c# 除掉前三个字符，剩下的4个字符全为数字方为特殊车辆

string plate="粤BN1223";

        if (plate.Contains("粤BN"))
            {
                //除掉前三个字符，剩下的4个字符全为数字方为特殊车辆 
                bool BNum = true;
                char[] strSubCCode = new char[4];

                if (plate.Length == 7)
                {
                    plate.CopyTo(3, strSubCCode, 0, 4);

                    foreach (char c in strSubCCode)
                    {
                        if (!Char.IsNumber(c))
                        {
                            BNum = false;
                            break;
                        }
                    }

                    if (BNum)
                    {
                        
                            Print.Log("特殊车辆:" + plate+ ",免费放行");

                    }
                }

            }