By default, the EvaluateSelection property is True. While the  EvaluateSelection property is True, the control evaluates the selection ( if available ), rather than entire text. If the EvaluateSelection property is False, the control evaluates the entire text. The EvaluationText property specifies the values for variables in the expression to be evaluated ( per line ). The EvaluationResult property specifies the result for each evaluation ( line ). The IsValid property indicates whether the control's expression is valid/syntactically correct. Use the Evaluate property to get the result of evaluation of the control's expression.