To round the digits before the decimal point, we can use String.Format() method, here is the example.

为了将小数点前的数字四舍五入，我们可以使用String.Format()方法，这里是示例。

using System;
namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
//Minimum two digits before decimal point
Console.WriteLine("Minimum Two digits before decimal point");
Console.WriteLine(String.Format("{0:00.0}", 12512.4567));
Console.WriteLine(String.Format("{0:00.0}", 512.4567));
Console.WriteLine(String.Format("{0:00.0}", 2.4567)); 
Console.WriteLine(String.Format("{0:00.0}", -2.4567));
//Minimum three digits before decimal point
Console.WriteLine("Minimum Three digits before decimal point");
Console.WriteLine(String.Format("{0:000.0}", 12512.4567));
Console.WriteLine(String.Format("{0:000.0}", 12.4567));
Console.WriteLine(String.Format("{0:000.0}", 2.4567));
Console.WriteLine(String.Format("{0:000.0}", -2.4567));
Console.WriteLine();  
}
}
}

Output

输出量

Minimum Two digits before decimal point
12512.5
512.5
02.5
-02.5
Minimum Three digits before decimal point
12512.5
012.5
002.5
-002.5

翻译自: https://www.includehelp.com/dot-net/rounding-digits-before-decimal-point-using-string-format-method.aspx