C#四舍五入(函数)用法实例

效果：

说明：输入小数，然后输入要保留的位数，

事件：点击button

代码：

public static double round(double d, int i)
        {
            if (d >= 0)
            {
                d += 5 * math.pow(10, -(i + 1));//求指定次数的指定次幂
            }
            else
            {
                d += 5 * math.pow(10, -(i + 1));
            }
            string str = d.tostring();
            string[] strs = str.split('.');
            int idot = str.indexof('.');
            string prestr = strs[0];
            string poststr = strs[1];
            if (poststr.length > i)
            {
                poststr = str.substring(idot + 1, i);//截取需要位数
            }
            if (poststr.length <= 2)
            {
                poststr = poststr + "0";
            }
            string strd = prestr + "." + poststr;
            d = double.parse(strd);//将字符串转换为双精度实数
            return d;
        }

        private void button1_click(object sender, eventargs e)
        {
            textbox3.text=convert.tostring(math.round(convert.todouble(textbox1.text.trim()),convert.toint16(textbox2.text.trim())));
        }