Question

1）尝试并捕获后我想再次循环它以给出新的数字（“Console.ReadLine（”给出正确的数字“））因为用户没有输入字符串convertable到double 2第二个问题是，当用户提供错误号码时，我想再次循环输入新号码。此版本的程序会向小号或大号号码发送消息并退出

校正

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SELECT DeptID, EmpName, Salary FROM EmpDetails a WHERE Salary = (SELECT MAX(Salary) FROM EmpDetails b WHERE a.DeptID = b.DeptID)继续询问，直到用户输入有效数字。其次，使用do..while(condition)检查值是否有效。这比异常处理和转换两次要好。不确定您使用TryParse的原因，但double可能更合适。

int

请注意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);的使用，这将确保您始终为newValidState分配新值。这有助于防止由于从未设置值而导致的无限循环。除非每个分支都将valid设置为值，否则代码将无法编译。

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();

尝试/捕捉和循环

2 个答案: