Visual basic less than 0 - vb.net

Question

Im trying to make a program that when i put a value less than 0, in a label something like "
negative numbers cant be used i have this
Public Class Form1 'Sebastian roman. Perimeter, 10/1/2014
Private Sub btnCalculate_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnCalculate.Click
Try
Dim intSide1 As Integer = txtSide1.Text
Dim intSide2 As Integer = txtSide2.Text
Dim intSide3 As Integer = txtSide3.Text
Dim intSide4 As Integer = txtSide4.Text
Dim intTotal As Integer = intSide1 + intSide2 + intSide3 + intSide4
lblMessage.Text = intTotal.ToString("#,###.##")
Catch ex As Exception
MessageBox.Show("Incorrect Input. Enter a numeric value.")
End Try
End Sub
End Class
Yes i have to use the try catch method and i need help for this

Answer 1

This sounds an awful lot like homework, but you really need to convert your integers properly and then perform actual comparisons.
Public Class Form1 'Sebastian roman. Perimeter, 10/1/2014
Private Sub btnCalculate_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnCalculate.Click
Try
' Relies on the GetIntegerInput method to throw exceptions
' for invalid entries
Dim intSide1 As Integer = GetIntegerInput(txtSide1.Text)
Dim intSide2 As Integer = GetIntegerInput(txtSide2.Text)
Dim intSide3 As Integer = GetIntegerInput(txtSide3.Text)
Dim intSide4 As Integer = GetIntegerInput(txtSide4.Text)
Dim intTotal As Integer = intSide1 + intSide2 + intSide3 + intSide4
lblMessage.Text = intTotal.ToString("#,###.##")
Catch ex As Exception
MessageBox.Show(ex.Message)
End Try
End Sub
Private Function GetIntegerInput(ByVal input as String) As Integer)
Dim returnValue as Integer
' Will attempt a proper try parse. AndAlso will short circuit
' the comparison so a failure in TryParse will not perform the
' the second evaluation. In either case, an actual exception is
' thrown with your invalid numeric message
If (Not Int32.TryParse(input, returnValue) AndAlso returnValue < 0) Then
Throw New ArgumentException("Incorrect input. Enter a proper numeric value.")
End If
Return returnValue
End Function
End Class

Answer 2

Well a integer can be negative...
Private Sub btnCalculate_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnCalculate.Click
Try
Dim intSide1 As Integer = txtSide1.Text
Dim intSide2 As Integer = txtSide2.Text
Dim intSide3 As Integer = txtSide3.Text
Dim intSide4 As Integer = txtSide4.Text
Dim intTotal As Integer = intSide1 + intSide2 + intSide3 + intSide4
lblMessage.Text = intTotal.ToString("#,###.##")
//New code
if intSide1 < 0 or intSide2 < 0 or intSide3 < 0 intSide4 < 0 Then
MessageBox.Show("Incorrect Input. Negative number not valid")
end if
Catch ex As Exception
MessageBox.Show("Incorrect Input. Enter a numeric value.")
End Try
End Sub