我也尝试写了下，核心代码如下。

#region  常量定义

/// <summary>
/// 亿，万万
/// </summary>
private const int HUNDRED_MILLION = 100000000;

/// <summary>
/// 万，十千
/// </summary>
private const int TEN_THOUSAND = 10000;

private const int THOUSAND = 1000;

private const int HUNDRED = 100;

private const int TEN = 10;

/// <summary>
/// 万亿(不包含)
/// </summary>
private const double MAX_MONEY = 1000000000000;

/// <summary>
/// 金额不能为负，最小值为0.
/// </summary>
private const double MIN_MONEY = 0;

private const string AMOUT_STRING = "零壹贰叁肆伍陆柒捌玖";

#endregion

#region 工具库

private string GetMoneyAmout(double money)
{
    var rightMoney = GetMoneyFormat(money);
    //整数部分
    var longPart = (long) rightMoney;
    //小数部分
    var decimalPart = rightMoney - longPart;

    var longPartAmout = this.ConvertLongPartToAmout(longPart);
    var decimalPartAmout = this.ConvertDecimalPartToAmout(decimalPart);

    return longPartAmout + (string.IsNullOrEmpty(decimalPartAmout) ? "整" : decimalPartAmout);
}

private double GetMoneyFormat(double money)
{
    var d = double.Parse(money.ToString("F2"));
    if (d > MAX_MONEY || d < MIN_MONEY)
    {
        throw new ArgumentOutOfRangeException("Money must greater than or equal 0 and less than 1000,000,000,000");
    }
    return d;
}

private string ConvertLongPartToAmout(long longPart)
{
    var amoutBuilder = new StringBuilder();
    while (longPart > 0)
    {
        if (longPart > HUNDRED_MILLION)
        {
            amoutBuilder.AppendFormat("{0}亿", this.NumToChinese((int)longPart / HUNDRED_MILLION));
            longPart %= HUNDRED_MILLION;
        }
        else if (longPart > TEN_THOUSAND)
        {
            amoutBuilder.AppendFormat("{0}万", this.NumToChinese((int)longPart / TEN_THOUSAND));
            longPart %= TEN_THOUSAND;
        }
        else
        {
            amoutBuilder.AppendFormat("{0}", this.NumToChinese((int)longPart));
            longPart = 0;
        }
    }
    amoutBuilder.Append("元");
    return amoutBuilder.ToString();
}
/// <summary>
/// 将10000以内的金额转换为中文大写
/// </summary>
/// <param name="num"></param>
/// <returns></returns>
private string NumToChinese(int num)
{
    var builder = new StringBuilder();
    bool useZero = false;
    while (num > 0)
    {
        if (num >= THOUSAND)
        {
            builder.AppendFormat("{0}仟", AMOUT_STRING[num / THOUSAND]);
            num %= THOUSAND;
            useZero = true;
        }
        else if (num >= HUNDRED)
        {
            builder.AppendFormat("{0}佰", AMOUT_STRING[num / HUNDRED]);
            num %= HUNDRED;
            useZero = false;
        }
        else if (num >= TEN)
        {
            if (useZero)
            {
                builder.Append("零");
            }
            builder.AppendFormat("{0}拾", AMOUT_STRING[num / TEN]);
            num %= TEN;
        }
        else
        {
            builder.Append(AMOUT_STRING[num]);
            num = 0;
        }
    }
    return builder.ToString();
}

private string ConvertDecimalPartToAmout(double decimalPart)
{
    return "";
}

#endregion