不是家庭作业。所以我有一个简单的控制台程序来读取考试成绩并打印出平均值和成绩。到目前为止,它如下:
public static void Main ()
{
int sum = 0;
int count = 0;
double average = 0;
Console.WriteLine ("Enter all your exam scores one by one. When finished, enter -99");
string scores = Console.ReadLine ();
while (scores != "-99") {
sum += int.Parse (scores);
count++;
scores = Console.ReadLine ();
}
if (scores == "-99") {
average = sum / count;
if (average >= 90)
Console.WriteLine ("Your average score is {0}. This is good for a letter grade of A", average);
Console.WriteLine(....more scores etc...);
现在我想用 TryParse 检查无效条目。我想我会在另一个循环之前坚持另一个 while 循环并像这样更改原始循环:
Console.WriteLine ("Enter all your exam scores one by one. When finished, enter -99");
string scores = Console.ReadLine ();
while (int.TryParse(scores, out numbers) == false){
Console.WriteLine("Please enter a valid integer")
scores = Console.ReadLine();
sum += int.Parse(scores);
count++;
}
while (scores != "-99" && int.TryParse(scores, out numbers) == true) {
sum += int.Parse (scores);
count++;
scores = Console.ReadLine ();
}
if (scores == "-99") {
average = sum / count;
if (average >= 90)
Console.WriteLine ("Your average score is {0}. This is good for a letter grade of A", average); ...etc...
这里的问题是,如果用户首先输入有效条目,然后输入无效条目,编译器将无法返回到第一个 while 循环来检查无效条目。所以我尝试交换 while 循环的位置。但这具有相同的效果;输入无效条目后,它无法返回到第一个 while 循环以检查有效条目。答案很可能很简单,但我被困住了。
您遇到的问题是,当TryParse
返回true
时,您从第一个循环中断,但没有办法重新进入循环。 相反,你应该嵌套你的循环。 带有哨兵的循环应该是外部循环,验证和重新提示用户的循环应该是内部循环。 下面是一个示例:
while(scores != "-99")
{
scores = Console.ReadLine();
while((int.TryParse(scores, out numbers) == false)
{
//validation failed, re-prompt user for better number
Console.WriteLine("Bad value, try again")
scores = Console.ReadLine()
}
//do stuff here with the valid score value
}