Im trying to make a program which basically performs unit conversion.
I have basically made two text boxes, one for the S.I. Units and the other for British Units. The general idea is that when i input any number in the S.I. Unit text box, it should display the answer in British Unit text Box and similiarly if i input any number in British Unit Textbox, the answer should be displayed in S.I.Unit textbox. Now the problem lies here that the code that i created is by using if else. now the compiler automatically gives me the correct result in the British box when i input the value in the s.i. unit box, but when i input the value in the british text box, it gives an error that :
"An unhandled exception of type 'System.InvalidCastException' occurred in Microsoft.VisualBasic.dll
Additional information: Conversion from string "" to type 'Double' is not valid."
Heres the part of the code.
Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click Dim p As String = "Pressure" Dim d As String = "Density" Dim t As String = "Temperature" Dim f As String = "Force" Dim si As Double = siubox.Text Dim pi As Double = bubox.Text Dim a As Double = 0.0208865 'for pressure si to british Dim b As Double = 47.73 'for pressure british to si While ComboBox1.Text = p If siubox.Text = si Then bubox.Text = a * si ElseIf bubox.Text = pi Then siubox.Text = pi * b End If Exit While End While End Sub
Will appreciate the help. Thanks.