如何简单地将两个小数位相加并四舍五入到最接近的两个小数位？

如何解决如何简单地将两个小数位相加并四舍五入到最接近的两个小数位？

第一张照片是我的教授希望我们做的： https://prnt.sc/v1drxs

这是我的代码：

Console.Write("Enter the radius for a circle: ");

double radius = Convert.ToDouble(Console.ReadLine());
double diameter = 2 * radius;
double circumference = Convert.ToDouble(Math.PI * diameter);

Console.WriteLine("\nThe radius of the circle is " + radius + " units.");
Console.WriteLine("The diameter of the circle is " + diameter + " units.");
Console.WriteLine("The circumference of the circle is " + circumference + " units.");

Console.Write("\nPress any key to continue...");

Console.ReadKey();

我尝试过的事情：

我正在使用Microsoft Visual Studio2017。我对编码非常陌生。帮助将不胜感激，谢谢！

解决方法

您可以使用Math.Round(myDouble,2)将值四舍五入到小数点后两位。

但是，如果该值舍入为十进制值为“ X.00”，则将输出“ X”

据我所知，您希望它输出“ X.00”

为此，我们可以使用String.Format方法。

下面是这三种情况的一个例子。

Console.WriteLine("The radius of the circle is " + radius + " units.");
Console.WriteLine("The diameter of the circle is " + diameter + " units.");
Console.WriteLine("The circumference of the circle is " + circumference + " units.");

Console.WriteLine();
Console.WriteLine("The radius of the circle is " + Math.Round(radius,2) + " units");
Console.WriteLine("The diameter of the circle is " + Math.Round(diameter,2) + " units"); 
Console.WriteLine("The circumference of the circle is " + Math.Round(circumference,2) + " units");

Console.WriteLine();
Console.WriteLine(String.Format("The radius of the circle is {0:0.00} units",Math.Round(radius,2)));
Console.WriteLine(String.Format("The diameter of the circle is {0:0.00} units",Math.Round(diameter,2)));
Console.WriteLine(String.Format("The circumference of the circle is {0:0.00} units",Math.Round(circumference,2)));

,

我将在格式说明符中使用内插字符串。通过在字符串前加一个$美元符号，可以向编译器发出信号，告知该字符串在{}大括号内包含需要替换的变量。 F2格式说明符说“显示到小数点后两位”（F代表 floating point ）。您应该查找 standard 和自定义数字格式说明符。

请注意，我使用double.TryParse来解释用户的输入-如果输入错误，我会给他/她另一个机会。如果使用double.Parse或Convert.ToDouble进行此操作，则错误的输入将引发异常。用户以错误的格式输入信息几乎不是 exception 情况，因此，应尽可能避免出现异常。 TryParse调用发出bool而不是异常的错误信号。

double radius;
string responseFromUser;
do
{
    Console.Write("Enter the radius for a circle: ");
    responseFromUser = Console.ReadLine();
} while (!double.TryParse(responseFromUser,out radius));

double diameter = 2 * radius;
double circumference = Convert.ToDouble(Math.PI * diameter);

Console.WriteLine($"{Environment.NewLine}The radius of the circle is {radius:F2} units.");
Console.WriteLine($"The diameter of the circle is {diameter:F2} units.");
Console.WriteLine($"The circumference of the circle is {circumference:F2} units.");

Console.Write($"{Environment.NewLine}Press any key to continue...");

Console.ReadKey();

输出如下：

Enter the radius for a circle: abc
Enter the radius for a circle: 12.333

The radius of the circle is 12.33 units.
The diameter of the circle is 24.67 units.
The circumference of the circle is 77.49 units.

Press any key to continue...

如果输入的小数点少于两个小数，您仍然会得到两个小数点：

Enter the radius for a circle: 4

The radius of the circle is 4.00 units.
The diameter of the circle is 8.00 units.
The circumference of the circle is 25.13 units.

Press any key to continue...