尝试了两种方法，通过不同的dll体现

一、using Ionic.Zip;

优点：简单明了。缺点：android上无法解压,ios未尝试

代码：

//解压到指定目录
using(ZipFile zip = new ZipFile(path1 + "/"+FileName+".zip"))
{
zip.ExtractAll(path2);
// for(int i=0;i<zip.Count;i++){
// zip[i].Extract(path1);
// }  
}

二、using ICSharpCode.SharpZipLib.Zip;

优点：支持android，ios未尝试。缺点：遍历所有子文件，解压速度略慢

代码：

public void UnpackFiles(string file, string dir)
{
try
  {
   if (!Directory.Exists(dir))
    Directory.CreateDirectory(dir);

    ZipInputStream s = new ZipInputStream(File.OpenRead(file));
    ZipEntry theEntry;
  while ((theEntry = s.GetNextEntry()) != null)
  {
   string directoryName = Path.GetDirectoryName(theEntry.Name);
   string fileName = Path.GetFileName(theEntry.Name);
   if (directoryName != String.Empty)
      Directory.CreateDirectory(dir + directoryName);

    if (fileName != String.Empty)
    {
      FileStream streamWriter = File.Create(dir + theEntry.Name);
int size = 2048;
byte[] data = new byte[2048];
       while (true)
      {
size = s.Read(data, 0, data.Length);
if (size > 0)
{
streamWriter.Write(data, 0, size);
}
else
{
break;
}
      }
      streamWriter.Close();
    }
}
s.Close();
  }catch (Exception)
  {
    throw;
  }
}