将用户输入限制为仅限数字

Question

C＃[4小时新增:)的新品牌]，但希望在Board Feet Calculator中限制用户输入的指针仅限于数字，不允许使用字母或特殊字符。

首先，限制发生在类，方法和/或程序中吗？ （我相信类和方法）

第二，我已经看到了一个例子，我会用类似的东西吗？

第三，如果是这样，我是否需要为KeyPress和KeyPressEventArgs分别创建类？ （我相信他们会自动出现，例如 public char KeyChar { get; set; }

private void textBox1_KeyPress(object sender, KeyPressEventArgs e) 
{ 
    // allows only letters 
    if (!char.IsLetter(e.KeyChar)) 
    { 
     e.Handled = true; 
    } 
} 

我的计划

namespace BoardFt_MyTry_ 
{ 
    class Program 
    { 
     static void Main(string[] args) 
     { 
      Board board = new Board(); 

     board.lengthOfboard = Convert.ToDouble(askQuestion("What is the length of your board in inches?")); 
     board.widthOfboard = Convert.ToDouble(askQuestion("What is the width of your board in inches?")); 
     board.thicknessOfboard = Convert.ToDouble(askQuestion("What is the thickness of your board in inches?")); 

     Console.WriteLine("Your board has {0} board feet.", board.CalcBoardFt()); 

     Console.ReadLine(); 
    } 
    private static string askQuestion(string question) 
    { 
     Console.WriteLine(question); 
     return Console.ReadLine(); 
    } 

} 

我局级

namespace BoardFt_MyTry_ 
{ 
    class Board 
    { 
     public double lengthOfboard; 
     public double widthOfboard; 
     public double thicknessOfboard; 

    public double CalcBoardFt() 
    { 
     double boardft = 0; 

     boardft = (this.lengthOfboard * this.widthOfboard * this.thicknessOfboard)/144; 

     return boardft; 
    } 
} 
} 

Answer 1

你真的不能做，在一个控制台应用程序。所有你能do是允许用户输入不好的数据，然后告诉用户数据不好。

你可以尝试这样的事情：

class Program 
{ 
    public double AskDnoubleQuestion(string message){ 
     do { 
     Console.Write(message); 
     var input = Console.ReadLine(); 

     if (String.IsNullOrEmpty(input)){ 
      Console.WriteLine("Input is required"); 
      continue; 
     } 
     double result; 
     if (!double.TryParse(input, out result)){ 
      Console.WriteLine("Invalid input - must be a valid double"); 
      continue; 
     } 
     return result; 
    } 

    static void Main(string[] args) 
    { 
     Board board = new Board(); 

    board.lengthOfboard = AskDoubleQuestion("What is the length of your board in inches?"); 
    board.widthOfboard = AskDoubleQuestion(askQuestion("What is the width of your board in inches?"); 
    board.thicknessOfboard = AskDoubleQuestion(askQuestion("What is the thickness of your board in inches?"); 

    Console.WriteLine("Your board has {0} board feet.", board.CalcBoardFt()); 

    Console.ReadLine(); 
} 

Answer 2

如果确认是不是要继续的方式，你可以做这样的事情：

class Program 
{ 
    static void Main(string[] args) 
    { 
     Console.WriteLine("Enter a number:"); 

     string number = ReadNumber(); 
     Console.WriteLine("You entered: " + number); 
    } 

    private static string ReadNumber() 
    { 
     string input = ""; 

     do 
     { 
      ConsoleKeyInfo keyInfo = Console.ReadKey(true); 
      if (char.IsNumber(keyInfo.KeyChar)) 
      { 
       input = input + keyInfo.KeyChar; 
       Console.Write(keyInfo.KeyChar); 
      } 
      if (keyInfo.Key == ConsoleKey.Enter) 
      { 
       Console.WriteLine(); 
       break; 
      } 
      if (keyInfo.Key == ConsoleKey.Backspace) 
      { 
       input = input.Substring(0, input.Length - 1); 
       Console.Write("\b \b"); 
      } 
     } while (true); 

     return input; 
    } 
} 

这将使用户仅输入数字。如果你愿意，你可以按照你的意愿过滤它。例如，只有字母和数字等......

就目前来看，它只允许整数。如果你想允许一个小数点，改变线以上，以这样的：if (char.IsNumber(keyInfo.KeyChar) || keyInfo.KeyChar == '.')

Answer 3

你可以写，其读取由关键（在控制台中不显示）密钥的方法，忽略了非数字字符，打印有效字符并追加到一个StringBuilder实例，像这样：

public static string ReadOnlyNumbers() 
{ 
    StringBuilder input = new StringBuilder(); 
    ConsoleKeyInfo ckey; 

    while ((ckey = Console.ReadKey(true)).Key != ConsoleKey.Enter) 
    { 
     if (Char.IsDigit(ckey.KeyChar)) 
     { 
      Console.Write(ckey.KeyChar); 
      input.Append(ckey.KeyChar); 
     } 

     if (ckey.Key == ConsoleKey.Backspace) 
     { 
      input.Length--; 
      Console.Write("\b \b"); 
     } 
    } 

    Console.Write(Environment.NewLine); 
    return input.ToString(); 
} 

然后，您可以使用这样的：

string input = ReadOnlyNumbers(); 
Console.WriteLine(input);