Ncalc Exception Handling

Exception handling helps you deal with any unexpected or exceptional situations that occur when a program is running. You can use the try, catch, and finally keywords to try actions that may not succeed, to handle failures, and to clean up resources afterward.

When the expression has a syntax error, the evaluation will throw an EvaluationException.

public static void Example1()
{
    try
    {
        string expression = "[x] + [y] +";

        Expression evaluator = new Expression(expression);
        evaluator.Parameters["x"] = 3;
        evaluator.Parameters["y"] = 4;

        Console.WriteLine("{0} = {1}", expression, evaluator.Evaluate());
    }
    catch (EvaluationException e)
    {
        Console.WriteLine("Error catched: " + e.Message);
    }
}

You can also detect syntax errors before evaluating the expression by calling the HasErrors() method, as shown below.

public static void Example2()
{
    try
    {
        string expression = "[x] + [y] +";

        Expression evaluator = new Expression(expression);
        evaluator.Parameters["x"] = 3;
        evaluator.Parameters["y"] = 4;

        if (!evaluator.HasErrors())
        {
            Console.WriteLine("{0} = {1}", expression, evaluator.Evaluate());
        }
        else
        {
            Console.WriteLine(evaluator.Error);
        }
        
    }
    catch (EvaluationException e)
    {
        Console.WriteLine("Error catched: " + e.Message);
    }
}