private List<String> DirSearch(string sDir)
{
    List<String> files = new List<String>();
    try
    {
        foreach (string f in Directory.GetFiles(sDir))
        {
            files.Add(f);
        }
        foreach (string d in Directory.GetDirectories(sDir))
        {
            files.AddRange(DirSearch(d));
        }
    }
    catch (System.Exception excpt)
    {
        MessageBox.Show(excpt.Message);
    }

    return files;
}

如果您不想在内存中加载整个列表并避免阻塞，您可以查看以下答案.

and if you don't want to load the entire list in memory and avoid blocking you may take a look at the following answer.