当输入字母等非数字时，发生未经处理的异常，请问如何解决
比如怎样才能输入字母时，输出"输入错误!”
代码如下
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace ConsoleApplication1
{
class Program
{
static double San(double a, double b)
{
return a*b*0.5;
}
static double JuAndPing(double a, double b)
{
return a * b;
}
static double Yuan(double a)
{
return a * a * Math.PI;
}
static double Shan(double a, double b)
{
return a * b / 2;
}
static void Main(string[] args)
{
double x, y;
Console.WriteLine("****************");
Console.WriteLine(" 图形面积计算器 ");
Console.WriteLine("****************");
Console.WriteLine("1.三角形");
Console.WriteLine("2.矩形");
Console.WriteLine("3.圆形");
Console.WriteLine("4.扇形");
Console.WriteLine("5.平行四边形");
Console.WriteLine("请输入你的选择：");
int choice = Int32.Parse(Console.ReadLine());
switch (choice)
{
case 1:
Console.Write("请输入高：");
x = double.Parse(Console.ReadLine());
Console.Write("请输入边：");
y = double.Parse(Console.ReadLine());
Console.Write("三角形面积为：");
Console.WriteLine(San(x, y));
break;
case 2:
Console.Write("请输入长：");
x = double.Parse(Console.ReadLine());
Console.Write("请输入高：");
y = double.Parse(Console.ReadLine());
Console.Write("矩形面积为：");
Console.WriteLine(JuAndPing(x, y));
break;
case 3:
Console.Write("请输入半径：");
x = double.Parse(Console.ReadLine());
Console.Write("圆的面积为：");
Console.WriteLine(Yuan(x));
break;
case 4:
Console.Write("请输入半径：");
x = double.Parse(Console.ReadLine());
Console.Write("请输入弧长：");
y = double.Parse(Console.ReadLine());
Console.Write("扇形面积为：");
Console.WriteLine(Shan(x, y));
break;
case 5:
Console.Write("请输入底边：");
x = double.Parse(Console.ReadLine());
Console.Write("请输入高：");
y = double.Parse(Console.ReadLine());
Console.Write("平行四边形面积为：");
Console.WriteLine(JuAndPing(x, y));
break;
default: Console.WriteLine("输入错误，请输入1~5");
break;
}
}
}
}
------解决思路----------------------
bool isNum = false;
double x = 0.0;
Console.Write("请输入高：");
while (!isNum)
{
isNum = double.TryParse(Console.ReadLine(), out x);
if (isNum) break;
Console.Write("输入不正确，请再次输入高：");
}