how to handle null in IF expression of NCALC

I have a complex NCALC if expression which goes something like this:

if ( {0} == null || {1} == 0 ,{2} * ({3} * {4} + {5}), ({2} * ({3} * {4} + {5}))/{1})

This gives me some unexpected error such as below:

missing ')' at '==' at line 1:6

missing EOF at 'UnsetValue' at line 1:37

What the issue here- i couldnt find if NCALC supports null. if it does, then what could be wrong in the above expression. Kindly help!!

My experience has been ncalc does not support null. But you can write your own function to evaluate if the parameter passed in has a value and return a true / false.

To do this, wire up an EvaluateFunction. (small example below)

var exp = new NCalc.Expression("if(HASVALUE([variable], [variable] *2, 0)")
exp.Parameters["variable"] = 2;
exp.EvaluateFunction += SpecRule_EvaluateFunction;

private void SpecRule_EvaluateFunction(string name, NCalc.FunctionArgs args)
{
   switch (name.ToUpper())
   {
       case "HASVALUE":
          if (args.Parameters.Length < 1)
               throw new ArgumentException("IsNull must have at least 1 argument");
    
             args.Result = args.Parameters[0].Parameters.Values.FirstOrDefault() != null;
    
             break;
    }
}