public void OperationButtonPress(string valueBtnOperation) { if (vmCalculation.FirstOperand == string.Empty || LastOperation == "=") { vmCalculation.FirstOperand = display; LastOperation = valueBtnOperation; } else { vmCalculation.SecondOperand = display; vmCalculation.Operation = lastOperation; vmCalculation.Calculation(vmCalculation.FirstOperand, vmCalculation.Operation, vmCalculation.SecondOperand); if (vmCalculation.SecondOperand != "0" && vmCalculation.Operation != "/") { FullExpression = vmCalculation.FirstOperand + " " + vmCalculation.Operation + " " + vmCalculation.SecondOperand + " " + "=" + vmCalculation.Result; } else { FullExpression = "Ділення на нуль"; } LastOperation = valueBtnOperation; Display = vmCalculation.Result; vmCalculation.FirstOperand = display; } newDisplayRequired = true; }