VSTO for MS Outlook can be a powerful way to customize Outlook programmatically. However, the syntax can be finicky at times and I have found a few instances where the programming logic becomes tricky.
For example, you can use VSTO to add a text box to the Outlook command bar window. This can be put to a number of good uses when building a custom component for Outlook. My thoughts behind adding the controls to Outlook were to allow the user to select a type of search to run in the custom dropdown list, and then to use the text box for the user to add text that the system would use to run a search on custom email fields.
In my case I wanted to add a textbox and a ComboBox to my main Outlook Explorer view. The VSTO controls in Outlook are called msoControlEdit and msoControlComboBox respectively.
At first glance adding a simple text box and dropdown list sounds like a simple requirement. But as I found out, this isn’t quite the case. The problem? Outlook by default will clear any entered text from the new text box when focus is lost. I’m not sure what the reasoning behind this is, but from reading help articles and forum posts, it appears that many people are coming up against the same problem.
As a positive, the ComboBox control does retain selected text, so we will not need to worry about handling this control.
For the convenience of readers of this article; I am including a full example of how to add a textbox and a ComboBox to the Outlook main command bar at the end of this article.
How can one get Outlook to keep text from a textbox when the focus is lost?
The answer lies in adding a timer control from the Windows.Forms library. The timer needs to tick at a reasonable rate and then store newly entered text into a member variable in the ThisAddIn class. I did spend some time checking if this was the only solution, and in fact it is.
In the example code below I have set the timer to tick at once per second. This is frequent enough to catch text changes while not consuming too many clock cycles so that the application performance is still smooth.
Imports Outlook = Microsoft.Office.Interop.Outlook Imports Office = Microsoft.Office.Core Imports System.Windows.Forms Public Class ThisAddIn Dim WithEvents edt As Office.CommandBarComboBox Dim WithEvents editor As Office.CommandBarComboBox Dim WithEvents timer As New Timer() Dim strSearchText As String = Nothing Private Sub ThisAddIn_Startup() Handles Me.Startup Dim cbStandard As Office.CommandBar = Nothing cbStandard = Application.ActiveExplorer().CommandBars("Standard") timer.Interval = 1000 timer.Enabled = True editor = CType(cbStandard.FindControl(Tag:="Search Box", Visible:=True, Recursive:=False), Office.CommandBarControl) If editor Is Nothing Then editor = cbStandard.Controls.Add(Type:=Office.MsoControlType.msoControlEdit, Temporary:=True) editor.Tag = "Search Box" editor.Caption = "Use this text area to search for Information in your folder." End If edt = CType(cbStandard.FindControl(Tag:="DDL", Visible:=True, Recursive:=False), Office.CommandBarControl) If (edt Is Nothing) Then edt = cbStandard.Controls.Add(Type:=Office.MsoControlType.msoControlComboBox, Temporary:=True) edt.Caption = "Use this search area to specify the search to run for emails in your folder." edt.Tag = "Search Text" edt.Parameter = "tbParameter" edt.Visible = True edt.Width = 150 edt.TooltipText = "Use this search area to specify the TYPE of search to run for emails in your folder." edt.AddItem("Clear Search") edt.AddItem("QuickSearch Selected Folder") edt.AddItem("Create Report for") edt.Text = "Clear Search" edt.DropDownWidth = 250 End If End Sub Private Sub timer_Tick(sender As Object, e As System.EventArgs) Handles timer.Tick Try Dim strEnteredText As String = (editor.Text).Trim() Dim strSelectedSearchText As String = (edt.Text).Trim() If (strEnteredText).Length > 0 Then If ("Clear Search").Equals(strSelectedSearchText) Then editor.Text = "" strSearchText = "" Else strSearchText = strEnteredText If Not (editor.Text).Equals(strSearchText) Then editor.Text = strSearchText End If Else editor.Text = strSearchText End If editor.Visible = True Catch ex As Exception End Try End Sub Private Sub ThisAddIn_Shutdown() Handles Me.Shutdown End Sub End Class
- Here is a link to a useful article I found about using a ticker control to retain msoControlEdit text values on the MSDN discussion forums