用戶輸入無效後程序結束

Question

如何讓程序狀態爲用戶輸入無效，然後在輸入完成後關閉？我有第一個錯誤，指出用戶輸入的值是錯誤的，給他們另一次嘗試，但如果用戶鍵入相同/無效的數字，它會重複最後一件事。我怎麼能限制到一個更多的嘗試，然後如果用戶沒有提供有效的條目，它會正確和錯誤？代碼如下：

 string First; 
     string Last; 
     First = "Cristiano"; 
     Last = " Ronaldo"; 
     Console.Write("Please enter student name <First Last>: "); 
     Console.WriteLine(First + Last); 

     Console.WriteLine(" "); 

     Console.WriteLine("*************NOTE**********************************************"); 
     Console.WriteLine("*** Be sure to include decimal point for scores.   ***"); 
     Console.WriteLine("***  !!!All score should range from 0.00 to 100.00 !! ***"); 
     Console.WriteLine("***               ***"); 
     Console.WriteLine("*** For example : 80.50          ***"); 
     Console.WriteLine("***************************************************************"); 

     Console.WriteLine(" "); 

     double Exam_1 = -1; 
     double Exam_2; 
     double Exam_3; 
     double Assignment_1; 
     double Assignment_2; 

     Console.Write("Please enter score for Exam 1 <Example: 100.0>: "); 
     Exam_1 = Convert.ToDouble(Console.ReadLine()); 

     while (Exam_1 < 0.0 || Exam_1 > 100.0) 
     { 
      Console.Write("Exam score cannot be less than 0. or greater than 100.0. Please re-enter the score for Exam 1 <Example: 95.0>:"); 
      Exam_1 = Convert.ToDouble(Console.ReadLine()); 
     } 

     Console.Write("Please enter score for Exam 2 <Example: 0.0>: "); 
     Exam_2 = Convert.ToDouble(Console.ReadLine()); 

     while (Exam_2 < 0.0 || Exam_2 > 100.0) 
     { 
      Console.Write("Exam score cannot be less than 0.0 or greater than 100.0. Please re-enter the score for Exam 2 <Example: 95.0>:"); 
      Exam_2 = Convert.ToDouble(Console.ReadLine()); 
     } 

     Console.Write("Please enter score for Exam 3 <Example: 60.8>: "); 
     Exam_3 = Convert.ToDouble(Console.ReadLine()); 

     while (Exam_3 < 0.0 || Exam_3 > 100.0) 
     { 
      Console.Write("Exam score cannot be less than 0.0 or greater than 100.0. Please re-enter the score for Exam 3 <Example: 95.0>:"); 
      Exam_3 = Convert.ToDouble(Console.ReadLine()); 
     } 

     Console.WriteLine(" "); 

     Console.Write("Please enter score for Assignment 1 <Example: 100.0>: "); 
     Assignment_1 = Convert.ToDouble(Console.ReadLine()); 

     while (Assignment_1 < 0.0 || Exam_2 > 100.0) 
     { 
      Console.Write("Assignment score cannot be less than 0.0 or greater than 100.0. Please re-enter the score for Assignment 1 <Example: 95.0>:"); 
      Assignment_1 = Convert.ToDouble(Console.ReadLine()); 
     } 

     Console.Write("Please enter score for Assignment 2 <Example: 23.46>: "); 
     Assignment_2 = Convert.ToDouble(Console.ReadLine()); 

     while (Assignment_2 < 0.0 || Assignment_2 > 100.0) 
     { 
      Console.Write("Assignment score can not be less than 0.0 or greater than 100.0. Please re-enter the score for Assignment 2 <Example: 56.0>: "); 
      Assignment_2 = Convert.ToDouble(Console.ReadLine()); 
     } 

     Console.WriteLine(" "); 

     Console.WriteLine(" -------------- OUTPUT ---------------"); 

     Console.WriteLine(" "); 

     Console.Write("Student: "); 
     Console.WriteLine(First + Last); 

     Console.WriteLine(" "); 



















     Console.Write("Press any key to continue . . . "); 
     Console.ReadLine(); 
    } 
} 

}

Answer 1

試試這個代碼

static void Main(string[] args) 
    { 
     string First; 
     string Last; 
     First = "Cristiano"; 
     Last = " Ronaldo"; 
     Console.Write("Please enter student name <First Last>: "); 
     Console.WriteLine(First + Last); 

     Console.WriteLine(" "); 

     Console.WriteLine("*************NOTE**********************************************"); 
     Console.WriteLine("*** Be sure to include decimal point for scores.   ***"); 
     Console.WriteLine("***  !!!All score should range from 0.00 to 100.00 !! ***"); 
     Console.WriteLine("***               ***"); 
     Console.WriteLine("*** For example : 80.50          ***"); 
     Console.WriteLine("***************************************************************"); 

     Console.WriteLine(" "); 

     double Exam_1 = -1; 
     double Exam_2; 
     double Exam_3; 
     double Assignment_1; 
     double Assignment_2; 

     Console.Write("Please enter score for Exam 1 <Example: 100.0>: "); 
     Exam_1 = Convert.ToDouble(Console.ReadLine()); 
     var exitProgram = false; 
     var errorCount = 0; 

     while (Exam_1 < 0.0 || Exam_1 > 100.0) 
     { 
      Console.Write("Exam score cannot be less than 0. or greater than 100.0. Please re-enter the score for Exam 1 <Example: 95.0>:"); 
      Exam_1 = Convert.ToDouble(Console.ReadLine()); 
      ++errorCount; 
      ErrorCount(errorCount); 
     } 

     Console.Write("Please enter score for Exam 2 <Example: 0.0>: "); 
     Exam_2 = Convert.ToDouble(Console.ReadLine()); 
     errorCount = 0; 
     while (Exam_2 < 0.0 || Exam_2 > 100.0) 
     { 
      Console.Write("Exam score cannot be less than 0.0 or greater than 100.0. Please re-enter the score for Exam 2 <Example: 95.0>:"); 
      Exam_2 = Convert.ToDouble(Console.ReadLine()); 
      ++errorCount; 
      ErrorCount(errorCount); 
     } 

     Console.Write("Please enter score for Exam 3 <Example: 60.8>: "); 
     Exam_3 = Convert.ToDouble(Console.ReadLine()); 
     errorCount = 0; 
     while (Exam_3 < 0.0 || Exam_3 > 100.0) 
     { 
      Console.Write("Exam score cannot be less than 0.0 or greater than 100.0. Please re-enter the score for Exam 3 <Example: 95.0>:"); 
      Exam_3 = Convert.ToDouble(Console.ReadLine()); 
      ++errorCount; 
      ErrorCount(errorCount); 
     } 

     Console.WriteLine(" "); 

     Console.Write("Please enter score for Assignment 1 <Example: 100.0>: "); 
     Assignment_1 = Convert.ToDouble(Console.ReadLine()); 
     errorCount = 0; 
     while (Assignment_1 < 0.0 || Exam_2 > 100.0) 
     { 
      Console.Write("Assignment score cannot be less than 0.0 or greater than 100.0. Please re-enter the score for Assignment 1 <Example: 95.0>:"); 
      Assignment_1 = Convert.ToDouble(Console.ReadLine()); 
      ++errorCount; 
      ErrorCount(errorCount); 
     } 

     Console.Write("Please enter score for Assignment 2 <Example: 23.46>: "); 
     Assignment_2 = Convert.ToDouble(Console.ReadLine()); 
     errorCount = 0; 
     while (Assignment_2 < 0.0 || Assignment_2 > 100.0) 
     { 
      Console.Write("Assignment score can not be less than 0.0 or greater than 100.0. Please re-enter the score for Assignment 2 <Example: 56.0>: "); 
      Assignment_2 = Convert.ToDouble(Console.ReadLine()); 
      ++errorCount; 
      ErrorCount(errorCount); 
     } 

     Console.WriteLine(" "); 

     Console.WriteLine(" -------------- OUTPUT ---------------"); 

     Console.WriteLine(" "); 

     Console.Write("Student: "); 
     Console.WriteLine(First + Last); 

     Console.WriteLine(" "); 
     Console.Write("Press any key to continue . . . "); 
     Console.ReadLine(); 
    } 

    public static void ErrorCount(int errorCount) 
    { 
     if (errorCount > 0) 
     { 
      Console.Write("Error count too much ! . . . "); 
      Console.Write("Press any key to exit . . . "); 
      Console.ReadKey(); 
      Environment.Exit(0); 
     } 

    } 

請記住，如果用戶輸入一個字母數字號碼或特殊字符，但你的想法不檢測。

Answer 2

鑑於這是一個任務，我不知道，如果你的教授是像我這樣的事情，我們只能用我們在課堂上所學到。也就是說，您可能想要查看double.tryparse https://msdn.microsoft.com/en-us/library/994c0zb1(v=vs.110).aspx

如果輸入可以解析爲double，則函數將返回bool，如果輸入無效，則返回false。上面的MSDN代碼示例應該給你一個很好的開始。

Answer 3

你顯然是編程界的新手，這看起來像一個家庭作業問題。但是，我懷疑你突出顯示的問題根源在於，如果調用Convert.ToDouble(Console.ReadLine())（其中輸入無法轉換），則會拋出異常並且不會捕獲它。

你可以閱讀更多有關異常的位置：https://msdn.microsoft.com/en-us/library/ms173160.aspx

要解決，我會實現這樣的事情：

Console.Write("Please enter score for Exam 1 <Example: 100.0>: "); 
while(!Double.TryParse(Console.ReadLine(), out Exam_1)) 
{ 
     Console.Write("Try again..."); 
} 

Answer 4

看看你的代碼的邏輯。 while循環會持續循環，直到表達式計算結果爲false。如果您希望儘早終止循環，則需要通過更改條件表達式，使用不同類型的循環或使用break語句來修改循環。

Here is some reference material from Microsoft's website.

想通過你的問題，並問自己：你會怎樣做，如果你是手動這樣做呢？如果你在電腦的地方，你會採取什麼邏輯步驟？你會做出什麼樣的決定，你需要哪些信息來做出這些決定？