VB.Net Tutorial/GUI Applications/Application Exception
Application Exception
<source lang="vbnet">Imports System.Windows.Forms Public Class Form1
Inherits System.Windows.Forms.Form Public Sub New() MyBase.New() InitializeComponent() End Sub Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean) If disposing Then If Not (components Is Nothing) Then components.Dispose() End If End If MyBase.Dispose(disposing) End Sub Private components As System.ruponentModel.IContainer Friend WithEvents button4 As System.Windows.Forms.Button Friend WithEvents button3 As System.Windows.Forms.Button Friend WithEvents button2 As System.Windows.Forms.Button Friend WithEvents button1 As System.Windows.Forms.Button <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent() Me.button4 = New System.Windows.Forms.Button() Me.button3 = New System.Windows.Forms.Button() Me.button2 = New System.Windows.Forms.Button() Me.button1 = New System.Windows.Forms.Button() Me.SuspendLayout() " Me.button4.Location = New System.Drawing.Point(24, 127) Me.button4.Name = "button4" Me.button4.Size = New System.Drawing.Size(144, 23) Me.button4.TabIndex = 7 Me.button4.Text = "Show MessageBox" " Me.button3.Location = New System.Drawing.Point(24, 90) Me.button3.Name = "button3" Me.button3.Size = New System.Drawing.Size(144, 23) Me.button3.TabIndex = 6 Me.button3.Text = "Throw Exception" " Me.button2.Location = New System.Drawing.Point(24, 53) Me.button2.Name = "button2" Me.button2.Size = New System.Drawing.Size(144, 23) Me.button2.TabIndex = 5 Me.button2.Text = "Application.ExitThread" " "button1 " Me.button1.Location = New System.Drawing.Point(24, 16) Me.button1.Name = "button1" Me.button1.Size = New System.Drawing.Size(144, 23) Me.button1.TabIndex = 4 Me.button1.Text = "Application.Exit" " "Form1 " Me.AutoScaleBaseSize = New System.Drawing.Size(5, 13) Me.ClientSize = New System.Drawing.Size(192, 166) Me.Controls.AddRange(New System.Windows.Forms.Control() {Me.button4, Me.button3, Me.button2, Me.button1}) Me.Name = "Form1" Me.Text = "Applications" Me.ResumeLayout(False) End Sub Shared Sub App_Exit(ByVal sender As Object, ByVal e As EventArgs) System.Diagnostics.Debug.WriteLine("App_Exit") End Sub Shared Sub App_Idle(ByVal sender As Object, ByVal e As EventArgs) System.Diagnostics.Debug.WriteLine("App_Idle") End Sub Shared Sub App_ThreadingException(ByVal sender As Object, ByVal e As System.Threading.ThreadExceptionEventArgs) System.Diagnostics.Debug.WriteLine("App_ThreadException") Dim msg As String = "A problem has occurred in this application." & vbCrLf & vbCrLf & _ vbTab & e.Exception.Message & vbCrLf & vbCrLf & _ "Would you like to continue the application so that " & vbCrLf & _ "you can save your work?" Dim res As DialogResult = MessageBox.Show(msg, "Unexpected Error", MessageBoxButtons.YesNo) If res = System.Windows.Forms.DialogResult.Yes Then Exit Sub Application.Exit() End Sub Shared Sub DumpThreadID(ByVal name As String) System.Diagnostics.Debug.WriteLine(name & " thread id= " & System.AppDomain.GetCurrentThreadId().ToString()) End Sub Shared Sub DummyThreadStart() DumpThreadID("Dummy Thread") AddHandler Application.ThreadExit, New EventHandler(AddressOf App_ThreadExit) End Sub Shared Sub Main() AddHandler Application.ThreadException, New System.Threading.ThreadExceptionEventHandler(AddressOf App_ThreadingException) AddHandler Application.Idle, New EventHandler(AddressOf App_Idle) AddHandler Application.ThreadExit, New EventHandler(AddressOf App_ThreadExit) AddHandler Application.ApplicationExit, New EventHandler(AddressOf App_Exit) DumpThreadID("UI Thread") Dim dummythread As System.Threading.Thread = New System.Threading.Thread(New System.Threading.ThreadStart(AddressOf DummyThreadStart)) dummythread.Start() Application.Run(New Form1()) End Sub Shared Sub App_ThreadExit(ByVal sender As Object, ByVal e As EventArgs) System.Diagnostics.Debug.WriteLine("App_ThreadExit on thread id= " & System.AppDomain.GetCurrentThreadId().ToString()) End Sub Private Sub button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles button1.Click Application.Exit() End Sub Private Sub button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles button2.Click Application.ExitThread() End Sub Private Sub button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles button3.Click Throw New System.IO.FileLoadException() End Sub
End Class</source>
Catch Application Level Exception
<source lang="vbnet">Imports System.Drawing Imports System.IO Imports System.Windows.Forms Imports System.Math public class ApplicationLevelException
public Shared Sub Main Application.Run(New Form1) End Sub
End class
Public Class Form1
" Install the ThreadException event handler. Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load AddHandler Application.ThreadException, AddressOf Me.app_ThreadException End Sub " Catch a ThreadException event. Private Sub app_ThreadException(ByVal sender As Object, ByVal e As System.Threading.ThreadExceptionEventArgs) MessageBox.Show("Caught unhandled exception") End Sub " Throw an InvalidDataException. Private Sub btnThrow_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnThrow.Click Throw New InvalidDataException("Bad data! Bad!") End Sub " Call the OnThreadException method. Private Sub btnOnThreadException_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnOnThreadException.Click Application.OnThreadException(New InvalidDataException("Bad data! Bad!")) End Sub
End Class <Global.Microsoft.VisualBasic.rupilerServices.DesignerGenerated()> _ Partial Public Class Form1
Inherits System.Windows.Forms.Form "Form overrides dispose to clean up the component list. <System.Diagnostics.DebuggerNonUserCode()> _ Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean) If disposing AndAlso components IsNot Nothing Then components.Dispose() End If MyBase.Dispose(disposing) End Sub "Required by the Windows Form Designer Private components As System.ruponentModel.IContainer "NOTE: The following procedure is required by the Windows Form Designer "It can be modified using the Windows Form Designer. "Do not modify it using the code editor. <System.Diagnostics.DebuggerStepThrough()> _ Private Sub InitializeComponent() Me.btnThrow = New System.Windows.Forms.Button Me.btnOnThreadException = New System.Windows.Forms.Button Me.SuspendLayout() " "btnThrow " Me.btnThrow.Location = New System.Drawing.Point(26, 24) Me.btnThrow.Name = "btnThrow" Me.btnThrow.Size = New System.Drawing.Size(104, 24) Me.btnThrow.TabIndex = 2 Me.btnThrow.Text = "Throw" " "btnOnThreadException " Me.btnOnThreadException.Location = New System.Drawing.Point(162, 24) Me.btnOnThreadException.Name = "btnOnThreadException" Me.btnOnThreadException.Size = New System.Drawing.Size(104, 24) Me.btnOnThreadException.TabIndex = 3 Me.btnOnThreadException.Text = "OnThreadException" " "Form1 " Me.AutoScaleDimensions = New System.Drawing.SizeF(6.0!, 13.0!) Me.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font Me.ClientSize = New System.Drawing.Size(292, 73) Me.Controls.Add(Me.btnThrow) Me.Controls.Add(Me.btnOnThreadException) Me.Name = "Form1" Me.Text = "CatchThreadException" Me.ResumeLayout(False) End Sub Friend WithEvents btnThrow As System.Windows.Forms.Button Friend WithEvents btnOnThreadException As System.Windows.Forms.Button
End Class</source>