c# ncalc - line 1:1 missing EOF at 'x'

Question

Im playing around with a genetic algorithm for solving eqvations. So I've found this lib called NCAL which seems to be a nice way to go.

So I've tried to generate som random strings that will become NCALC Expressions like this:

    private Expression getRandomExpression(int i)
    {
        string expression = ""; ;
        double nr = random.NextDouble() * random.Next(100);
        int sign = 1;

        if (random.Next(2) > 0)
        {
            sign = -1;
        }
        Console.WriteLine("sign: " + sign + " i: " + i);
        switch (i)
        {
            case 1:
                expression = (sign.ToString() + "*" + nr.ToString() + "x");
                break;
            case 2:
                expression = (sign.ToString() + nr.ToString() + "/x");
                break;
            case 3:
                expression = (sign.ToString() + "x/" + nr.ToString());
                break;
            case 4:
                expression = (sign.ToString() + "Pow(x," + nr.ToString()+")");
                break;
            default:
                expression = (sign.ToString() + "*" + nr.ToString());
                break;
        }

        return new Expression(expression);
    }

And then I want to loop over these elements and check the sum against my goalfunction, like this:

public double calculateFitness(double[] goalFunction)
    {
        double fitness = 0.0;

        for (int i = 1; i < goalFunction.Length; i++)
        {
            foreach (var element in genome)
            {
                try
                {
                    element.Parameters["x"] = i;
                    var value = (double)element.Evaluate();
                    fitness += Math.Abs(goalFunction.ElementAt(i) - value);
                }catch(Exception ex)
                {
                    throw ex;
                }
            }     
        }

        return fitness;
    }

Seems easy but I keep getting this exception saying "line 1:1 missing EOF at 'x'". Any suggestions on how to solve this? Or easier ways to go. :) I want to be able to find a equation representing the goalfunction.

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