bytes size c#

public static string GetSizeInMemory(this long bytesize)
{


    string[] sizes = { "B", "KB", "MB", "GB", "TB" };
    double len = Convert.ToDouble(bytesize);
    int order = 0;
    while(len >= 1024D && order < sizes.Length - 1)
    {
        order++;
        len /= 1024;
    }

    return string.Format(CultureInfo.CurrentCulture,"{0:0.##} {1}", len, sizes[order]);
}

  System.Text.ASCIIEncoding.Unicode.GetByteCount(string);
  System.Text.ASCIIEncoding.ASCII.GetByteCount(string);