string to Currency format, with no periods (or commas)
value = Convert.ToDecimal(value).ToString("C2");

var stringValue = Convert.ToDecimal(value).ToString("$0.00");

var formatInfo = (NumberFormatInfo)CultureInfo.CurrentCulture.NumberFormat.Clone();
formatInfo.CurrencyGroupSeparator = string.Empty;

var stringValue = Convert.ToDecimal(value).ToString("C", formatInfo);

var formatInfo = (System.Globalization.NumberFormatInfo)CultureInfo.CurrentCulture.NumberFormat.Clone();
formatInfo.CurrencyGroupSeparator = ""; // remove the group separator
Console.WriteLine(2.ToString("C", formatInfo));
Console.WriteLine(4.ToString("C", formatInfo));
Console.WriteLine(1000.ToString("C", formatInfo));

public static class MyExtensions
{
    public static string GetMoney(this decimal value, bool displayCurrency = false, bool displayPeriods = true)
    {
        string ret = string.Format("{0:C}", value).Substring(displayCurrency ? 0 : 1);
        if (!displayPeriods)
        {
            ret = ret.Replace(",", string.Empty);
        }
        return ret;
    }
}

decimal test = 40023.2345M;
string myValue = test.GetMoney(displayCurrency:true, displayPeriods:false);`