C＃方法返回公式

Question

static void Main(string[] args) 
     { 
      double creditcardbalance; 
      creditcardbalance = GetPositiveDouble("Enter In Credit Card Balance"); 

      double monthlypayementamount; 
      monthlypayementamount = GetPositiveDouble("Enter In Monthly Payement Amount"); 

      double percentagerate; 
      percentagerate = (int)GetPositiveDecimal("Enter In Percentage Rate"); 

      CreditCardMonths(); 
     } 

     static void CreditCardMonths() 
     { 
      double dailyinterestrate; 
      double payoff; 
      double percentagerate = 0; 
      double creditcardbalance = 0; 
      double monthlypayementamount = 0; 

      dailyinterestrate = (double)percentagerate/365; 
      payoff = (int)(-(1d/30) * Math.Log(1 + creditcardbalance/monthlypayementamount * (1 - Math.Pow(1 + dailyinterestrate, 30)))/Math.Log(1 + dailyinterestrate)) + 1; 

      Console.WriteLine("It will take {0} months to pay off the loan", payoff); 
      displaymenu(); 
      Console.ReadKey(); 
     }  

一旦在主方法中聲明瞭方法CreditCardMonths（），我的公式的答案返回一個負整數，當它應該返回一個正數。 我在想什麼？

我完整的代碼：

using System; 
using System.Collections.Generic; 
using System.Linq; 
using System.Text; 
using System.Threading.Tasks; 

namespace DebtCalculator 
{ 
    class Program 
    { 
     static void Main(string[] args) 
     { 
      double creditcardbalance; 
      creditcardbalance = GetPositiveDouble("Enter In Credit Card Balance"); 
      double monthlypayementamount; 
      monthlypayementamount = GetPositiveDouble("Enter In Monthly Payement Amount"); 

      double percentagerate; 
      percentagerate = (int)GetPositiveDecimal("Enter In Percentage Rate"); 

      CreditCardMonths(); 
     } 

這是一段代碼的工作原理：

double creditcardbalance; 
      Console.WriteLine("Enter in credit card balance:"); 
      creditcardbalance = double.Parse(Console.ReadLine()); 

      double monthlypayementamount; 
      Console.WriteLine("Enter in the monthly payement amount:"); 
      monthlypayementamount = double.Parse(Console.ReadLine()); 

      double percentagerate; 
      Console.WriteLine("Enter in annual percentage rate:"); 
      percentagerate = double.Parse(Console.ReadLine()); 
      // outputs 
      double payoff; 
      double dailyinterestrate; 

      // Daily interest formula calculated by apr divided by 365 
      dailyinterestrate = percentagerate/365; 
      //Introducing formula for output 
      //Payoff needed to display whole numbers, although in ints output 1/30 = 0 so adding 1d (double) allows precise calculation.+1 allows it to round up to the nearest dollar. 
      payoff = (int)(-(1d/30) * Math.Log(1 + creditcardbalance/monthlypayementamount * (1 - Math.Pow(1 + dailyinterestrate, 30)))/Math.Log(1 + dailyinterestrate)) + 1; 
      //Introduce output for display 

      { 
       Console.WriteLine("It will take {0} months to pay off the loan", payoff); 
       Console.WriteLine("Goodbye"); 
       // keep console open 
       Console.ReadKey(); 

但似乎通過創建一個名爲CreditCardMonths的方法返回一個負整數？ 另外我的Y/N for循環方法不起作用。

 static void CreditCardMonths() 
     { 
      double dailyinterestrate; 
      double payoff; 
      double percentagerate = 0; 
      double creditcardbalance = 0; 
      double monthlypayementamount = 0; 

      dailyinterestrate = (double)percentagerate/365; 
      payoff = (int)(-(1d/30) * Math.Log(1 + creditcardbalance/monthlypayementamount * (1 - Math.Pow(1 + dailyinterestrate, 30)))/Math.Log(1 + dailyinterestrate)) + 1; 

      Console.WriteLine("It will take {0} months to pay off the loan", payoff); 
      displaymenu(); 
      Console.ReadKey(); 
     }  

     static decimal GetPositiveDecimal(string message) 
     { 
      decimal value = 0; 
      Console.WriteLine(message); 
      value = decimal.Parse(Console.ReadLine()); 
      while (value <= 0) 
      { 
       Console.WriteLine("invalid input. Please enter a non negative Decimal"); 
       Console.WriteLine(message); 
       value = decimal.Parse(Console.ReadLine()); 
      } 
      return value; 
     } 
     static double GetPositiveDouble(string message) 
     { 
      double value = 0; 
      Console.WriteLine(message); 
      value = double.Parse(Console.ReadLine()); 
      while (value <= 0) 
      { 
       Console.WriteLine("Invalid Input . Enter In A Non Negative Number"); 
       Console.WriteLine(message); 
       value = double.Parse(Console.ReadLine()); 
      } 
      return value; 
     } 
     static void menuItem() 
     { 
      char menuItem; 
      { 
       menuItem = GetUpperCaseYN(); 
       ProcessMenuItem(menuItem); 
      } 
      Console.WriteLine("Thank you, goodbye."); 
      Console.ReadLine(); 
     } 
     static char GetUpperCaseYN() 
     { 
      char menuItem; 
      menuItem = char.Parse(Console.ReadLine()); 
      menuItem = char.ToUpper(menuItem); 
      while (menuItem != 'Y' && menuItem != 'N') 
      { 
       Console.WriteLine("Invalid Menu Item"); 
       menuItem = char.Parse(Console.ReadLine()); 
       menuItem = char.ToUpper(menuItem); 
      } 

      return menuItem; 
     } 
     static void displaymenu() 
     { 
      Console.WriteLine("Calculate Another? (Y/N)"); 
     } 

     static void ProcessMenuItem(char menuItem) 
     { 
      switch (menuItem) 
      { 

       case 'Y': 
        ; 
        break; 

       case 'N': 
        Console.ReadKey(); 
        Console.WriteLine("Goodbye!"); 
        Console.ReadKey(); 
        break; 
      } 
      Console.ReadKey(); 
     } 
    } 
} 

Answer 1

你缺少一個事實，即在一個方法變量是不同的變量，然後在其他方法變量，即使它們具有相同的名稱。

因此，例如，您可以在方法Main中使用可變百分比，在CreditCardMonths方法中使用可變倍數百分比。它們是不同的記憶片段 - 不同的變量。 您需要執行以下操作之一： 在類級別聲明方法之外的變量。 您的方法是statis，所以你需要包括關鍵字static。

static double creditcardbalance; 
static double monthlypayementamount; 
static double percentagerate; 

static void Main(string[] args) 
    { 
     creditcardbalance = GetPositiveDouble("Enter In Credit Card Balance"); 

     monthlypayementamount = GetPositiveDouble("Enter In Monthly Payement Amount"); 

     percentagerate = (int)GetPositiveDecimal("Enter In Percentage Rate"); 

     CreditCardMonths(); 
    } 

並且不要在第二種方法中聲明它們，因爲它會（所謂的）隱藏範圍。

注意：當您瞭解有關編程的更多信息時，請考慮使用方法參數將子方法需要的數據傳遞給它們。

https://msdn.microsoft.com/en-us/library/0f66670z.aspx