @@ Microsoft Visual Studio Solution File, Format Version 11.00
 # Visual Studio 2010
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "SDK", "SDK", "{65603FA4-DDC3-4FD7-ADA3-7BCC2161A247}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Qiniu", "Qiniu\Qiniu.4.0.csproj", "{AD4EA9D1-11C2-4BF6-8A06-72A966BC1B80}"
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Qiniu.4.0", "Qiniu\Qiniu.4.0.csproj", "{AD4EA9D1-11C2-4BF6-8A06-72A966BC1B80}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Qiniu.Test", "Qiniu.Test\Qiniu.4.0.Test.csproj", "{95DC2A77-2344-4315-9F6F-334CC928459C}"
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Qiniu.4.0.Test", "Qiniu.Test\Qiniu.4.0.Test.csproj", "{95DC2A77-2344-4315-9F6F-334CC928459C}"
 EndProject
 Global
 	GlobalSection(TestCaseManagementSettings) = postSolution