Error Handling

Error handling merupakan suatu prosedur untuk menampilkan kesalahan pada proses ataupun input data program.

1. on error goto
Format penulisannya yaitu:
On Error GoTo   program_label

Contoh:
Masukkan 2 buah textbox, 2 buah label dan 1 buah button, kemudian ketikkan code berikut:
Public Class Form1

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim firstNum, secondNum As Double
        On Error GoTo error_handler
        firstNum = TextBox1.Text
        secondNum = TextBox2.Text
        Label4.Text = firstNum / secondNum
        Exit Sub
error_handler:
        Label4.Text = "Error"
        Label5.Visible = True
        Label5.Text = "Salah satu data inputan bukan berupa angka! Coba lagi!"
    End Sub

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Label5.Visible = False
    End Sub

End Class

2. try.. catch.. end try
Format penulisannya:

Try
statements
Catch exception_variable as Exception
statements to deal with exceptions
End Try

Contoh:
Masukkan 2 buah textbox, 2 buah label dan 1 buah button, kemudian ketikkan code berikut:
Public Class Form1

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Label5.Visible = False
        Dim firstNum, secondNum, answer As Double
        Try
            firstNum = TextBox1.Text
            secondNum = TextBox2.Text
            answer = firstNum / secondNum
            Label4.Text = answer
        Catch ex As Exception
            Label4.Text = "Error"
            Label5.Visible = True
            Label5.Text = " One of the entries is not a number! Try again!"
        End Try
    End Sub

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Label5.Visible = False
    End Sub

End Class

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