c# 小數四舍五入，向上取整，向下取整，見角進元保留多個小數位數

/// <summary>
        /// 實現數據的四舍五入法
        /// </summary>
        /// <param name="v">要進行處理的數據</param>
        /// <param name="x">保留的小數位數</param>
        /// <returns>四舍五入后的結果</returns>
        public decimal Round(decimal v, int x)
        {
            var isNegative = false;
            //如果是負數
            if (v < 0)
            {
                isNegative = true;
                v = -v;
            }

            var IValue = 1;
            for (var i = 1; i <= x; i++)
            {
                IValue = IValue * 10;
            }

            var Int = Math.Round(v * IValue, 0);
            v = Int / IValue;

            if (isNegative)
            {
                v = -v;
            }

            return v;
        }

        /// <summary>
        /// 實現數據的向上取整
        /// </summary>
        /// <param name="v">要進行處理的數據</param>
        /// <param name="x">保留的小數位數</param>
        /// <returns>向上取整后的結果</returns>
        public decimal Ceiling(decimal v, int x)
        {
            var isNegative = false;
            //如果是負數
            if (v < 0)
            {
                isNegative = true;
                v = -v;
            }

            var IValue = 1;
            for (var i = 1; i <= x; i++)
            {
                IValue = IValue * 10;
            }

            var Int = Math.Ceiling(v * IValue);
            v = Int / IValue;

            if (isNegative)
            {
                v = -v;
            }

            return v;
        }

        /// <summary>
        /// 實現數據的向下取整
        /// </summary>
        /// <param name="v">要進行處理的數據</param>
        /// <param name="x">保留的小數位數</param>
        /// <returns>向下取整后的結果</returns>
        public decimal Floor(decimal v, int x)
        {
            var isNegative = false;
            //如果是負數
            if (v < 0)
            {
                isNegative = true;
                v = -v;
            }

            var IValue = 1;
            for (var i = 1; i <= x; i++)
            {
                IValue = IValue * 10;
            }

            var Int = Math.Floor(v * IValue);
            v = Int / IValue;

            if (isNegative)
            {
                v = -v;
            }

            return v;
        }

        /// <summary>
        /// 實現見角進元
        /// </summary>
        /// <param name="v">要進行處理的數據</param>
        /// <param name="x">保留的小數位數</param>
        /// <returns>見角進元后的結果</returns>
        public decimal SeeDownUp(decimal v, int x)
        {
            var isNegative = false;
            //如果是負數
            if (v < 0)
            {
                isNegative = true;
                v = -v;
            }

            var IValue = 1;
            for (var i = 1; i <= x; i++)
            {
                IValue = IValue * 10;
            }

            var stirngpanduan = Math.Floor(v * IValue * 10).ToString();
            if (stirngpanduan.Substring(stirngpanduan.Length - 1) == "0")
            {
                var Int = Math.Floor(v * IValue);
                v = Int / IValue;
            }
            else
            {
                var Int = Math.Ceiling(v * IValue);
                v = Int / IValue;
            }

            if (isNegative)
            {
                v = -v;
            }

            return v;
        }

        /// <summary>
        /// 實現數據的四舍五入，向上取整，向下取整
        /// </summary>
        /// <param name="v">要進行處理的數據</param>
        /// <param name="x">保留的小數位數</param>
        /// <param name="type">1四舍五入，2向上取整，3向下取整</param>
        /// <returns>decimal</returns>
        public decimal DecimalProcessing(decimal v, int x, string type)
        {
            decimal result = 0;
            switch (type)
            {
                case "1":
                    result = Round(v, x);
                    break;
                case "2":
                    result = Ceiling(v, x);
                    break;
                case "3":
                    result = Floor(v, x);
                    break;
                case "4":
                    result = SeeDownUp(v, x);
                    break;
                default:
                    result = Round(v, x);
                    break;
            }

            return result;
        }