使用带有枚举C#的Switch语句
本文关键字：Switch 语句 枚举 | 更新日期: 2023-09-27 18:24:05
嗨，我正在创建一个控制台应用程序，用户在其中输入一个月的数字，应用程序计算出它是哪个月，并显示答案和一个月中的天数。当switch语句在Main方法中时，我就让它工作了，但现在它显示错误的月份。我有以下代码：
namespace ConsoleCA2{
public enum Months
{
January = 31,
February = 28,
March = 31,
April = 30,
May = 31,
June = 30,
July = 31,
August = 31,
September = 30,
October = 31,
November = 30,
December = 31
};
public class Program
{
public const string NEWLINE = "'n"; //constant for new line
static void Main(string[] args)
{
try
{
//prompt user for month number.
Console.Write("Enter a Number to find out what Month it is: ");
//convert users answer to integer
int userInput = Convert.ToInt16(Console.ReadLine());
//declare and initalise
int daysInMonth = 0;
string answer = String.Empty;
//call relevent calculation methods
answer = DetermineMonth(userInput);
daysInMonth = DetermineDaysInMonth(userInput);
//Write users answer to screen
Console.WriteLine(answer);
//Prompt user, whether they want to know number of days in the
//month
Console.Write("Would you like to know the number of days in" +
" {0}: ", answer);
//assign users answer to variable
string userAnswer = Console.ReadLine();
//Output answer if needed.
if (userAnswer == "yes".Trim().ToLower())
{
Console.WriteLine("The number of days in {0} is: {1}",
answer, daysInMonth.ToString());
}
else if (userAnswer == "no".Trim().ToLower())
{
Console.WriteLine(NEWLINE);
Console.WriteLine("You answered No, Have a good day!");
}
else
{
Console.WriteLine("Please answer yes or no.");
}
Console.Read(); //Pauses screen for user
}
//catch any errors.
catch (Exception err)
{
Console.WriteLine("Error" + err.Message);
}
}
/// <summary>
/// Determines What month the use enters and returns string value
/// </summary>
/// <param name="userInput"></param>
/// <returns>returns the month as string</returns>
public static String DetermineMonth(int userInput)
{
switch (userInput)
{
case 1:
return Months.January.ToString();
case 2:
return Months.February.ToString();
case 3:
return Months.March.ToString();
case 4:
return Months.April.ToString();
case 5:
return Months.May.ToString();
case 6:
return Months.June.ToString();
case 7:
return Months.July.ToString();
case 8:
return Months.August.ToString();
case 9:
return Months.September.ToString();
case 10:
return Months.October.ToString();
case 11:
return Months.November.ToString();
case 12:
return Months.December.ToString();
default:
return "Error";
}
}
/// <summary>
/// Determines how many days is in selected month as integer
/// </summary>
/// <param name="userInput"></param>
/// <returns>returns how many days in month</returns>
public static int DetermineDaysInMonth(int userInput)
{
switch (userInput)
{
case 1:
return Convert.ToInt16(Months.January);
case 2:
return Convert.ToInt16(Months.February);
case 3:
return Convert.ToInt16(Months.March);
case 4:
return Convert.ToInt16(Months.April);
case 5:
return Convert.ToInt16(Months.May);
case 6:
return Convert.ToInt16(Months.June);
case 7:
return Convert.ToInt16(Months.July);
case 8:
return Convert.ToInt16(Months.August);
case 9:
return Convert.ToInt16(Months.September);
case 10:
return Convert.ToInt16(Months.October);
case 11:
return Convert.ToInt16(Months.November);
case 12:
return Convert.ToInt16(Months.December);
default:
return 0;
}
}
旧的switch语句是这样的：
switch (userInput)
{
case 1:
answer = Months.January.ToString();
daysInMonth = Convert.ToInt16(Months.January);
break;
case 2:
answer = Months.February.ToString();
daysInMonth = Convert.ToInt16(Months.February);
break;
case 3:
answer = Months.March.ToString();
daysInMonth = Convert.ToInt16(Months.March);
break;
case 4:
answer = Months.April.ToString();
daysInMonth = Convert.ToInt16(Months.April);
break;
case 5:
answer = Months.May.ToString();
daysInMonth = Convert.ToInt16(Months.May);
break;
case 6:
answer = Months.June.ToString();
daysInMonth = Convert.ToInt16(Months.June);
break;
case 7:
answer = Months.July.ToString();
daysInMonth = Convert.ToInt16(Months.July);
break;
case 8:
answer = Months.August.ToString();
daysInMonth = Convert.ToInt16(Months.August);
break;
case 9:
answer = Months.September.ToString();
daysInMonth = Convert.ToInt16(Months.September);
break;
case 10:
answer = Months.October.ToString();
daysInMonth = Convert.ToInt16(Months.October);
break;
case 11:
answer = Months.November.ToString();
daysInMonth = Convert.ToInt16(Months.November);
break;
case 12:
answer = Months.December.ToString();
daysInMonth = Convert.ToInt16(Months.December);
break;
default:
answer = "Error";
break;
}
这一直有效，直到我改为单独的方法，然后它就走下坡路了。现在，即使我把它放回去，它仍然会把几个月搞混？
如此困惑：S
提前感谢您的帮助。。。如果你能理解混乱的代码：p
NET框架包含大量的代码。有时很难找到所需的，但已经有东西的可能性很高。而且，虽然搜索需要时间，但这是一段很好的时间，因为你为自己未来的工作提供了有用的知识
CultureInfo.CurrentCulture.DayFormatInfo.MonthNames
日期时间日期当月
using System.Globalization;
static void Main(string[] args)
{
Console.Write("Enter a Number to find out what Month it is: ");
int userInput = Convert.ToInt16(Console.ReadLine());
if(userInput > 0 && userInput < 13)
{
string monthName = CultureInfo.CurrentCulture.DayTimeFormat.MonthNames[userInput-1];
int daysInMonth = DateTime.DaysInMonth(2013, userInput);
......
}
}
如果你还需要计算闰年，你应该得到年份的输入，但非常简单
使用enum为常量创建符号名称。在这种情况下，这不是你想要的。
我认为你想要的是一个查找表，给定值a，返回值B。在你的情况下，你可以使用几个数组：
string[] monthNames = new string[]
{
"January", "February", "March", "April", "May", "June",
"July", "August", "September", "November", "December"
};
int[] monthDays = new int[] {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
然后，您可以通过查找获得月份名称和天数：
int userInput = Convert.ToInt16(Console.ReadLine());
if (userInput < 1 || userInput > 12)
Console.WriteLine("Error: invalid month.");
else
{
answer = monthNames[userInput-1];
daysInMonth = monthDays[userInput-1];
}
还有其他方法可以做到这一点，包括在几个月或几天内使用structs或类，但这些都是稍微高级一些的主题。
此外，.NET有一个DateTime结构，它具有所有这些功能以及更多用于处理日期和时间的功能。在生产程序中，你应该使用它，而不是自己滚动。
这是因为您的枚举将所有内容混合在一起。
31和30存在重复值。
下面是一个工作示例（不过还有更多的优化方法。比如使用DateTime类）
public enum Months : int
{
None = 0,
January = 1,
February = 2,
March = 3,
April = 4,
May = 5,
June = 6,
July = 7,
August = 8,
September = 9,
October = 10,
November = 11,
December = 12
};
public class Program
{
public const string NEWLINE = "'n"; //constant for new line
static void Main(string[] args)
{
try
{
//prompt user for month number.
Console.Write("Enter a Number to find out what Month it is: ");
//convert users answer to integer
int userInput = Convert.ToInt16(Console.ReadLine());
//declare and initalise
int daysInMonth = 0;
Months answer;
//call relevent calculation methods
answer = DetermineMonth(userInput);
if (answer == Months.None)
{
Console.WriteLine("Please enter a value between 1 and 12");
return;
}
daysInMonth = DetermineDaysInMonth(answer);
//Write users answer to screen
Console.WriteLine(answer);
//Prompt user, whether they want to know number of days in the
//month
Console.Write("Would you like to know the number of days in {0}: ", answer);
//assign users answer to variable
string userAnswer = Console.ReadLine();
//Output answer if needed.
if (userAnswer == "yes".Trim().ToLower())
{
Console.WriteLine("The number of days in {0} is: {1}", answer, daysInMonth.ToString());
}
else if (userAnswer == "no".Trim().ToLower())
{
Console.WriteLine(NEWLINE);
Console.WriteLine("You answered No, Have a good day!");
}
else
Console.WriteLine("Please answer yes or no.");
Console.ReadLine(); //Pauses screen for user
}
//catch any errors.
catch (Exception err)
{
Console.WriteLine("Error" + err.Message);
}
}
/// <summary>
/// Determines What month the use enters and returns string value
/// </summary>
/// <param name="userInput"></param>
/// <returns>returns the month as string</returns>
public static Months DetermineMonth(int userInput)
{
switch (userInput)
{
case 1:
return Months.January;
case 2:
return Months.February;
case 3:
return Months.March;
case 4:
return Months.April;
case 5:
return Months.May;
case 6:
return Months.June;
case 7:
return Months.July;
case 8:
return Months.August;
case 9:
return Months.September;
case 10:
return Months.October;
case 11:
return Months.November;
case 12:
return Months.December;
}
return Months.None;
}
/// <summary>
/// Determines how many days is in selected month as integer
/// </summary>
/// <param name="userInput"></param>
/// <returns>returns how many days in month</returns>
public static int DetermineDaysInMonth(Months userInput)
{
switch (Convert.ToInt32(userInput))
{
case 1:
case 3:
case 5:
case 7:
case 8:
case 10:
case 12:
return 31;
case 2:
return 28;
case 4:
case 6:
case 9:
case 11:
return 30;
}
return 0;
}
}
您可能需要考虑将其简化一点，并使您的枚举数与月份数相匹配。然后将当月的天数存储到其他地方。
然后，您可以使用（Months）userInput来获取枚举并消除至少一个switch语句。
您可以使用Dictionary或其他方式存储每个月的天数，只要枚举为每个值存储一个唯一的int即可。
这不是使用枚举的方式。
它们不仅仅是静态键值对：如果是，那么您可以使用的不仅仅是积分类型。不，它们只不过是围绕整型的类型安全包装器。
你的问题是：
public enum Months
{
January = 31,
February = 28,
March = 31,
April = 30,
May = 31,
June = 30,
July = 31,
August = 31,
September = 30,
October = 31,
November = 30,
December = 31
};
这意味着，据CLR所知，1月、3月、5月、7月、8月、10月和12月是完全相同的。四月、六月、九月和十一月也是如此。
正确的方法是这样的：
public enum Months
{
None = -1,
January = 1,
February = 2,
March = 3,
April = 4,
May = 5,
June = 6,
July = 7,
August = 8,
September = 9,
October = 10,
November = 11,
December = 12
};
然后你的DetermineMonth方法就是这样：
public static Months DetermineMonth(int userInput)
{
Months temp = (Months)userInput;
return Enum.IsDefined(typeof(Months), temp) ? temp : Months.None;
}
然后DetermineDaysInMonth将是这样的：
public static int DetermineDaysInMonth(int userInput)
{
if (!((Months[])Enum.GetValues(typeof(Months))).Contains((Months)userInput)
return 0;
else return DateTime.DaysInMonth(DateTime.Today.Year, userInput);
}
您可以在enum上使用Extension方法来返回天数-
public enum Months
{
January,
February,
March,
April,
May,
June,
July,
August,
September,
October,
November,
December
}
public static class MonthsExtensions
{
public static int DaysInMonths(this Months month)
{
switch (month)
{
case Months.January:
case Months.March:
case Months.May:
case Months.July:
case Months.August:
case Months.October:
case Months.December:
return 31;
case Months.April:
case Months.June:
case Months.September:
case Months.November:
return 30;
case Months.February:
return 28;
}
return 0;
}
然后你可以得到这样的天数-
int daysInMonths = Months.January.DaysInMonths();