Hello, I've been trying to create a function to calculate and return the total payment. RadioDay is a radio button with value of 7 while RadioHour is 70. Somehow I am getting InvalidCastException "Conversion from string "" to type 'Integer' is not valid." from the part where I want to convert user inputs from textbox "txtByHour" and "txtByDay" into integer value. Any help is greatly appreciated.
Function calcRate() As Integer 'calculate and return total payment for car Dim total, byHour, byDay As Integer byHour = CInt(txtByHour.Text) byDay = CInt(txtByDay.Text) If byHour > 24 Then 'making sure the user does not input more than 24 hours MessageBox.Show("Please put a number between 1 to 24") End If If RadioDay.Checked Then total = byHour * 7 ElseIf RadioHour.Checked Then total = byDay * 70 End If Return total End Function