Posts in Category: vsto

Troubleshooting Outlook Form Regions

Recently I had to debug a strange issue with an Outlook VSTO plugin where the plugin would install smoothly and load correctly but my custom calendar region was not showing as expected.  To complicate matters a little further, I had some clients on 32-bit and some on 64-bit desktop systems so it was not a straightforward install.

You can find the base steps for registering a VSTO add-in here.

Note: An easy check to see if your add-in is automatically loading correctly is to verify that the LoadBehavior key stays at 3.  You can keep the registry open while you load your Office application and refresh to see if it was unloaded.

Outlook Form Regions have an extra step though and depending on the desktop architecture you are on, you’ll need to

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VSTO – Enabling Ribbon Controls at RunTime

I recently ran into an issue where I needed to enable and disable Ribbon controls in a VSTO plugin where the Ribbon controls were initialized through a Ribbon.xml file.

This can be a bit challenging s the controls in the Ribbon XML file are not available to your code at design time when you are trying to write the actual code.

In addition, I needed to trigger the decision handling logic from another section of code not associated to the Ribbon.

Accomplishing this task involved a number of steps and was done building an integration to Outlook (not sure if this would be similar in Word or Excel).

Identify the controls at run-time

In each control that I wanted to control the state on, at the time of the Ribbon’s instantiation I had them call

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Retrieving Email Addresses in Outlook

Sometimes it seems that what we thought was the easiest problem to solve actually turns out taking the longest amount of time to figure out.

Case in point – finding the email address of the currently logged in user running Outlook in a VSTO plugin.

If you are looking to do this, see below and let the code set you free.

Recipient CurrentUser = this.Application.Session.CurrentUser;


A little longer and less direct than I would have thought (i.e., at this stage, my user is not a recipient to anything) but the reasoning becomes a little more apparent if I am trying to find the email addresses on a set of recipients on either an appointment or mail message.


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Creating a custom Tab in VSTO

If you haven’t used VSTO, it’s the framework for developing Office Integrations.  Yes, people are still developing Office plugins, although Flow is coming on strong, there is still a need for organizations to have components directly embedded in their primary applications of choice.

If you’re looking to get started on building your own Tab in Office you can do this very easily by adding a Ribbon.xml file to your VSTO project with the following syntax.

<?xml version="1.0" encoding="UTF-8"?>
<customUI xmlns="" onLoad="Ribbon_Load">
 <!--<tab idMso="TabMail">-->
 <tab id="tabForgotten" label="Coder">
 <group id="MyGroup" label="Content">
 <button id="btnGo" label="Connect" 
 screentip="Go" onAction="OnConnectClicked"
 supertip="Go to start."/>

Once you’ve added that snippet, simply navigate back to your main AddIn.cs file and instantiate your ribbon.

protected override Microsoft.Office.Core.IRibbonExtensibility CreateRibbonExtensibilityObject()
return new SuperRibbon();

Compile and run (in this example, I created an Outlook VSTO plugin) and you

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