尝试/捕捉和循环

Question

1) 尝试捕获后，我想再次循环它以提供新数字("Console.ReadLine("Give correct number"))，因为用户没有输入可转换为双精度的字符串 2第二个问题是，当用户输入错误号码时，我想再次循环输入新号码。这个版本的程序给小号或大号发消息并退出

修正

double number=10,11;
Console.WriteLine("Give a number");
string w=Console.ReadLine();
try
{
double d = Convert.ToDouble(w);
}
catch(FormatException)
{
Console.WriteLine("it is not a number");        
}
double dd=Convert.ToDouble(w);
if (dd == number)
{
Console.WriteLine("Yes, it is!");
}
else if (number<dd)
{
Console.WriteLine("to big number");
}
else if(number>dd)
{
Console.WriteLine("to small number");
}
Console.ReadLine();

Answer 1

首先，使用do..while(condition) 不断询问，直到用户输入有效号码。其次，使用TryParse 来检查值是否有效。这比异常处理和转换两次要好。不确定您为什么使用doubles，但ints 可能更合适。

bool valid = false;
do
{
    bool newValidState;
    Console.WriteLine("Give a number");

    string w = Console.ReadLine();

    double d;
    if (!double.TryParse(w, out d))
    {
        Console.WriteLine("it is not a number");
        newValidState = false;
    }
    else if (d == number)
    {
        Console.WriteLine("Yes, it is!");
        newValidState = true;
    }
    else if (wyliczona < wybor) // these conditions seem unrelated to `d`
                                // are they okay?
    {
        Console.WriteLine("to big number");
        newValidState = false;
    }
    else if(wyliczona > wybor)
    {
        Console.WriteLine("to small number");
        newValidState = false;
    }
    else
    {
        Console.WriteLine("unknown condition. needs work.");
        newValidState = false;
    }

    valid = newValidState;
}
while (!valid);

注意newValidState 的使用，这将确保您始终为valid 分配一个新值。这有助于防止由于从不设置值而导致的无限循环。除非每个分支都将newValidState 设置为一个值，否则代码不会编译。

Answer 2

试试这个：

var number =3;
do{
    Console.WriteLine("Give a number");
    string w=Console.ReadLine();
    try
    {
        double d = Convert.ToDouble(w);
    }
    catch(FormatException)
    {
        Console.WriteLine("it is not a number");
        continue; // not a number starting new iteration of the loop
    }
    double dd=Convert.ToDouble(w);
    if (dd == number)
    {
        Console.WriteLine("Yes, it is!");
        break; // The number guessed exiting loop
    }
    else if (dd>number)
    {
        Console.WriteLine("to big number");
    }
    else if(dd<number)
    {
        Console.WriteLine("to small number");
    }
}
while (true);
Console.ReadLine();