I have written an application that allows my users to apply an unbound column to the grid. Then using formula builder dialogue apply a formula to perform thier own calculations in the grid on existing data. When they try to add a summary it will only allow count, max and min. I am assuming this is because when adding the unbound column for the formula I am letting the grid decide the data type to use (found this trick in another post that described a unhandled exception scenario in the calc engine). If I assign the data type (System.Double) everything works fine. Summaries work everything seems great until you try to apply a formula in that column that manipulates string data and returns a string. There is an unhandled exception somewhere in the calc engine that kills the application as per the first article I found that told me about the trick how to not get the unhandled exception. Typical setup of the code is as follows:
calcMan.SuspendCalc();
CreateColumnReturn newColumn = CreateFormulaColumn();
if (newColumn.Created)
{
gridQueryData.CalcManager = calcMan;
ShowFormulaBuilderDialog(newColumn.NewColumn);
}
calcMan.ResumeCalc();
Hi,
Well... if you have a column in the grid whose DataType is double, you cannot have a formula in that column that returns a string - the value of the cell must be a double.
It probably should not be crashing the application with an unhandled exception, but there's no way this can work the way you want it to.
If the field is a double and you need to calculate a numeric summary, then why is the formula returning a string? Is this just an error on the part of the user?
Absolutely! I was doing a "what if" scenario knowing what users will do sometimes. Is there a way to examine the possible outcome of the formula before turning on the calcmanager again? Maybe I can intercept this and remove the formula or repop the editor with a message about invalid formula for column type. I was trying to catch any exception thrown by calmanager but none of the provided exceptions I have found as well as a generic exception catch block will handle this error.
Hi Lewis,
No, there's no way for you to trap what Type the results of a formula might be. Or at least no reasonable way. You might examine the formula and try to figure it out yourself in code, but that's really not feasible.
I guess one thing you might be able to do is use a DataFilter. A DataFilter on the grid column's Editor will theoretically allow you to intercept the value from the CalcManager and examine it before it get to the grid. So if it's a string, you could change it to a 0 or a null or something that the column can handle. I say "theoretically" because I have not tried this out, but I think it should work.
Thanks Mike,
I created a case with developer support. The grid should at least provide a trappable error in the event the user just does not understand what they are doing. Thanks for your feed back!
I tend to agree with you there. The result should probably be to return the error code rather than raising an exception.