Move all files in subfolders to another folder using c#

private void MoveDirectory(string sourceDir, string targetDir, bool allowOverWriteFile)
{
    if (targetDir[targetDir.Length - 1] != Path.DirectorySeparatorChar)
    {
        targetDir += Path.DirectorySeparatorChar;
    }

    if (!Directory.Exists(targetDir))
    {
        Directory.CreateDirectory(targetDir);
    }

    string[] files = Directory.GetFileSystemEntries(sourceDir);
    foreach (string element in files)
    {
        // Sub directories
        if (Directory.Exists(element))
        {
            MoveDirectory(element, Path.Combine(targetDir, Path.GetFileName(element)), allowOverWriteFile);
        }
        // Files in directory
        else
        {
            File.Copy(element, Path.Combine(targetDir, Path.GetFileName(element)), allowOverWriteFile);
        }
    }
}