C#检查标准图幅编号

/// <summary>
/// 检查是否为标准图幅编号
/// </summary>
/// <param name="MapNumber">图幅编号</param>
/// <returns>检查结果True/false</returns>
private bool CheckMapNumber(string MapNumber)
{
    int ColumnNumber100;
    if (MapNumber.Length == 3)//1:100万图幅规则
    {
        Regex RegMapNumber = new Regex(@"^[A-S]\d\d$");
        if (RegMapNumber.IsMatch(MapNumber.ToUpper()))
        {
            ColumnNumber100 = Convert.ToInt32(MapNumber.Substring(1, 2));
            if (ColumnNumber100 <= 60)
            { return true; }
        }
    }
    if (MapNumber.Length == 10)//其他图幅规则
    {
        string ScaleMark = "";
        int ColumnNumber;
        int RowNumber;
        int RowMax = 0;
        int ColumnMax = 0;
        Regex RegMapNumber = new Regex(@"^[A-S]\d\d[B-H]\d\d\d\d\d\d$");
        if (RegMapNumber.IsMatch(MapNumber.ToUpper()))
        {
            ScaleMark = MapNumber.Substring(3, 1);
            switch(ScaleMark)
            {
                case "B":
                    RowMax = 2;
                    ColumnMax = 2;
                    break;
                case "C":
                    RowMax = 4;
                    ColumnMax = 4;
                    break;
                case "D":
                    RowMax = 12;
                    ColumnMax = 12;
                    break;
                case "E":
                    RowMax = 24;
                    ColumnMax = 24;
                    break;
                case "F":
                    RowMax = 48;
                    ColumnMax = 48;
                    break;
                case "G":
                    RowMax = 96;
                    ColumnMax = 96;
                    break;
                case "H":
                    RowMax = 192;
                    ColumnMax = 192;
                    break;
                default:
                    RowMax = 0;
                    ColumnMax = 0;
                    break;
            }
            ColumnNumber100 = Convert.ToInt32(MapNumber.Substring(1, 2));
            RowNumber = Convert.ToInt32(MapNumber.Substring(4, 3));
            ColumnNumber = Convert.ToInt32(MapNumber.Substring(7, 3));
            if (ColumnNumber100 <= 60 && RowNumber <= RowMax && ColumnNumber <= ColumnMax)
            { return true; }
        }
    }
    return false;
}