com.mendix.webui.WebUIException: Exception while executing runtime operation at com.mendix.webui.actions.client.RuntimeOperationAction.$anonfun$apply$1(RuntimeOperationAction.scala:60) Caused by: com.mendix.modules.microflowengine.MicroflowException: Failed to evaluate expression, error occurred on line 1, character 1 addDays($TrainingEvent/StartDate,$course/Duration) ^ at MyFirstModule.OCH_TrainingEvent_CalculateEndDate (Change : 'Change 'TrainingEvent' (EndDate)') Advanced stacktrace: at com.mendix.languages.mxexpressions.MxExpressionImpl.evaluate(MxExpressionImpl.scala:32) Caused by: com.mendix.languages.expressions.ExpressionException: Incorrect arguments for function addDays: null, 1 at com.mendix.languages.expressions.FunctionCallExpr$$anonfun$error$1.applyOrElse(FunctionCallExpr.scala:35)
The expression is correct, the error is with an empty value.
$TrainingEvent/StartDate is null. So either the StartDate attribute or $TrainingEvent entity is empty.
It is probably worth adding some checks for empty before you call addDays.
I hope this helps.
which i removed space error was removed : Note: Spaces, tabs, and returns are ignored in microflow expressions, so add as much formatting as you’d like to make your expressions more readable.