利用if else 判断方程有几个根

static void Main(string[] args)
        {
             Console.ForegroundColor = ConsoleColor.Green;
            Console.Clear();
            while (true)
            {

                Console.WriteLine("求方程式ax²+bx=c=0的根的情况");
                double a, b, c, d; string e;
                Console.WriteLine("请输入a：");
                a = Convert.ToDouble(Console.ReadLine());
                Console.WriteLine("请输入b：");
                b = Convert.ToDouble(Console.ReadLine());
                Console.WriteLine("请输入c：");
                c = Convert.ToDouble(Console.ReadLine());
                if (a > 0||a<0)
                {
                    Console.WriteLine("方程为一元二次方程");

                    d = b * b - 4 * a * c;
                    Console.WriteLine("形成的德尔塔为" + d);
                    if (d > 0)
                    {
                        Console.WriteLine("方程有两个根");
                    }
                    else if (d == 0)
                    {
                        Console.WriteLine("方程有一个根");
                    }
                    else
                    {
                        Console.WriteLine("方程无解");

                    }

                }
                else
                {
                    Console.WriteLine("方程不是一元二次方程");
                }

                Console.ReadLine();

            }
        }
    }