尝试比较 C# 中的字符
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Trying to compare chars in C#
提问by JahKnows
I am new to C# I have started learning it to broaden the programming languages to my disposal but I have run into a little problem I did not encounter in neither C nor Java.
我是 C# 的新手我已经开始学习它以扩展我可以使用的编程语言，但是我遇到了一个小问题，我在 C 和 Java 中都没有遇到过。
I am trying to get a user response from the keyboard and then comparing it with probable cases and if none of those cases matched up then I want the user to have to repeat the process until he has entered in a correct value.
我试图从键盘获取用户响应，然后将其与可能的情况进行比较，如果这些情况都不匹配，那么我希望用户必须重复该过程，直到他输入了正确的值。
String input = Console.ReadLine();
while ((input[0] != 'N') || (input[0] != 'Y'))
input = Console.ReadLine();
if (input[0] == 'N')
{
Console.WriteLine("NO");
Console.ReadKey();
}
else if (input[0] == 'Y')
{
Console.WriteLine("YES");
Console.ReadKey();
}
This is by far not the most efficient way I have tried, i also tried doing a do while loop and many other variants.
到目前为止，这不是我尝试过的最有效的方法，我还尝试过 do while 循环和许多其他变体。
The problem I encounter is that when the while loop is not activated everything works just fine, but when I add it in, it always enters the loop even if the input is N or Y and can never leave the loop even though it is clear that it is wrong.
我遇到的问题是，当 while 循环未激活时，一切正常，但是当我添加它时，即使输入是 N 或 Y，它也总是进入循环，并且永远不会离开循环，即使很明显这是错误的。
Please if someone can give me some insight as to why this is occurring or if someone may propose a better way of doing this it would be greatly appreciated. Thank you.
请如果有人能给我一些关于为什么会发生这种情况的见解，或者如果有人可以提出更好的方法，我将不胜感激。谢谢你。
Karim
卡里姆
采纳答案by Brandon
Right now, the conditional in your while statement will always be true. A good way to test for this is to put a breakpoint where the while loop is being tested, and then "Add watch" to each part of the conditional.
现在，while 语句中的条件将始终为真。对此进行测试的一个好方法是在测试 while 循环的位置放置一个断点，然后“添加监视”到条件的每个部分。
Change
改变
while ((input[0] != 'N') || (input[0] != 'Y'))
to
到
while ((input[0] != 'N') && (input[0] != 'Y'))
回答by Dan Hunex
Well your condition is the problem. Your two conditions are Ored , meaning if one of the condition is true, then the loop will execute. So you first Or the conditions and Not the result like !(condition1 || condition2) as in below
那么你的条件是问题。您的两个条件是 Ored ，这意味着如果条件之一为真，则循环将执行。所以你首先 Or 条件而不是结果像 !(condition1 || condition2) 如下
String input = Console.ReadLine();
while (!((input[0] != 'N') || (input[0] != 'Y')))
{
input = Console.ReadLine();
}
if (input[0] == 'N')
{
Console.WriteLine("NO");
Console.ReadKey();
}
else if (input[0] == 'Y')
{
Console.WriteLine("YES");
Console.ReadKey();
}
回答by Mudassir Hasan
The problem is in condition checking.
问题在于条件检查。
while ((input[0] != 'N') || (input[0] != 'Y'))
Suppose 'N'is entered.
Now condition (input[0] != 'Y')becomes falseand it should break out of while loop but because of || with (input[0] != 'N')which remains true, the end result in condition comes out to be trueand hence it never breaks out of loop.
假设输入了“N”。现在条件(input[0] != 'Y')变为假，它应该跳出 while 循环，但因为 || 与(input[0] != 'N')这仍然是真实的，最终的结果病情出来是真的，因此它永远不会打破循环了。
Replace ||with &&
替换|| 与&&
回答by Rahul Tripathi
Try this:-
尝试这个：-
String input = Console.ReadLine();
while ((input[0] != 'N') && (input[0] != 'Y'))
{
input = Console.ReadLine();
}
if (input[0] == 'N')
{
Console.WriteLine("NO");
Console.ReadKey();
}
else if (input[0] == 'Y')
{
Console.WriteLine("YES");
Console.ReadKey();
}
回答by Ergwun
As everyone has already pointed out, you are using ||where you should be using &&.
正如每个人都已经指出的那样，您正在使用||应该使用的地方&&。
Beyond that, you are also attempting to access the first character of a string that is possible empty. This will cause an exception if the user just hits 'Enter'.
除此之外，您还试图访问可能为空的字符串的第一个字符。如果用户只是点击“Enter”，这将导致异常。
Since you asked for a better way, here's one alternative, that uses Console.ReadKeyinstead of Console.ReadLine, as you only seem to be interested in getting a character anyway. It also has the advantage that it is not case-sensitive.
由于您要求更好的方法，这里有一个替代方法，它使用Console.ReadKey代替Console.ReadLine，因为无论如何您似乎只对获取角色感兴趣。它还具有不区分大小写的优点。
while (true)
{
ConsoleKeyInfo key = Console.ReadKey();
Console.WriteLine(""); // Just for nice typesetting.
if (key.Key == ConsoleKey.N)
{
Console.WriteLine("NO");
break;
}
if (key.Key == ConsoleKey.Y)
{
Console.WriteLine("YES");
break;
}
}
