The following code example displays two forms and exits the application when both forms are closed. When the application starts and exits, the position of each form is remembered. This example demonstrates using the UserAppDataPath property to store application data for the user.
The class MyApplicationContext inherits from ApplicationContext and keeps track when each form is closed, and exits the current thread when they both are. The class stores the positions of each form for the user. The form position data is stored in a file titled Appdata.txt that is created in the location determined by UserAppDataPath. The Main method calls Application.Run(context) to start the application given the ApplicationContext.
This code is an excerpt from the example shown in the ApplicationContext class overview. Some code is not shown for the purpose of brevity. See ApplicationContext for the whole code listing.
Public Sub New()
MyBase.New()
formCount = 0
' Handle the ApplicationExit event to know when the application is exiting.
AddHandler Application.ApplicationExit, AddressOf OnApplicationExit
Try
' Create a file that the application will store user specific data in.
userData = New FileStream(Application.UserAppDataPath + "\appdata.txt", FileMode.OpenOrCreate)
Catch e As IOException
' Inform the user that an error occurred.
MessageBox.Show("An error occurred while attempting to show the application." + _
"The error is:" + e.ToString())
' Exit the current thread instead of showing the windows.
ExitThread()
End Try
' Create both application forms and handle the Closed event
' to know when both forms are closed.
form1 = New AppForm1()
AddHandler form1.Closed, AddressOf OnFormClosed
AddHandler form1.Closing, AddressOf OnFormClosing
formCount = formCount + 1
form2 = New AppForm2()
AddHandler form2.Closed, AddressOf OnFormClosed
AddHandler form2.Closing, AddressOf OnFormClosing
formCount = formCount + 1
' Get the form positions based upon the user specific data.
If (ReadFormDataFromFile()) Then
' If the data was read from the file, set the form
' positions manually.
form1.StartPosition = FormStartPosition.Manual
form2.StartPosition = FormStartPosition.Manual
form1.Bounds = form1Position
form2.Bounds = form2Position
End If
' Show both forms.
form1.Show()
form2.Show()
End Sub
Private Sub OnApplicationExit(ByVal sender As Object, ByVal e As EventArgs)
' When the application is exiting, write the application data to the
' user file and close it.
WriteFormDataToFile()
Try
' Ignore any errors that might occur while closing the file handle.
userData.Close()
Catch
End Try
End Sub
private MyApplicationContext() {
formCount = 0;
// Handle the ApplicationExit event to know when the application is exiting.
Application.ApplicationExit += new EventHandler(this.OnApplicationExit);
try {
// Create a file that the application will store user specific data in.
userData = new FileStream(Application.UserAppDataPath + "\\appdata.txt", FileMode.OpenOrCreate);
} catch(IOException e) {
// Inform the user that an error occurred.
MessageBox.Show("An error occurred while attempting to show the application." +
"The error is:" + e.ToString());
// Exit the current thread instead of showing the windows.
ExitThread();
}
// Create both application forms and handle the Closed event
// to know when both forms are closed.
form1 = new AppForm1();
form1.Closed += new EventHandler(OnFormClosed);
form1.Closing += new CancelEventHandler(OnFormClosing);
formCount++;
form2 = new AppForm2();
form2.Closed += new EventHandler(OnFormClosed);
form2.Closing += new CancelEventHandler(OnFormClosing);
formCount++;
// Get the form positions based upon the user specific data.
if (ReadFormDataFromFile()) {
// If the data was read from the file, set the form
// positions manually.
form1.StartPosition = FormStartPosition.Manual;
form2.StartPosition = FormStartPosition.Manual;
form1.Bounds = form1Position;
form2.Bounds = form2Position;
}
// Show both forms.
form1.Show();
form2.Show();
}
private void OnApplicationExit(object sender, EventArgs e) {
// When the application is exiting, write the application data to the
// user file and close it.
WriteFormDataToFile();
try {
// Ignore any errors that might occur while closing the file handle.
userData.Close();
} catch {}
}
MyApplicationContext()
{
formCount = 0;
// Handle the ApplicationExit event to know when the application is exiting.
Application::ApplicationExit += gcnew EventHandler( this, &MyApplicationContext::OnApplicationExit );
try
{
// Create a file that the application will store user specific data in.
userData = gcnew FileStream( String::Concat( Application::UserAppDataPath, "\\appdata.txt" ),FileMode::OpenOrCreate );
}
catch ( IOException^ e )
{
// Inform the user that an error occurred.
MessageBox::Show( "An error occurred while attempting to show the application. The error is: {0}", dynamic_cast<String^>(e) );
// Exit the current thread instead of showing the windows.
ExitThread();
}
// Create both application forms and handle the Closed event
// to know when both forms are closed.
form1 = gcnew AppForm1;
form1->Closed += gcnew EventHandler( this, &MyApplicationContext::OnFormClosed );
form1->Closing += gcnew CancelEventHandler( this, &MyApplicationContext::OnFormClosing );
formCount++;
form2 = gcnew AppForm2;
form2->Closed += gcnew EventHandler( this, &MyApplicationContext::OnFormClosed );
form2->Closing += gcnew CancelEventHandler( this, &MyApplicationContext::OnFormClosing );
formCount++;
// Get the form positions based upon the user specific data.
if ( ReadFormDataFromFile() )
{
// If the data was read from the file, set the form
// positions manually.
form1->StartPosition = FormStartPosition::Manual;
form2->StartPosition = FormStartPosition::Manual;
form1->Bounds = form1Position;
form2->Bounds = form2Position;
}
// Show both forms.
form1->Show();
form2->Show();
}
void OnApplicationExit( Object^ /*sender*/, EventArgs^ /*e*/ )
{
// When the application is exiting, write the application data to the
// user file and close it.
WriteFormDataToFile();
try
{
// Ignore any errors that might occur while closing the file handle.
userData->Close();
}
catch ( Exception^ )
{
}
}
private: