Question

I am currently using ncalc library to do several evaluation and get the result out of it.

Right now I have found a problem where if I have a price in the format “1,234.01” it will fail to evaluate my expression.

The current workaround I’ve used was to remove the , but I was wondering if there is way to evaluate a currency without having to remove the , for example:

decimal price = 0;
if (!decimal.TryParse(iPrice.Text, out price))
{
    MessageBox.Show("Price is not formatted correctly...");
    return;
}

decimal currency = 0;
if (!decimal.TryParse(iCurrency.Text, out currency))
{
    MessageBox.Show("Currency is not formatted correctly...");
    return;
}

string formula = iFormula.Text.Replace("Price", price.ToString("n2")).Replace("Currency", currency.ToString("n2"));
Expression exp = new Expression(formula);
exp.Evaluate();

Evaluate fails because of the , from my price where if I remove it, it works just fine.

Sample of the formula:

(((Price+12,9)+((Price+12,9)*0,05)+(((Price+12,9)+((Price+12,9)*0,05))*0,029)+0,45)*Currency)

Stacktrace as requested:

NCalc.EvaluationException was unhandled
  Message=mismatched input ',' expecting ')' at line 1:4
mismatched input ',' expecting ')' at line 1:20
mismatched input ',' expecting ')' at line 1:43
mismatched input ',' expecting ')' at line 1:59
missing EOF at ')' at line 1:77
  Source=NCalc
  StackTrace:
       at NCalc.Expression.Evaluate()

Answer 1

Your question is still unclear to me, but I suspect you can fix this just by changing the format you’re using when replacing. Change this:

string formula = iFormula.Text.Replace("Price", price.ToString("n2")) 
                              .Replace("Currency", currency.ToString("n2"));

to this:

string formula = iFormula.Text.Replace("Price", price.ToString("f2")) 
                              .Replace("Currency", currency.ToString("f2"));

That will use the “fixed point” format instead of the “number” format. You won’t get grouping. Note that grouping isn’t part of the number itself – it’s part of how you format a number.

I’d also be tempted to specify the invariant culture explicitly, by the way.

As an aside: I haven’t used NCalc myself, but if it’s really forcing you to specify the numeric values in an expression as text, that sounds pretty poor. I’d expect some sort of parameterization (as per most SQL providers, for example) which should make all of this go away.