In a program, a modal workflow is a mode of operation in which a particular task or feature must be completed before the user can proceed to other tasks or features. This is typically implemented by displaying a modal window or dialog box that requires user interaction before continuing.
Modal workflows are often used when users must complete specific tasks or provide required information. For example, a modal workflow might prompt users to save work before closing a document, or enter login credentials before accessing restricted areas.
Modal workflows help guide users through specific steps or highlight important actions. However, if overused, they can disrupt workflow.
In web applications, supporting modal workflow means:
Suspending server-side code execution
Waiting for user input
Resuming execution with received user information
While straightforward in desktop applications, this becomes challenging in web applications where code executes on the server and the UI runs asynchronously on different machines.
Modal Workflow
The code and images below demonstrate how Wisej.NET handles modal code execution:
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
If MessageBox.Show("Are you sure?", buttons:=MessageBoxButtons.YesNo) = DialogResult.Yes Then
Me.Button1.BackColor = Color.Green
Me.Button1.Text = "You selected: Yes!"
End If
End Sub
The server code suspends, waiting for user choice. After clicking Yes or No on the client-side, the server code resumes exactly where it was suspended.
Wisej.NET supports:
Nested modal states
Custom DialogResult values
Control references in modal dialogs
User input data access
Modal Dialogs
Modal workflow works for MessageBox and forms (dialog boxes) with any type of control, data binding, and code-behind. The example above, modified to use a modal dialog, looks like this:
void button1_Click(object sender, EventArgs e)
{
using (new dialog = new EnterCustomerAddress())
{
if (dialog.ShowDialog(this) == DialogResult.OK)
{
AlertBox.Show(dialog.textBoxAddress.Text + " " + dialog.textBoxState.Text);
}
}
}
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Using dialog As New EnterCustomerAddress()
If dialog.ShowDialog(Me) = DialogResult.OK Then
AlertBox.Show(dialog.textBoxAddress.Text + " " + dialog.textBoxState.Text)
End If
End Using
End Sub
Regular modal dialogs or MessageBox controls suspend the current thread while waiting for user input. By default the system handles about 32,000 threads. While suspended, threads use no CPU time.
Async Modal Dialogs
Wisej.NET fully supports the async/await programming pattern for modal dialogs.
Using the await keyword, a modal dialog can wait for closure without thread suspension. Simply use the "Async" version of the ShowDialog method.
The async version of MessageBox is MessageBox.ShowAsync(...).
void async button1_Click(object sender, EventArgs e)
{
using (new dialog = new EnterCustomerAddress())
{
if (await dialog.ShowDialogAsync(this) == DialogResult.OK)
{
AlertBox.Show(dialog.textBoxAddress.Text + " " + dialog.textBoxState.Text);
}
}
}
Private Async Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Using dialog As New EnterCustomerAddress()
If Await dialog.ShowDialogAsync(Me) = DialogResult.OK Then
AlertBox.Show(dialog.textBoxAddress.Text + " " + dialog.textBoxState.Text)
End If
End Using
End Sub
Asynchronous modal dialogs or MessageBox controls don't use any threads while waiting for user input.
Custom Modal State
You can implement modal behavior and wait for user input without using modal dialogs or MessageBox controls. Wisej.NET provides Application.DoModal(component) for this purpose.
For example, the PropertyGrid uses Application.DoModal() to suspend code flow while waiting for dropdown selection box closure. Use Application.EndModal(component, result) to terminate the last modal state - modal states are stacked.
// Open the combo box drop down list and wait
// for the user to select an item or close the combo box.
private void button1_Click(object sender, EventArgs e)
{
this.comboBox1.DroppedDown = true;
this.comboBox1.DropDownClosed += ComboBox1_DropDownClosed;
this.comboBox1.SelectedIndexChanged += ComboBox1_SelectedIndexChanged;
// wait for the user to either pick an item or close the drop down.
var result = Application.DoModal(this.comboBox1);
// code execution will resume here.
}
private void ComboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
this.comboBox1.DropDownClosed -= ComboBox1_DropDownClosed;
Application.EndModal(this.comboBox1, DialogResult.OK);
}
private void ComboBox1_DropDownClosed(object sender, EventArgs e)
{
Application.EndModal(this.comboBox1, DialogResult.Cancel);
}
' Open the combo box drop down list and wait
' for the user to select an item or close the combo box.
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Me.ComboBox1.DroppedDown = True
AddHandler Me.ComboBox1.DropDownClosed, AddressOf ComboBox1_DropDownClosed
AddHandler Me.ComboBox1.SelectedIndexChanged, AddressOf ComboBox1_SelectedIndexChanged
' wait for the user to either pick an item or close the drop down.
Dim result As DialogResult = Application.DoModal(Me.ComboBox1)
' code execution will resume here.
End Sub
Private Sub ComboBox1_SelectedIndexChanged(sender As Object, e As EventArgs)
RemoveHandler Me.ComboBox1.DropDownClosed, AddressOf ComboBox1_DropDownClosed
Application.EndModal(Me.ComboBox1, DialogResult.OK)
End Sub
Private Sub ComboBox1_DropDownClosed(sender As Object, e As EventArgs)
Application.EndModal(Me.ComboBox1, DialogResult.Cancel)
End Sub
The code above opens a dropdown and waits for user action. DoModal returns DialogResult.Cancel if closed without selection, or DialogResult.OK otherwise.
This provides powerful control over code execution and user action synchronization.
Application.DoModalAsync(component) will be added in a future build.
