一、前言
網上有許多的多線程斷點續傳操作，但總是寫的很云里霧里，或者寫的比較坑長。由于這幾個月要負責公司的在線升級項目，所以正好順便寫了一下
代碼如下：
using System;using System.Collections.Generic;using System.IO;using System.Threading.Tasks;namespace TestCenter{ class Program { static void Main(string[] args) { string LocalSavePath = @"E:/Test/TestFile/Local/1.msi"; //本地目標文件路徑 FileInfo SeverFilePath = new FileInfo(@"E:/Test/TestFile/Server/1.msi"); //服務器待文件路徑 long FileLength = SeverFilePath.Length; //待下載文件大小 Console.WriteLine("Start Configuration"); int PackCount = 0; //初始化數據包個數 long PackSize = 1024000; //數據包大小 if (FileLength % PackSize > 0) { PackCount = (int)(FileLength / PackSize) + 1; } else { PackCount = (int)(FileLength / PackSize); } Console.WriteLine("Start Recieve"); var tasks = new Task[PackCount]; //多線程任務 for (int index = 0; index < PackCount; index++) { int Threadindex = index; //這步很關鍵，在Task()里的絕對不能直接使用index var task = new Task(() => { string tempfilepath = @"E:/Test/TestFile/Temp/" + "QS_" + Threadindex + "_" + PackCount; //臨時文件路徑 using (FileStream tempstream = new FileStream(tempfilepath, FileMode.Create, FileAccess.Write, FileShare.Write)) { int length = (int)Math.Min(PackSize, FileLength - Threadindex * PackSize); var bytes = GetFile(Threadindex*PackCount, length); tempstream.Write(bytes, 0, length); tempstream.Flush(); tempstream.Close(); tempstream.Dispose(); } }); tasks[Threadindex] = task; task.Start(); } Task.WaitAll(tasks); //等待所有線程完成 Console.WriteLine("Recieve End"); //檢測有哪些數據包未下載 Console.WriteLine("Start Compare"); DirectoryInfo TempDir = new DirectoryInfo(@"E:/Test/TestFile/temp"); //臨時文件夾路徑 List<string> Comparefiles = new List<string>(); for (int i = 0; i < PackCount; i++) { bool hasfile = false; foreach (FileInfo Tempfile in TempDir.GetFiles()) { if (Tempfile.Name.Split('_')[1] == i.ToString()) { hasfile = true; break; } } if (hasfile == false) { Comparefiles.Add(i.ToString()); } } //最后補上這些缺失的文件 if (Comparefiles.Count > 0) { foreach (string com_index in Comparefiles) { string tempfilepath = @"E:/Test/TestFile/Temp/" + "QS_" + com_index+ "_" + PackCount; using (FileStream Compstream = new FileStream(tempfilepath, FileMode.Create, FileAccess.Write, FileShare.Write)) { int length = (int)Math.Min(PackSize, FileLength - Convert.ToInt32(com_index) * PackSize); var bytes = GetFile(Convert.ToInt32(com_index)*PackCount, length); Compstream.Write(bytes, 0, length); Compstream.Flush(); Compstream.Close(); Compstream.Dispose(); } } } Console.WriteLine("Compare End"); //準備將臨時文件融合并寫到1.msi中 Console.WriteLine("Start Write"); using (FileStream writestream = new FileStream(LocalSavePath, FileMode.Create, FileAccess.Write, FileShare.Write)) { foreach (FileInfo Tempfile in TempDir.GetFiles()) { using (FileStream readTempStream = new FileStream(Tempfile.FullName, FileMode.Open, FileAccess.Read, FileShare.ReadWrite)) { long onefileLength = Tempfile.Length; byte[] buffer = new byte[Convert.ToInt32(onefileLength)]; readTempStream.Read(buffer, 0, Convert.ToInt32(onefileLength)); writestream.Write(buffer, 0, Convert.ToInt32(onefileLength)); } } writestream.Flush(); writestream.Close(); writestream.Dispose(); } Console.WriteLine("Write End"); //刪除臨時文件 Console.WriteLine("Start Delete Temp Files"); foreach (FileInfo Tempfile in TempDir.GetFiles()) { Tempfile.Delete(); } Console.WriteLine("Delete Success"); Console.ReadKey(); } //這個方法可以放到Remoting或者WCF服務中去，然后本地調用該方法即可實現多線程斷點續傳 public static byte[] GetFile(int start, int length) { string SeverFilePath = @"E:/Test/TestFile/Server/1.msi"; using (FileStream ServerStream = new FileStream(SeverFilePath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite, 1024*80, true)) { byte[] buffer = new byte[length]; ServerStream.Position = start; //ServerStream.Seek(start, SeekOrigin.Begin); ServerStream.Read(buffer, 0, length); return buffer; } } }}二、討論
1）需要注意的是第44行，不能直接使用index變量在Task()里進行操作，而是要將它賦給Threadindex，讓Threadindex在Task()里，不然會直接報錯，為什么呢？查看鏈接
2）70至108行代碼可以在外面再套一層while循環，循環檢測臨時文件是否下完整了，然后再定義一個檢測最大上限，超過這個上限就放棄本次更新，當用戶的網絡恢復正常后下次再做更新操作。所以說放臨時文件的文件夾最好要包含版本信息，不會把2.0.0的臨時文件和1.0.0的臨時文件搞混。
3） FileStream.Position 與 FileStream.Seek(long offset, SeekOrigin seekorigin) 的作用都是獲取流的指針位置，當文件路徑使用絕對路徑時使用Position；相對路徑時使用Seek方法，查看鏈接
以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支持VEVB武林網。
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