关于c#异常

using System;
class mycount
{
static void Main(String[] args)
{
label:
Console.WriteLine("请输入x:");
double x = Convert.ToDouble(Console.ReadLine());
Console.WriteLine("请输入y:");
double y = Convert.ToDouble(Console.ReadLine());
Console.WriteLine("请选择运算类型:+，-，*，/");
string A = Console.ReadLine();
if (A == "+")
{
Console.WriteLine(x += y);

}
else if (A == "-")
{
Console.WriteLine(x -= y);
}
else if (A == "*")
{
Console.WriteLine(x *= y);

}
else if (A == "/")
{
Console.WriteLine(x /= y);

}
Console.WriteLine("是否进行新的运算:y/n");
string B = Co

具体的什么Exception我就不敢确定了：

using System;
class mycount
{
static void Main(String[] args)
{
int a=0;
double x=0;
double y = 0;
label:

Console.WriteLine("请输入x:");
while (a == 0)
{
try
{
x = Convert.ToDouble(Console.ReadLine());
a++;
}
catch (Exception e)
{
Console.WriteLine("请输入有效的x:");
}
}
Console.WriteLine("请输入y:");
while (a == 1)
{
try
{
y = Convert.ToDouble(Console.ReadLine());
a++;
}
catch (Exception e)
{
Console.WriteLine("请输入有效的y:");
}