Start Microsoft Office Outlook 2007.

On the Tools menu, point to Forms, and then click Design a Form.

In the Design Form box, click Task, and then click Open.

On the Developer tab, in the Design group, click Form Region and then New Form Region.

A new form region opens. If the Field Chooser does not appear, click Field Chooser in the Tools group.

Drag the Subject field and the % Complete field from the Field Chooser to the form region.

In the Tools group, click Control Toolbox to open the Toolbox.

Drag a Label from the Toolbox to the form region. Position the label beneath the Subject and % Complete fields.

Right-click the label, and then click Advanced Properties.

In the Properties window, set the Caption property to This task depends on the following tasks, set the Width property to 200, and then click Apply.

Drag a ListBox control from the Toolbox to the form region. Position the list box beneath the This task depends on the following tasks label.

Select the list box that you just added.

In the Properties window, set Width to 300, and then click Apply.

Drag a Label from the Toolbox to the form region. Position the label beneath the list box.

Select the label that you just added.

In the Properties window, set the Caption property to Select a task to add to the list of dependent tasks, set the Width property to 200, and then click Apply.

Drag a ComboBox control from the Toolbox to the form region. Position the combo box beneath the Select a task to add to the list of dependent tasks label.

Select the combo box that you just added.

In the Properties window, set the Width property to 300, and then click Apply.

Drag a CommandButton control from the Toolbox to the form region. Position the command button next to the combo box.

Select the command button that you just added.

In the Properties window, set Name to AddDependentTask, set Caption to Add Dependent Task, set Width to 100, and then click Apply.

In the Field Chooser, click New.

In the New Field dialog box, type hiddenField in the Name field, and then click OK.

Drag the hiddenField field from the Field Chooser to the form region.

In the Properties window, set Visible to 0 - False, and then click Apply.

On the Developer tab, in the Design group, click Form Region, and then click Save Form Region As. Name the form region TaskFormRegion and save it to a local directory on your computer.

Outlook saves the form region as an Outlook Form Storage (.ofs) file. The form region is saved with the name TaskFormRegion.ofs.

Exit Outlook.

In Visual Studio, create an Outlook 2007 add-in project with the name TaskAddIn.

In the New Project dialog box, select Create directory for solution.

Save the project to the default project directory.

For more information, see How to: Create Visual Studio Tools for Office Projects.

In Solution Explorer, right-click the TaskAddIn project, point to Add, and then click New Item.

In the Templates pane, select Outlook Form Region, name the file TaskFormRegion, and then click Add.

The New Outlook Form Region wizard starts.

On the Select how you want to create the form region page, click Import an Outlook Form Storage (.ofs) File, and then click Browse.

In the Existing Outlook Form Region File Location dialog box, browse to the location of TaskFormRegion.ofs, select TaskFormRegion.ofs, click Open, and then click Next.

On the Select the type of form region you want to create page, click Replace-all, and then click Next.

A replace-all form region replaces the entire Outlook form. For more information about form region types, see Creating Outlook Form Regions.

On the Supply descriptive text and select your display preferences page, click Next.

On the Identify the message classes that will display this form region page, in the Which custom message classes will display this form region field, type IPM.Task.TaskFormRegion, and then click Finish.

A TaskFormRegion.cs or TaskFormRegion.vb file is added to your project.

In Solution Explorer, right-click TaskFormRegion.cs or TaskFormRegion.vb, and then click View Code.

TaskFormRegion.cs or TaskFormRegion.vb opens in the Code Editor.

Add the following code to the TaskFormRegion class. This code populates the combo box on the form region with the subject line of each task from the Outlook Tasks folder.

Private Sub populateComboBox()
    Dim Application As New Outlook.Application()
    Dim outlookNameSpace As Outlook.NameSpace = _
    Application.GetNamespace("MAPI")
    Dim taskFolder As Outlook.MAPIFolder = _
    outlookNameSpace.GetDefaultFolder _
        (Microsoft.Office.Interop.Outlook.OlDefaultFolders.olFolderTasks)
    Dim taskItems As Outlook.Items = taskFolder.Items
    Dim task As Outlook.TaskItem
    For Each task In taskItems
        If Not (task.Subject Is Nothing) Then
            comboBox1.AddItem(task.Subject, System.Type.Missing)
        End If
    Next task
    comboBox1.Text = comboBox1.GetItem(0)
End Sub

private void populateComboBox()
{
    Outlook.Application Application = new Outlook.Application();
    Outlook.NameSpace outlookNameSpace = Application.GetNamespace("MAPI");
    Outlook.MAPIFolder taskFolder = outlookNameSpace.GetDefaultFolder(
        Microsoft.Office.Interop.Outlook.OlDefaultFolders.olFolderTasks);
    Outlook.Items taskItems = taskFolder.Items;
    foreach (Outlook.TaskItem task in taskItems)
    {
        if (task.Subject != null)
        {
            comboBox1.AddItem(task.Subject, System.Type.Missing);
        }
    }
    comboBox1.Text = comboBox1.GetItem(0);
}

Add the following code to the TaskFormRegion class. This code performs the following tasks:

• Locates the Microsoft.Office.Interop.Outlook.TaskItem in the Tasks folder by calling the FindTaskBySubjectName helper method and passing the subject of the desired task. You will add the FindTaskBySubjectName helper method in the next step.

• Adds the Microsoft.Office.Interop.Outlook.TaskItem.Subject and Microsoft.Office.Interop.Outlook.TaskItem.PercentComplete values to the dependent task list box.

• Adds the subject of the task to the hidden field on the form region. The hidden field stores these values as part of the Outlook item.

Private Sub AddDependentTask_Click1() Handles addDependentTask.Click
    Dim tempTaskItem As Outlook.TaskItem = FindTaskBySubjectName _
        (comboBox1.Text)
    If Not (tempTaskItem Is Nothing) Then
        Me.listBox1.AddItem(tempTaskItem.PercentComplete.ToString() & _
            "% Complete -- " & tempTaskItem.Subject, System.Type.Missing)
        Me.olkTextBox3.Text = Me.olkTextBox3.Text & "|" & tempTaskItem.Subject
    End If
End Sub

    void AddDependentTask_Click()
    {
        Outlook.TaskItem tempTaskItem = FindTaskBySubjectName(comboBox1.Text);
        if (tempTaskItem != null)
        {
            this.listBox1.AddItem(tempTaskItem.PercentComplete.ToString()
+ "% Complete -- " + tempTaskItem.Subject, System.Type.Missing);
            this.olkTextBox3.Text = this.olkTextBox3.Text + "|" + 
                tempTaskItem.Subject;
        }
    }

Add the following code to the TaskFormRegion class. This code provides the helper method FindTaskBySubjectName that was described in the preceding step.

Private Function FindTaskBySubjectName(ByVal subjectName As String) _
    As Outlook.TaskItem
    Dim Application As New Outlook.Application()
    Dim outlookNameSpace As Outlook.NameSpace = _
        Application.GetNamespace("MAPI")
    Dim tasksFolder As Outlook.MAPIFolder = _
        outlookNameSpace.GetDefaultFolder _
            (Microsoft.Office.Interop.Outlook.OlDefaultFolders.olFolderTasks)
    Dim taskItems As Outlook.Items = tasksFolder.Items
    Dim taskItem As Outlook.TaskItem
    For Each taskItem In taskItems
        If taskItem.Subject = subjectName Then
            Return taskItem
        End If
    Next taskItem
    Return Nothing
End Function

private Outlook.TaskItem FindTaskBySubjectName(string subjectName)
{
    Outlook.Application Application = new Outlook.Application();
    Outlook.NameSpace outlookNameSpace = Application.GetNamespace("MAPI");
    Outlook.MAPIFolder tasksFolder =
        outlookNameSpace.GetDefaultFolder(
    Microsoft.Office.Interop.Outlook.
        OlDefaultFolders.olFolderTasks);
    Outlook.Items taskItems = tasksFolder.Items;
    foreach (Outlook.TaskItem taskItem in taskItems)
    {
        if (taskItem.Subject == subjectName)
        {
            return taskItem;
        }
    }
    return null;
}

Add the following code to the TaskFormRegion class. This code performs the following tasks:

• Refreshes the list box on the form region with the current completion status of each dependent task.

• Parses the hidden text field to obtain the subject of each dependent task. It then locates each Microsoft.Office.Interop.Outlook.TaskItem in the Tasks folder by calling the FindTaskBySubjectName helper method and passing the subject of each task.

• Adds the Microsoft.Office.Interop.Outlook.TaskItem.Subject and Microsoft.Office.Interop.Outlook.TaskItem.PercentComplete values to the dependent task list box.

Private Sub RefreshTaskListBox()
    listBox1.Clear()
    Dim tempTaskItem As Outlook.TaskItem
    Dim tempArray As [String]() = olkTextBox3.Text.Split(New [Char]() {"|"c})

    Dim tempString As String
    For Each tempString In tempArray
        tempTaskItem = FindTaskBySubjectName(tempString)
        If Not (tempTaskItem Is Nothing) Then
            Me.listBox1.AddItem(tempTaskItem.PercentComplete.ToString() & _
                "% Complete -- " & tempTaskItem.Subject, System.Type.Missing)
        End If
    Next tempString
End Sub

void RefreshTaskListBox()
{
    listBox1.Clear();
    Outlook.TaskItem tempTaskItem;
    String[] tempArray = olkTextBox3.Text.Split(new Char[] { '|' });

    foreach (string tempString in tempArray)
    {
        tempTaskItem = FindTaskBySubjectName(tempString);
        if (tempTaskItem != null)
        {
            this.listBox1.AddItem(tempTaskItem.PercentComplete.ToString()
                + "% Complete -- " + tempTaskItem.Subject, 
                    System.Type.Missing);
        }
    }
}

Replace the TaskFormRegion_FormRegionShowing event handler with the following code. This code performs the following tasks:

• Populates the combo box on the form region with task subjects when the form region appears.

• Calls the RefreshTaskListBox helper method when the form region appears. This displays any dependent tasks that were added to the list box when the item was previously opened.

Private Sub TaskFormRegion_FormRegionShowing(ByVal sender As Object, _
    ByVal e As System.EventArgs) Handles MyBase.FormRegionShowing
    populateComboBox()
    RefreshTaskListBox()
End Sub

private void TaskFormRegion_FormRegionShowing
    (object sender, EventArgs e)
{
    populateComboBox();
    RefreshTaskListBox();
    this.addDependentTask.Click += new
    Microsoft.Office.Interop.Outlook.
        OlkCommandButtonEvents_ClickEventHandler(AddDependentTask_Click);

}

Press F5 to run the project.

Outlook starts.

In Outlook, on the File menu, point to New, and then click Task.

In the task form, type Dependent Task in the Subject field.

On the Task tab of the Ribbon, in the Actions group, click Save & Close.

In Outlook, on the File menu, point to New, and then click Choose Form.

In the Choose Form dialog box, click TaskFormRegion, and then click Open.

The TaskFormRegion form region appears. This form replaces the entire task form. The Select a task to add to the list of dependent tasks combo box is populated with other tasks in the Tasks folder.

On the task form, in the Subject field, type Primary Task.

In the Select a task to add to the list of dependent tasks combo box, select Dependent Task, and then click Add Dependent Task.

0% Complete -- Dependent Task appears in the This task depends on the following tasks list box. This demonstrates that you successfully handled the Microsoft.Office.Interop.Outlook.OlkCommandButton.Click event of the button.

Save and close the Primary Task item.

Reopen the Dependent Task item in Outlook.

On the Dependent Task form, change the % Complete field to 50%.

On the Task tab of the Dependent Task Ribbon, in the Actions group, click Save & Close.

Reopen the Primary Task item in Outlook.

50% Complete -- Dependent Task now appears in the This task depends on the following tasks list box.