获取指定类型的所有文件
public void GetAllFiles(DirectoryInfo dir, List<FileInfo> fileList,string extension=".png")
{
foreach (var item in dir.GetFiles())
{
if (string.IsNullOrEmpty(extension) || item.Extension.Equals(extension))
{
fileList.Add(item);
}
}
foreach (var item in dir.GetDirectories())
{
GetAllFiles(item, fileList,extension);
}
}