Contextual Menus

Introduction

1. Start Microsoft Visual Basic
2. Create a new Windows Application named AltairRealtors3b
3. In the Solution Explorer, right-click Form1.vb and click Rename
4. Type AltairRealtors.vb and press Enter
5. From the Menus & Toolbars section of the Toolbox, click the MenuStrip button and click the form
6. While the menu strip is still selected, in the Properties window, click (Name), type MenuMain  and press Enter
7. On the form, click Type Here, type File and press Enter
8. On the form, click File.
   In the Properties window, click (Name) and type MenuFile
9. On the form, click File and under it, click the Type Here box
10. Type New Property and press Enter
11. On the form, click File and click New Property.
    In the Properties window, click (Name) and type MenuFileNewProperty
12. On the form, click File and, under New Property, click the Type Here box
13. Type Exit and press Enter
14. On the form, click File and click Exit.
    In the Properties window, click (Name) and type MenuFileExit
15. Complete the design of the form as follows:
     

    Control Text Name Other Properties MenuStrip       Label Altair Realtors - Properties Listing   Font: Times New Roman, 21.75pt, style=Bold ForeColor: MediumBlue ListView   lvwProperties   Columns (Name) Text TextAlign Width colPropertyNumber Prop #   50 colPropertyType Property Type   78 colAddress Address   130 colCity City   80 colState State   40 colZIPCode ZIP Code Center 58 colBedrooms Beds Right 40 colBathrooms Baths Right 40 colMarketValue Market Value Right 75

16. On the main menu, click Project -> Add Windows Form...
17. Set the Name to RealEstateProperty and click Add
18. Design the form as follows:
     

    Control Text Name Other Properties Label Property #:     TextBox   txtPropertyNumber Modifiers: Public Label Property Type:     ComboBox   cbxPropertyTypes Modifiers: Public Items: Unknown Single Family Townhouse Condominium Label Address:     TextBox   txtAddress Modifiers: Public Label City:     TextBox   txtCity Modifiers: Public Label State:     ComboBox   cbxStates Modifiers: Public Items: DC MD PA VA WV Label ZIP Code:     TextBox   txtZIPCode Modifiers: Public Label Bedrooms:     TextBox 0 txtBedrooms Modifiers: Public Label Bathrooms:     TextBox 1.0 txtBathrooms Modifiers: Public Label Market Value:     TextBox 0.00 txtMarketValue Modifiers: Public Button OK btnOK DialogResult: OK Button Cancel btnCancel DialogResult: Cancel
    Form
    FormBorderStyle:	FixedDialog
    Text:	Altair Realtors - Available Property
    StartPosition:	CenterScreen
    AcceptButton:	btnOK
    CancelButton:	btnCancel
    MaximizeBox:	False
    MinimizeBox:	False
    ShowInTaskBar:	False

19. Display the AltairRealtors form
20. Right-click the form and click View Code
21. In the Class Name combo box, select MenuFileNewProperty
22. In the Method Name combo box, select Click and implement the event as follows:
     

    Private Sub MenuFileNewProperty_Click(ByVal sender As Object, _ ByVal e As System.EventArgs) _ Handles MenuFileNewProperty.Click Dim rndNumber As Random Dim number1 As Integer Dim number2 As Integer Dim PropertyNumber As String Dim dlgProperty As RealEstateProperty rndNumber = New Random(DateTime.Now.Millisecond) number1 = rndNumber.Next(100, 999) number2 = rndNumber.Next(100, 999) PropertyNumber = number1 & number2 dlgProperty = New RealEstateProperty dlgProperty.txtPropertyNumber.Text = PropertyNumber dlgProperty.Text = "Altair Realtors - New Property" If dlgProperty.ShowDialog() = Windows.Forms.DialogResult.OK Then Dim strPropertyType As String = dlgProperty.cbxPropertyTypes.Text Dim strAddress As String = dlgProperty.txtAddress.Text Dim strCity As String = dlgProperty.txtCity.Text Dim strState As String = dlgProperty.cbxStates.Text Dim strZIPCde As String = dlgProperty.txtZIPCode.Text Dim strBedrooms As String = dlgProperty.txtBedrooms.Text Dim strBathrooms As String = dlgProperty.txtBathrooms.Text Dim strMarketValue As String = dlgProperty.txtMarketValue.Text Dim lviProperty As ListViewItem = _ New ListViewItem(dlgProperty.txtPropertyNumber.Text) lviProperty.SubItems.Add(strPropertyType) lviProperty.SubItems.Add(strAddress) lviProperty.SubItems.Add(strCity) lviProperty.SubItems.Add(strState) lviProperty.SubItems.Add(strZIPCde) lviProperty.SubItems.Add(strBedrooms) lviProperty.SubItems.Add(strBathrooms) lviProperty.SubItems.Add(strMarketValue) lvwProperties.Items.Add(lviProperty) End If End Sub

23. In the Class Name combo box, select MenuFileExit
24. In the Method Name combo box, select Click and implement the event as follows:
     

    Private Sub MenuFileExit_Click(ByVal sender As Object, _ ByVal e As System.EventArgs) _ Handles MenuFileExit.Click End End Sub

25. Execute the application
     
    
26. To close the form, click File -> Exit

To support the creation and management of contextual menus, the .NET Framework provides the ContextMenuStrip class. This class is derived from ToolStripDropDownMenu, which itself is based on the ToolStripDropDown class. The ToolStripDropDown class is derived from ToolStrip.

To visually create a contextual menu, in the Menus & Toolbars section of the Toolbox, click the ContextMenuStrip button and click the form. Once you have a ContextMenuStrip object, you can create its menu items. To do this, as mentioned for the MenuStrip, you can click the first Type Here line, type a string, press Enter, and continue creating the other menu items in the same way.

Unlike a main menu, a popup menu provides a single list of items. If you want different popup menus for your form, you have two options. You can create various popup menus or programmatically change your single popup menu in response to something or some action on your form.

To programmatically create a contextual menu, start by declaring a handle to ContextMenuStrip. Here is an example:

Imports System.Drawing
Imports System.Windows.Forms

Module Exercise

    Public Class Starter
        Inherits Form

        Private Contextual As ContextMenuStrip

        Dim components As System.ComponentModel.Container

        Public Sub New()
            InitializeComponent()
        End Sub

        Public Sub InitializeComponent()

            Contextual = New ContextMenuStrip

        End Sub

    End Class

    Function Main() As Integer

        Dim frmStart As Starter = New Starter

        Application.Run(frmStart)

        Return 0
    End Function

End Module

To assist you with each item of a contextual menu, ToolStrip, the ancestor to the ContextMenuStrip class, is equipped with a property named Items. This property is of type ToolStripItemCollection, which is a collection-based class. The ToolStripItemCollection class implements the IList, the ICollection, and the IEnumerable interfaces.

To create one or more menu items, you can use the various techniques we reviewed for the main menu. Here are examples:

Imports System.Drawing
Imports System.Windows.Forms

Module Exercise

    Public Class Starter
        Inherits Form

        Private MenuEditCut As ToolStripMenuItem
        Private Contextual As ContextMenuStrip

        Dim components As System.ComponentModel.Container

        Public Sub New()
            InitializeComponent()
        End Sub

        Public Sub InitializeComponent()

            Contextual = New ContextMenuStrip
            MenuEditCut = New ToolStripMenuItem("Cut")

            Dim MenuEdit() As ToolStripMenuItem = _
            { _
                New ToolStripMenuItem("Copy"), _
                New ToolStripMenuItem("Paste") _
            }

        End Sub

    End Class

    Function Main() As Integer

        Dim frmStart As Starter = New Starter

        Application.Run(frmStart)

        Return 0
    End Function

End Module

After creating a menu item, to add it to the contextual menu, you can call the ToolStripItemCollection.Add() method. To add an array of items, you can call the create ToolStripItemCollection.AddRange() method. Here are examples:

Public Sub InitializeComponent()

            Contextual = New ContextMenuStrip
            MenuEditCut = New ToolStripMenuItem("Cut")

            Dim MenuEdit() As ToolStripMenuItem = _
            { _
                New ToolStripMenuItem("Copy"), _
                New ToolStripMenuItem("Paste") _
            }

            Contextual.Items.Add(MenuEditCut)
            Contextual.Items.AddRange(MenuEdit)

End Sub

1. From the Menus & Toolbars section of the Toolbox, click ContextMenuStrip and click the form
2. While the context menu strip is still selected, in the Properties window click (Name) and type MenuWithProperties
3. Then click Items and click its ellipsis button
4. Under the Select Item And Add To List combo box, make sure MenuItem is selected and click Add
5. On the right side, click Text and type Edit
6. Click (Name) and type MenuEditProperty
7. On the left side, click Add and, on the right side, change the properties as follows:
   Text: Delete
   (Name): MenuDeleteProperty
8. On the left side, click Add and, on the right side, change the properties as follows:
   Text: Clear
   (Name): MenuClearProperties
    
   
9. Click OK
10. From the Menus & Toolbars section of the Toolbox, click ContextMenuStrip and click the form
11. While the context menu strip is still selected, in the Properties window click (Name) and type MenuNoProperty
12. On the form, under ContextMenuStrip, click Type Here
13. Type New Property and press Enter
14. On the form, under ContextMenuStrip, click New Property
15. In the Properties window, click (Name), type MenuNewProperty and press Enter

By default, a newly created contextual menu is attached neither to the form nor to any control on it. In order to display a context menu, you must assign its name to the control. To support this, Control, the ancestor to all visual controls of the .NET Framework, is equipped, and provides to its children, a property named ContextMenuStrip, which is of type ContextMenuStrip.

To visually assign a contextual menu to a control during design, click the control. In the Properties window, click the ContextMenuStrip field, then click the arrow of its combo box, and select the menu. If you had created more than one contextual menu, the combo box would show all of them and you can choose the one you want to use as default.

To programmatically specify the contextual menu of a control, assign a ContextMenuStrip object to its ContextMenuStrip property. Here is an example:

Public Sub InitializeComponent()

            Contextual = New ContextMenuStrip
            MenuEditCut = New ToolStripMenuItem("Cut")

            Dim MenuEdit() As ToolStripMenuItem = _
            { _
                New ToolStripMenuItem("Copy"), _
                New ToolStripMenuItem("Paste") _
            }

            Contextual.Items.Add(MenuEditCut)
            Contextual.Items.AddRange(MenuEdit)

            ContextMenuStrip = Contextual

End Sub

After assigning a ContextMenuStrip object to a control, when you right-click (actually when the user right-clicks) the control, the contextual menu would display. The above code would produce:

1. Right-click the form and click View Code
2. Just under the Public Class AltairRealtors line, declare a ListViewItem variable named itmSelected
    

   Public Class AltairRealtors Private itmSelected As ListViewItem . . . No Change

3. In the Class Name combo box, select (AltairRealtors Events)
4. In the Method Name combo box, select Load and implement the event as follows:
    

   Private Sub AltairRealtors_Load(ByVal sender As Object, _ ByVal e As System.EventArgs) _ Handles Me.Load itmSelected = New ListViewItem() lvwProperties.ContextMenuStrip = MenuNoProperty End Sub

5. In the Class Name combo box, select lvwProperties
6. In the Method Name combo box, select MouseDown and implement the event as follows:
    

   Private Sub lvwProperties_MouseDown(ByVal sender As Object, _ ByVal e As System.Windows.Forms.MouseEventArgs) _ Handles lvwProperties.MouseDown If e.Button = Windows.Forms.MouseButtons.Right Then If lvwProperties.SelectedItems.Count > 0 Then itmSelected = lvwProperties.SelectedItems(0) Else itmSelected = Nothing End If End If End Sub

7. Save the file

In your application, you can create as many contextual menus as you want. If you have different controls, each can have its own contextual menu or many can share a contextual menu. Also, you can use different contextual menus for a control and decide what menu to display when/why.

There is nothing particularly specific with writing code for a popup menu item. You approach it exactly as if you were dealing with a menu item of a main menu. You can write code for an item of a popup menu independent of any other item of a main menu. If you want an item of a popup menu to respond to the same request as an item of a main menu, you can write code for one of the menu items (either the item on the main menu or the item on the popup menu) and simply call its Click event in the event of the other menu item.

1. In the Class Name combo box, select lvwProperties
2. In the Method Name combo box, select ItemSelectionChanged and implement the event as follows:
    

   Private Sub lvwProperties_MouseDown(ByVal sender As Object, _ ByVal e As System.Windows.Forms.MouseEventArgs) _ Handles lvwProperties.MouseDown If e.Button = Windows.Forms.MouseButtons.Right Then If lvwProperties.SelectedItems.Count > 0 Then itmSelected = lvwProperties.SelectedItems(0) Else itmSelected = Nothing End If End If End Sub

3. In the Class Name combo box, select MenuEditProperties
4. In the Method Name combo box, select Click and implement the event as follows:
    

   Private Sub MenuEditProperty_Click(ByVal sender As Object, _ ByVal e As System.EventArgs) _ Handles MenuEditProperty.Click ' Prepare to open the AvailableProperties dialog box Dim dlgProperty As RealEstateProperty = New RealEstateProperty ' Make sure an item, and only one, is selected If (lvwProperties.SelectedItems.Count = 0) Or _ (lvwProperties.SelectedItems.Count > 1) Then Exit Sub End If ' Identify the item that is currently selected Dim lviCurrent As ListViewItem = lvwProperties.SelectedItems(0) ' Display the ItemDetails dialog box with the item number dlgProperty.txtPropertyNumber.Text = lviCurrent.Text dlgProperty.cbxPropertyTypes.Text = lviCurrent.SubItems(1).Text dlgProperty.txtAddress.Text = lviCurrent.SubItems(2).Text dlgProperty.txtCity.Text = lviCurrent.SubItems(3).Text dlgProperty.cbxStates.Text = lviCurrent.SubItems(4).Text dlgProperty.txtZIPCode.Text = lviCurrent.SubItems(5).Text dlgProperty.txtBedrooms.Text = lviCurrent.SubItems(6).Text dlgProperty.txtBathrooms.Text = lviCurrent.SubItems(7).Text dlgProperty.txtMarketValue.Text = lviCurrent.SubItems(8).Text If dlgProperty.ShowDialog() = Windows.Forms.DialogResult.OK Then lvwProperties.SelectedItems(0).Text = _ dlgProperty.txtPropertyNumber.Text lvwProperties.SelectedItems(0).SubItems(1).Text = _ dlgProperty.cbxPropertyTypes.Text lvwProperties.SelectedItems(0).SubItems(2).Text = _ dlgProperty.txtAddress.Text lvwProperties.SelectedItems(0).SubItems(3).Text = _ dlgProperty.txtCity.Text lvwProperties.SelectedItems(0).SubItems(4).Text = _ dlgProperty.cbxStates.Text lvwProperties.SelectedItems(0).SubItems(5).Text = _ dlgProperty.txtZIPCode.Text lvwProperties.SelectedItems(0).SubItems(6).Text = _ dlgProperty.txtBedrooms.Text lvwProperties.SelectedItems(0).SubItems(7).Text = _ dlgProperty.txtBathrooms.Text lvwProperties.SelectedItems(0).SubItems(8).Text = _ dlgProperty.txtMarketValue.Text End If End Sub

5. In the Class Name combo box, select MenuDeleteProperty
6. In the Method Name combo box, select Click and implement the event as follows:
    

   Private Sub MenuDeleteProperty_Click(ByVal sender As Object, _ ByVal e As System.EventArgs) _ Handles MenuDeleteProperty.Click If lvwProperties.SelectedItems.Count = 0 Then Exit Sub Dim Answer As MsgBoxResult Answer = MsgBox("Are you sure you want " & _ "to delete that property?", _ MsgBoxStyle.YesNo Or MsgBoxStyle.Question, _ "Delete Property") If Answer = MsgBoxResult.Yes Then lvwProperties.SelectedItems(0).Remove() End If End Sub

7. In the Class Name combo box, select MenuClearProperty
8. In the Method Name combo box, select Click and implement the event as follows:
    

   Private Sub MenuClearProperties_Click(ByVal sender As Object, _ ByVal e As System.EventArgs) _ Handles MenuClearProperties.Click Dim Answer As MsgBoxResult Answer = MsgBox("Are you sure you want " & _ "to delete all properties?", _ MsgBoxStyle.YesNo Or MsgBoxStyle.Question, _ "Remove all Properties") If Answer = MsgBoxResult.Yes Then lvwProperties.Items.Clear() End If End Sub

9. In the Class Name combo box, select MenuNewProperty
10. In the Method Name combo box, select Click and implement the event as follows:
     

    Private Sub MenuNewProperty_Click(ByVal sender As Object, _ ByVal e As System.EventArgs) _ Handles MenuNewProperty.Click MenuFileNewProperty_Click(sender, e) End Sub

11. Execute the application and test it
12. Right-click an empty line of the list view to see the contextual menu and click New Property
     
    
     
    
13. Right-click the list view and click Edit
     
    
     
    
14. Right-click a row on the form and click Delete
15. Accept to delete the property
16. Close the form and return to your programming environment