Ribbon Invalidate does not work - outlook

Question

I have a simple outlook ribbon with an editBox. Once the user clicks the send button, I capture the string in the editBox and use it in the Application_ItemSend..
My problem is, after the function is done, I want to RESET the UI of the ribbon (just the editBox) so that the user won't have the previously typed string in the same box when opening up a new message screen. I tried the Ribbon.Invalidate but I can't seem to get rid of that string value. When I re-open the "New Email" screen, the old value is still there.
Here is the code:
<customUI xmlns="http://schemas.microsoft.com/office/2009/07/customui" onLoad="Ribbon_Load_2010">
<ribbon>
<tabs>
<tab idMso="TabNewMailMessage">
<group id="TaskManager" insertBeforeMso="GroupSend" label="Task Manager">
<editBox id="editboxTaskID" label="Task ID #: " onChange="editboxTaskID_OnChange"
imageMso="RecordsAddFromOutlook" sizeString="wwwwww"/>
</group>
</tab>
</tabs>
</ribbon>
</customUI>
And the VB Code:
<Runtime.InteropServices.ComVisible(True)> _
Public Class CustomRibbon
Implements Office.IRibbonExtensibility
Private ribbon As Office.IRibbonUI
Public strTask_ID As String = ""
Public Sub New()
End Sub
Public Function GetCustomUI(ByVal ribbonID As String) As String Implements Office.IRibbonExtensibility.GetCustomUI
Return GetResourceText("Addin.Ribbon.xml")
End Function
Private Sub Application_ItemSend(ByVal Item As Object, ByRef Cancel As Boolean)
Me.ribbon.Invalidate()
Try
'SOME CODE HERE WHICH WORKS FINE!
Catch ex As Exception
End Try
End Sub
'Create callback methods here. For more information about adding callback methods, select the Ribbon XML item in Solution Explorer and then press F1.
Public Sub Ribbon_Load_2010(ByVal ribbonUI As Office.IRibbonUI)
Me.ribbon = ribbonUI
AddHandler Globals.ThisAddIn.Application.ItemSend, AddressOf Application_ItemSend
End Sub
Public Sub editboxTaskID_OnChange(ByVal control As Office.IRibbonControl, ByVal Text As String)
strTask_ID = Text
End Sub
Public Sub AttachmentRibonClick(ByVal control As Microsoft.Office.Core.IRibbonControl)
Globals.ThisAddIn.TriggerTaskWindow("Attachment")
End Sub
Private Shared Function GetResourceText(ByVal resourceName As String) As String
Dim asm As Reflection.Assembly = Reflection.Assembly.GetExecutingAssembly()
Dim resourceNames() As String = asm.GetManifestResourceNames()
For i As Integer = 0 To resourceNames.Length - 1
If String.Compare(resourceName, resourceNames(i), StringComparison.OrdinalIgnoreCase) = 0 Then
Using resourceReader As IO.StreamReader = New IO.StreamReader(asm.GetManifestResourceStream(resourceNames(i)))
If resourceReader IsNot Nothing Then
Return resourceReader.ReadToEnd()
End If
End Using
End If
Next
Return Nothing
End Function
End Class

Answer 1

The invalidate method is used to signal that a control has been updated and needs to be re-rendered on the screen. It will not clear data from a control. What you need to do is set the property on the control (the edit box in this case) that stores the offending string value to an empty string.

Answer 2

Ok, I figured it out.
Apparently after you invalidate the controls, you need to use GetText function of the Editbox to init the value.
Public Function editboxTaskID_GetText(ByVal control As Office.IRibbonControl) As String
Return ""
End Function
I also noticed other sites use different signature for the function - which does not work. I believe Microsoft changed this from a Sub to a Function when moving to 2010 Interop.
I wish Microsoft had better documentation for this.
Happy programming!