为什么我的 foreach 循环打印的输出不正确？

Question

我做了一个foreach循环，它将接受用户的输入并减去同一行上的两个数字，我希望它能打印出任何两个数字之间的差，但它没有。相反，当我运行代码并输入数字时，它打印了一个不同的答案，这对我来说没有意义。我对c#有点陌生，所以我只是在尝试一些东西，但如果有人知道我的代码有什么问题，请帮我找出它有什么问题。谢谢！

using System;

public class Program 
{
string sequence;
double answer;

public void Main()
{
Console.WriteLine("<<SUBTRACTION CODE>>");
Console.WriteLine("");
Console.WriteLine("Enter a sequence of numbers and an operator to get subtracted answer ");
Console.WriteLine("Eg: 10-5");
sequence = Console.ReadLine();

foreach (var operation in sequence.Split('-'))
{
answer -= double.Parse(operation); 
}
Console.WriteLine(answer);
Console.ReadLine();
} 
}

Answer 1

您的answer最初将是0。因此，当你做answer -=时，你从零减去右手部位(例如5(，这将导致负面结果。我想你需要为你的answer:分配第一个操作员

using System;

public class Program 
{
string sequence;
double answer;

public void Main()
{
Console.WriteLine("<<SUBTRACTION CODE>>");
Console.WriteLine("");
Console.WriteLine("Enter a sequence of numbers and an operator to get subtracted answer ");
Console.WriteLine("Eg: 10-5");
sequence = Console.ReadLine();
var parts = sequence.Split('-');
answer = parts[0];
for(int i = 1; i < parts.Length; i++)
{
answer -= double.Parse(parts[i]); 
}
Console.WriteLine(answer);
Console.ReadLine();
} 
}

当然，您应该检查parts中是否至少有两个元素。

Answer 2

假设您想要5而不是-15？

你需要用第一个数字初始化答案的值，而不是从零开始减去所有的值。

bool init;
string sequence;
double answer;
public void Main()
{
Console.WriteLine("<<SUBTRACTION CODE>>");
Console.WriteLine("");
Console.WriteLine("Enter a sequence of numbers and an operator to get subtracted answer ");
Console.WriteLine("Eg: 10-5");
sequence = Console.ReadLine();
foreach (var operation in sequence.Split('-'))
{
if (!init) {
answer = double.Parse(operation); 
init = true;
}
else
answer -= double.Parse(operation); 
}
Console.WriteLine(answer);
Console.ReadLine();
}