这里有一个简洁而有效的解决方案:

namespace System.IO {
  public static class ExtensionMethods {

    public static void CopyTo(this DirectoryInfo srcPath, string destPath) {
      Directory.CreateDirectory(destPath);
      Parallel.ForEach(srcPath.GetDirectories("*", SearchOption.AllDirectories), 
        srcInfo => Directory.CreateDirectory($"{destPath}{srcInfo.FullName[srcPath.FullName.Length..]}"));
      Parallel.ForEach(srcPath.GetFiles("*", SearchOption.AllDirectories), 
        srcInfo => File.Copy(srcInfo.FullName, $"{destPath}{srcInfo.FullName[srcPath.FullName.Length..]}", true));
      });
    }

  }
}

使用方法:

new DirectoryInfo(sourcePath).CopyTo(destinationPath);

下面是一个DirectoryInfo的扩展方法。CopyTo(注意overwrite参数):

public static DirectoryInfo CopyTo(this DirectoryInfo sourceDir, string destinationPath, bool overwrite = false)
{
    var sourcePath = sourceDir.FullName;

    var destination = new DirectoryInfo(destinationPath);

    destination.Create();

    foreach (var sourceSubDirPath in Directory.EnumerateDirectories(sourcePath, "*", SearchOption.AllDirectories))
        Directory.CreateDirectory(sourceSubDirPath.Replace(sourcePath, destinationPath));

    foreach (var file in Directory.EnumerateFiles(sourcePath, "*", SearchOption.AllDirectories))
        File.Copy(file, file.Replace(sourcePath, destinationPath), overwrite);

    return destination;
}

下面是我用于IO任务的一个实用程序类。

using System;
using System.Runtime.InteropServices;

namespace MyNameSpace
{
    public class ShellFileOperation
    {
        private static String StringArrayToMultiString(String[] stringArray)
        {
            String multiString = "";

            if (stringArray == null)
                return "";

            for (int i=0 ; i<stringArray.Length ; i++)
                multiString += stringArray[i] + '\0';

            multiString += '\0';

            return multiString;
        }

        public static bool Copy(string source, string dest)
        {
            return Copy(new String[] { source }, new String[] { dest });
        }

        public static bool Copy(String[] source, String[] dest)
        {
            Win32.SHFILEOPSTRUCT FileOpStruct = new Win32.SHFILEOPSTRUCT();

            FileOpStruct.hwnd = IntPtr.Zero;
            FileOpStruct.wFunc = (uint)Win32.FO_COPY;

            String multiSource = StringArrayToMultiString(source);
            String multiDest = StringArrayToMultiString(dest);
            FileOpStruct.pFrom = Marshal.StringToHGlobalUni(multiSource);
            FileOpStruct.pTo = Marshal.StringToHGlobalUni(multiDest);

            FileOpStruct.fFlags = (ushort)Win32.ShellFileOperationFlags.FOF_NOCONFIRMATION;
            FileOpStruct.lpszProgressTitle = "";
            FileOpStruct.fAnyOperationsAborted = 0;
            FileOpStruct.hNameMappings = IntPtr.Zero;

            int retval = Win32.SHFileOperation(ref FileOpStruct);

            if(retval != 0) return false;
            return true;
        }

        public static bool Move(string source, string dest)
        {
            return Move(new String[] { source }, new String[] { dest });
        }

        public static bool Delete(string file)
        {
            Win32.SHFILEOPSTRUCT FileOpStruct = new Win32.SHFILEOPSTRUCT();

            FileOpStruct.hwnd = IntPtr.Zero;
            FileOpStruct.wFunc = (uint)Win32.FO_DELETE;

            String multiSource = StringArrayToMultiString(new string[] { file });
            FileOpStruct.pFrom = Marshal.StringToHGlobalUni(multiSource);
            FileOpStruct.pTo =  IntPtr.Zero;

            FileOpStruct.fFlags = (ushort)Win32.ShellFileOperationFlags.FOF_SILENT | (ushort)Win32.ShellFileOperationFlags.FOF_NOCONFIRMATION | (ushort)Win32.ShellFileOperationFlags.FOF_NOERRORUI | (ushort)Win32.ShellFileOperationFlags.FOF_NOCONFIRMMKDIR;
            FileOpStruct.lpszProgressTitle = "";
            FileOpStruct.fAnyOperationsAborted = 0;
            FileOpStruct.hNameMappings = IntPtr.Zero;

            int retval = Win32.SHFileOperation(ref FileOpStruct);

            if(retval != 0) return false;
            return true;
        }

        public static bool Move(String[] source, String[] dest)
        {
            Win32.SHFILEOPSTRUCT FileOpStruct = new Win32.SHFILEOPSTRUCT();

            FileOpStruct.hwnd = IntPtr.Zero;
            FileOpStruct.wFunc = (uint)Win32.FO_MOVE;

            String multiSource = StringArrayToMultiString(source);
            String multiDest = StringArrayToMultiString(dest);
            FileOpStruct.pFrom = Marshal.StringToHGlobalUni(multiSource);
            FileOpStruct.pTo = Marshal.StringToHGlobalUni(multiDest);

            FileOpStruct.fFlags = (ushort)Win32.ShellFileOperationFlags.FOF_NOCONFIRMATION;
            FileOpStruct.lpszProgressTitle = "";
            FileOpStruct.fAnyOperationsAborted = 0;
            FileOpStruct.hNameMappings = IntPtr.Zero;

            int retval = Win32.SHFileOperation(ref FileOpStruct);

            if(retval != 0) return false;
            return true;
        }
    }
}

一个只有一个循环复制所有文件夹和文件的变体:

foreach (var f in Directory.GetFileSystemEntries(path, "*", SearchOption.AllDirectories))
{
    var output = Regex.Replace(f, @"^" + path, newPath);
    if (File.Exists(f)) File.Copy(f, output, true);
    else Directory.CreateDirectory(output);
}

复制并替换文件夹中的所有文件

        public static void CopyAndReplaceAll(string SourcePath, string DestinationPath, string backupPath)
    {
            foreach (string dirPath in Directory.GetDirectories(SourcePath, "*", SearchOption.AllDirectories))
            {
                Directory.CreateDirectory($"{DestinationPath}{dirPath.Remove(0, SourcePath.Length)}");
                Directory.CreateDirectory($"{backupPath}{dirPath.Remove(0, SourcePath.Length)}");
            }
            foreach (string newPath in Directory.GetFiles(SourcePath, "*.*", SearchOption.AllDirectories))
            {
                if (!File.Exists($"{ DestinationPath}{newPath.Remove(0, SourcePath.Length)}"))
                    File.Copy(newPath, $"{ DestinationPath}{newPath.Remove(0, SourcePath.Length)}");
                else
                    File.Replace(newPath
                        , $"{ DestinationPath}{newPath.Remove(0, SourcePath.Length)}"
                        , $"{ backupPath}{newPath.Remove(0, SourcePath.Length)}", false);
            }
    }

它可能没有性能意识，但我用它来处理30MB的文件夹，它工作得完美无缺。另外，我不喜欢这么简单的任务所需要的大量代码和递归。

var src = "c:\src";
var dest = "c:\dest";
var cmp = CompressionLevel.NoCompression;
var zip = source_folder + ".zip";

ZipFile.CreateFromDirectory(src, zip, cmp, includeBaseDirectory: false);
ZipFile.ExtractToDirectory(zip, dest_folder);

File.Delete(zip);

注意:ZipFile可以在。net 4.5+的System.IO.Compression命名空间中使用