how do i stop system stack overflow in visual basic?

Question

I'm working on an application designed to convert between different number systems. Its operation involves users inputting a value in one base number system, after which the remaining three text boxes will automatically display the equivalent values in the other number systems. However, I've encountered a stack overflow error in my code. Specifically, when I attempt to add code to the oct2_textbox, the error occurs. I'm unsure how to resolve this issue.

Imports System.ComponentModel
Imports System.Windows.Forms.VisualStyles.VisualStyleElement

Public Class Form1
    Private Sub Label3_Click(sender As Object, e As EventArgs)

    End Sub

    Private Sub TextBox5_TextChanged(sender As Object, e As EventArgs)

    End Sub



    Private Sub oct_KeyPress(sender As Object, e As KeyPressEventArgs)

        If Not (e.KeyChar >= "0"c AndAlso e.KeyChar <= "7"c OrElse Char.IsControl(e.KeyChar)) Then
            e.Handled = True
        End If
    End Sub

    Private Sub HEX_TextChanged(sender As Object, e As EventArgs) Handles HEX.TextChanged

        Dim HEX_num As Integer
        If Integer.TryParse(HEX.Text, System.Globalization.NumberStyles.HexNumber, Nothing, HEX_num) Then

            oct2.Text = Convert.ToString(HEX_num, 8)
            DECDEC.Text = Convert.ToString(HEX_num, 10)

            bin.Text = Convert.ToString(HEX_num, 2)

        End If
        bin.Text = bin.Text.ToString()

    End Sub
    Private Sub HEX_KeyPress(sender As Object, e As KeyPressEventArgs) Handles HEX.KeyPress
        ' Remove the event handler temporarily
        RemoveHandler HEX.KeyPress, AddressOf HEX_KeyPress

        Dim inputChar As Char = Char.ToUpper(e.KeyChar)

        If Not (Char.IsDigit(inputChar) OrElse
            (inputChar >= "A"c AndAlso inputChar <= "F"c) OrElse
            Char.IsControl(e.KeyChar)) Then
            e.Handled = True
        End If

        ' Reattach the event handler
        AddHandler HEX.KeyPress, AddressOf HEX_KeyPress
    End Sub


    Private Sub DECDEC_TextChanged(sender As Object, e As EventArgs) Handles DECDEC.TextChanged
        Dim decdec_num As Integer
        If Integer.TryParse(DECDEC.Text, decdec_num) Then
            oct2.Text = Convert.ToString(decdec_num, 8)
            HEX.Text = Convert.ToString(decdec_num, 16)
            bin.Text = Convert.ToString(decdec_num, 2)
        End If
    End Sub


    Private Sub DECDEC_KeyPress(sender As Object, e As KeyPressEventArgs) Handles DECDEC.KeyPress

        If Not (Char.IsDigit(e.KeyChar) OrElse Char.IsControl(e.KeyChar)) Then
            e.Handled = True
        End If
    End Sub

    Private Sub bin_TextChanged(sender As Object, e As EventArgs) Handles bin.TextChanged
        ' Remove the event handler temporarily
        RemoveHandler bin.TextChanged, AddressOf bin_TextChanged

        Dim bin_str As String = bin.Text.Trim()
        If Not String.IsNullOrEmpty(bin_str) AndAlso bin_str.All(Function(c) c = "0" OrElse c = "1") Then
            Dim bin_num As Integer = Convert.ToInt32(bin_str, 2)
            DECDEC.Text = bin_num.ToString()
            HEX.Text = Convert.ToString(bin_num, 16)
            oct2.Text = Convert.ToString(bin_num, 8)
        End If

        ' Reattach the event handler
        AddHandler bin.TextChanged, AddressOf bin_TextChanged
    End Sub


    Private Sub bin_KeyPress(sender As Object, e As KeyPressEventArgs) Handles bin.KeyPress
        ' Remove the event handler temporarily
        RemoveHandler bin.KeyPress, AddressOf bin_KeyPress

        If Not (e.KeyChar = "0"c OrElse e.KeyChar = "1"c OrElse Char.IsControl(e.KeyChar)) Then
            e.Handled = True
        End If

        ' Reattach the event handler
        AddHandler bin.KeyPress, AddressOf bin_KeyPress
    End Sub


    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        oct2.Text = ""
        HEX.Text = ""
        DECDEC.Text = ""
        bin.Text = ""


    End Sub

    Private Sub GroupBox4_Enter(sender As Object, e As EventArgs) Handles GroupBox4.Enter

    End Sub

    Private Sub oct2_TextChanged(sender As Object, e As EventArgs) Handles oct2.TextChanged
        ' Remove the event handler temporarily
        RemoveHandler oct2.TextChanged, AddressOf oct2_TextChanged

        Dim oct2_num As Integer
        If Integer.TryParse(oct2.Text, oct2_num) Then
            DECDEC.Text = Convert.ToString(oct2_num, 10)
            HEX.Text = Convert.ToString(oct2_num, 16)
            bin.Text = Convert.ToString(oct2_num, 2)
        End If

        ' Reattach the event handler
        AddHandler oct2.TextChanged, AddressOf oct2_TextChanged
    End Sub


End Class

I want a dynamic and responsive system that automatically convert when a value is changed.

Answer 1

You can use a guard to prevent recursive calls

Private m_updating As Boolean

Then in the TextChanged event handlers check, set and reset the guard. Here HEX_TextChanged as an example

Private Sub HEX_TextChanged(sender As Object, e As EventArgs) Handles HEX.TextChanged
    If Not m_updating Then
        m_updating = True
        Try
            ' TODO: put your conversion and updating logic here.
            ' (Don't remove or add event handlers)
        Finally
            m_updating = False
        End Try
    End If
End Sub

The Try-Finally statement makes sure the guard is reset in any case, even if an exception should occur or the code was left prematurely with a Return-statement.

Implement this in HEX_TextChanged, DECDEC_TextChanged, bin_TextChanged and oct2_TextChanged.

The KeyPress methods do not require a guard or removing/adding the event handlers, because they are only filtering keys and do not update other TextBoxes (this is what raises the TextChanged events and caused the recursive calls).

You can also slightly simplify them by directly assigning the Boolean value:

Private Sub bin_KeyPress(sender As Object, e As KeyPressEventArgs) Handles bin.KeyPress
    e.Handled = Not (e.KeyChar = "0"c OrElse e.KeyChar = "1"c OrElse
        Char.IsControl(e.KeyChar))
End Sub

I didn't check whether your actual filtering or conversion logic is correct.