以下是中文四舍五入的算法，不是银行的四舍五入。
public static class NumbericExtension
{
/// <summary>
/// 四舍五入法
/// </summary>
/// <param name="sourceNum">要进行处理的数据</param>
/// <param name="toRemainIndex">保留的小数位数</param>
/// <returns>四舍五入后的结果</returns>
public static decimal ChineseRound(this decimal sourceNum, int toRemainIndex)
{
decimal result = sourceNum;
string sourceString = sourceNum.ToString();
//没有小数点,则返回原数据+"."+"保留小数位数个0"
if (!sourceString.Contains("."))
{
result = Convert.ToDecimal(sourceString + "." + CreateZeros(toRemainIndex));
return result;
}
//小数点的位数没有超过要保留的位数,则返回原数据+"保留小数位数 - 已有的小数位"个0
if ((sourceString.Length - sourceString.IndexOf(".") - 1) <= toRemainIndex)
{
result = Convert.ToDecimal(sourceString + CreateZeros(toRemainIndex - (sourceString.Length - sourceString.IndexOf(".") - 1)));
return result;
}
string beforeAbandon_String = string.Empty;
beforeAbandon_String = sourceString.Substring(0, sourceString.IndexOf(".") + toRemainIndex + 1);
//取得如3.1415926保小数点后4位(原始的,还没开始取舍)，中的3.1415
decimal beforeAbandon_Decial = Convert.ToDecimal(beforeAbandon_String);
//如果保留小数点后N位，则判断N+1位是否大于等于5，大于，则进一，否则舍弃。
if (int.Parse(sourceString.Substring(sourceString.IndexOf(".") + toRemainIndex + 1, 1)) >= 5)
{
string toAddAfterPoint = "0." + CreateZeros(toRemainIndex - 1) + "1";
result = beforeAbandon_Decial + Convert.ToDecimal(toAddAfterPoint);
}
else
{
result = beforeAbandon_Decial;
}
return result;
}
/// <summary>
/// 补 "0"方法.
/// </summary>
/// <param name="zeroCounts">生成个数.</param>
/// <returns></returns>
private static string CreateZeros(int zeroCounts)
{
string Result = string.Empty;
if (zeroCounts == 0)
{
Result = "";
return Result;
}
for (int i = 0; i < zeroCounts; i++)
{
Result += "0";
}
return Result;
}
}