/// <summary>
/// 全てのマスのうち、部屋かつすでにキャラクターがいない場所を取得
/// </summary>
/// <returns></returns>
public MapCell GetCharacterFreeCell()
{
return(MapData.Cast <MapCell>()
.Where(x => x.Terra == Enums.Terrain.Room && !Characters.Any(y => y.Position == x.Position))
.WaitedSample(x => 1));
}