I tried this out and I am getting the same results. But the results I get are very strange. 

If I tried this in the Form_Load event, I get the same results as you.

If I create an UltraCalcManager and place it on the form and then use a TextBox control for the formula result, it works fine.

Using a CalcManager that is on the form with the Calculate method does not work inside the Form_Load, but it works later on if I use a button_click event.

So I think the problem is that the code you have here is trying to perform operations on the CalcManager synchonrously. You are expecting that when you add a new NamedReference to the NamedReferences collection that the NamedReference is immediately available for use in a formula. But this is not the case, by default. It works okay when your formula is '75' because that's a literal value and requires no extra calculation. But "null()" is a function. I also tried the same thing using "sum(5, 5)" and got the same results, so it's not just null that is a problem, it's any function. 

Anyway, if I am right, then the solution is simply this:

            const string formula = "IF( ISNULL( [test] ), 100, [test] )";

            var ultraCalcManager1 = new UltraCalcManager();
            ultraCalcManager1.CalcFrequency = CalcFrequency.Synchronous;

            ultraCalcManager1.NamedReferences.Add("test", "75");

            var result = ultraCalcManager1.Calculate(formula);

            ultraCalcManager1.NamedReferences.Clear();
            ultraCalcManager1.NamedReferences.Add("test", "null()");

            result = ultraCalcManager1.Calculate(formula);    

I tried this out and it works fine for me.

Hello Torx,

I`m not sure that I understand well your scenario and requirements, but maybe one possible approach could be if you are using formula:

ultraGrid1.DisplayLayout.Bands[0].Columns["C"].Formula = "if([B]=null() , 0 , [B])";

Please take a look at the attached sample for more details. About NamedReferences, please take a look at:

http://help.infragistics.com/Help/NetAdvantage/WinForms/2013.1/CLR4.0/html/WinCalcManager_NamedReferences_Formula.html 

http://help.infragistics.com/Help/NetAdvantage/WinForms/2012.2/CLR4.0/html/Win_WinCalcManager_Using_WinCalcManager.html 

Another possible approach could be if you create your own custom formula. Please take a look at that forum thread: http://ko.infragistics.com.es/community/forums/t/80164.aspx?PageIndex=2  There you could find few samples.

Let me know if you have any qustions.

Regards