Creating a DropDownButton / SplitButton which shows the selected item’s text

Product Version	Product	Author	Last modified
Q2 2007	RadControls for WinForms	Angel Kanchev	August 13, 2007

HOW-TO
Create a DropDownButton / SplitButton which shows the selected item’s text

DESCRIPTION
This KB article describes a way to show a DropDownButton item’s text in the button itself, after the item has been clicked. It also applies to the SplitButton control.

SOLUTION

1. Subscribe to the Click event for all menu items in the DropDownButton that have no subitems.
2. Subscribe for Load and FormClose events of the Form and fill them like this:
   

private void Form1_Load(object sender, EventArgs e)        
{        
    RadDropDownButtonElement buttonElement = (RadDropDownButtonElement)this.radDropDownButton1.RootElement.Children[0];        
    SubscribeMenuItems(buttonElement.DropDownMenu.Items);        
}        

private void Form1_FormClosed(object sender, FormClosedEventArgs e)        
{        
    RadDropDownButtonElement buttonElement = (RadDropDownButtonElement)this.radDropDownButton1.RootElement.Children[0];        
    UnsubscribeMenuItems(buttonElement.DropDownMenu.Items);        
}    

Class SurroundingClass
    Private Sub Form1_Load(ByVal sender As Object, ByVal e As EventArgs)
        Dim buttonElement As RadDropDownButtonElement = CType(Me.radDropDownButton1.RootElement.Children(0), RadDropDownButtonElement)
        SubscribeMenuItems(buttonElement.DropDownMenu.Items)
    End Sub

    Private Sub Form1_FormClosed(ByVal sender As Object, ByVal e As FormClosedEventArgs)
        Dim buttonElement As RadDropDownButtonElement = CType(Me.radDropDownButton1.RootElement.Children(0), RadDropDownButtonElement)
        UnsubscribeMenuItems(buttonElement.DropDownMenu.Items)
    End Sub
End Class

1. Add the private methods that will recursively subscribe / unsubscribe for Click event for every menu item that has no subitems:
   

private void SubscribeMenuItems(RadItemCollection menuItems)        
{        
    for (int i = 0; i < menuItems.Count; i++)        
    {        
        RadMenuItem subMenuItem = menuItems[i] as RadMenuItem;        
        if (subMenuItem != null)        
        {        
            if (subMenuItem.Items.Count == 0)        
                subMenuItem.Click += new EventHandler(DropDownMenuItem_Click);        
            else        
                SubscribeMenuItems(subMenuItem.Items);        
        }        
    }        
}        

private void UnsubscribeMenuItems(RadItemCollection menuItems)        
{        
    for (int i = 0; i < menuItems.Count; i++)        
    {        
        RadMenuItem subMenuItem = menuItems[i] as RadMenuItem;        
        if (subMenuItem != null)        
        {        
            if (subMenuItem.Items.Count == 0)        
                subMenuItem.Click -= new EventHandler(DropDownMenuItem_Click);        
            else        
                UnsubscribeMenuItems(subMenuItem.Items);        
        }        
    }        
}        

private void DropDownMenuItem_Click(object sender, EventArgs e)        
{        
    RadMenuItem clickedMenuItem = (RadMenuItem)sender;        
    this.radDropDownButton1.Text = clickedMenuItem.Text;        
}  

Class SurroundingClass
    Private Sub SubscribeMenuItems(ByVal menuItems As RadItemCollection)
        For i As Integer = 0 To menuItems.Count - 1
            Dim subMenuItem As RadMenuItem = TryCast(menuItems(i), RadMenuItem)

            If subMenuItem IsNot Nothing Then

                If subMenuItem.Items.Count = 0 Then
                    subMenuItem.Click += New EventHandler(AddressOf DropDownMenuItem_Click)
                Else
                    SubscribeMenuItems(subMenuItem.Items)
                End If
            End If
        Next
    End Sub

    Private Sub UnsubscribeMenuItems(ByVal menuItems As RadItemCollection)
        For i As Integer = 0 To menuItems.Count - 1
            Dim subMenuItem As RadMenuItem = TryCast(menuItems(i), RadMenuItem)

            If subMenuItem IsNot Nothing Then

                If subMenuItem.Items.Count = 0 Then
                    subMenuItem.Click -= New EventHandler(AddressOf DropDownMenuItem_Click)
                Else
                    UnsubscribeMenuItems(subMenuItem.Items)
                End If
            End If
        Next
    End Sub

    Private Sub DropDownMenuItem_Click(ByVal sender As Object, ByVal e As EventArgs)
        Dim clickedMenuItem As RadMenuItem = CType(sender, RadMenuItem)
        Me.radDropDownButton1.Text = clickedMenuItem.Text
    End Sub
End Class

The event handler DropDownMenuItem_Click() does the job here -  the text of the DropDown button is set to the text of the clicked menu item.

Note that the subscription for Click must be synchronized with the menu items. If a menu item is added DropDownMenuItem_Click() must be added to its Click event. If a menu item is removed its Click event must be unsubscribed. For simplicity (and when the menu items are not too many) before modification of the menu items can be called UnsubscribeMenuItems() and after the modification - SubscribeMenuItems().