Question

I am a beginner in VB.NET and I would like to know how do I handle the errors that may appear from the user of my program. For example, I have an triangle area program in wich I ask the user of the program to insert the length of the base and height of the triangle in a textbox. But what if he inserts a letter or something else, like a sign….my program will crash…

I know that one method would be to use On Error GoTo but I don’t know how. If maybe you can direct me to some link or you could explain how do I handle errors, I would be grateful. Maybe you can even show me other ways to avoid errors from the user input.

This is my small program so far:

Private Sub Button1_Click(ByVal sender As Object, ByVal e As EventArgs)
                Handles Button1.Click

    Dim , Height, ARIA As Integer

    Base = TextBox1.Text
    Height = TextBox2.Text
    ARIA =  Base * Height / 2
    TextBox3.Text = ARIA

End Sub

Answer 1

Your homework should look like this…

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
    Dim Base, Height, ARIA As Integer
    Try
        Base = TextBox1.Text
        Height = TextBox2.Text
        ARIA = Base * Height / 2
        TextBox3.Text = ARIA
    Catch ex As Exception
        MessageBox.Show("Please enter a number")
    End Try
End Sub