我遇到了一个小问题。我创建了一个程序，用户必须选择5个选项（1.输入数字2.显示最小3.显示最大4.显示所有数字5退出。） 所有选项均有效。问题是，当用户选择选项时，如果按任何字母都会给我错误。我希望如果用户按任何字母或任何符号作为警告消息，例如“输入的未知选项值”，然后重试。我想是关于转换或类似的东西，但我找不到问题所在。 这是我的代码：
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace Assignmen2014_15
{
class Program
{
const int MAXNUMBERS = 3;
static void Main(string[] args)
{
int[] theNumbers = new int[MAXNUMBERS];
int chosenOption = 0;
bool quit = false;
InitialiseNumbers(theNumbers);
while (quit == false)
{
DisplayHeader();
DisplayMenu();
chosenOption = ReadNumber("Please choose an option: ");
quit = ProcessMenu(chosenOption, theNumbers);
Console.Clear();
}
}
static void InitialiseNumbers(int[] numbers)
{
for (int index = 0; index < MAXNUMBERS; index++)
{
numbers[index] = 0;
}
}
static void DisplayHeader()
{
WriteText("*******************************************************************************", 0, 0); // Top left hand corner of screen is x = 0, y = 0;
WriteText("* This application is designed to allow you to choose numbers *", 0, 1); // Next line down is x = 0, y = 1, etc WriteText("* and finds the biggest and the smallest value *", 0, 2);
WriteText("*******************************************************************************", 0, 3);
}
static void DisplayMenu()
{
WriteText("Select an option", 20, 8); // Display menu at at x = 20, y = 8
WriteText("1. Enter the numbers", 20, 9);
WriteText("2. Find the smallest", 20, 10);
WriteText("3. Find the largest", 20, 11);
WriteText("4. Display all numbers", 20, 12);
WriteText("5. Quit", 20, 13);
}
static void WriteText(string text, int x, int y)
{
Console.CursorLeft = x;
Console.CursorTop = y;
Console.Write(text);
}
static int ReadNumber(string prompt)
{
string text;
int number;
WriteText(prompt, 20, 14);
text = Console.ReadLine();
number = int.Parse(text);
ClearText(20, 14, prompt.Length + text.Length); // Clear the text at this line
return number;
}
static void ClearText(int x, int y, int length)
{
// Write space ' ' characters starting at x, y for 'length' times
WriteText(new String(' ', length), x, y);
}
static void DisplayNumbers(int[] theNumbers)
{
Console.Write("Your numbers are: ");
for (int i = 0; i < MAXNUMBERS; i++)
{
Console.WriteLine(theNumbers[i]);
}
}
static bool ProcessMenu(int option, int[] numbers)
{
bool quit = false;
switch (option)
{
case 1:
GetNumbers(numbers);
break;
case 2:
WriteText(string.Format("The smallest value is {0}", FindSmallest(numbers)), 20, 15);
Console.ReadKey(); // Pause
break;
case 3:
WriteText(string.Format("The largest value is {0}", FindLargest(numbers)), 20, 15);
Console.ReadKey(); // Pause
break;
case 4:
DisplayNumbers(numbers);
Console.ReadKey();
break;
case 5:
quit = IsQuitting();
break;
default:
WriteText("Unknown option value entered", 20, 15);
Console.ReadKey(); // Pause
break;
}
return quit;
}
static void GetNumbers(int[] numbers)
{
for (int index = 0; index < MAXNUMBERS; index++)
{
numbers[index] = ReadNumber("Enter number: ");
}
}
static int FindSmallest(int[] numbers)
{
int smallest = numbers[0];
for (int index = 0; index < MAXNUMBERS - 1; index++) // <-- subtract 1
{
if (numbers[index + 1] < smallest)
{
smallest = numbers[index + 1];
}
}
return smallest;
}
static int FindLargest(int[] numbers)
{
int largest = numbers[0];
for (int index = 0; index < MAXNUMBERS - 1; index++) // <-- subtract 1
{
if (numbers[index + 1] > largest)
{
largest = numbers[index + 1];
}
}
return largest;
}
static bool IsQuitting()
{
string response;
bool quit = false;
WriteText("Do you really wish to quit? ", 20, 13);
response = Console.ReadLine();
if (response.Equals("Yes" , StringComparison.InvariantCultureIgnoreCase) || response.Equals("Y", StringComparison.InvariantCultureIgnoreCase))
{
quit = true;
}
return quit;
}
}
}
答案 0 :(得分：1)
使用Int32.TryParse(String, Int32)方法尝试将字符串解析为整数，并返回表示解析成功与否的布尔值。在您的情况下，如果解析失败，则可以从ReadNumber方法返回-1，该方法将调用您的切换情况的default:部分，并显示错误消息。否则，如果解析成功，则只需返回解析的数字，该数字将是您想要的数字之一，或者将调用default:操作。
String[] values = { null, "160519", "9432.0", "16,667",
" -322 ", "+4302", "(100);", "01FA" };
foreach (var value in values)
{
int number;
bool success = Int32.TryParse(value, out number);
if (success)
{
Console.WriteLine("Converted '{0}' to {1}.", value, number);
}
else
{
Console.WriteLine("Attempted conversion of '{0}' failed.",
value ?? "<null>");
}
}
在您的特定示例中，您需要修改ReadNumber(string prompt)方法：
static int ReadNumber(string prompt)
{
string text;
int number;
WriteText(prompt, 20, 14);
text = Console.ReadLine();
bool is_parsing_successful = Int32.TryParse(text, out number);
ClearText(20, 14, prompt.Length + text.Length); // Clear the text at this line
if(is_parsing_successful){
return number;
} else {
return -1;
}
}