title: Making an add-in ribbon button do something
body: <p>I have been following the tutorial for adding the add-ins ribbon to Outlook.  In my project I have MyRibbon.vb and MyRibbon.xml.  I have edited MyRibbon.xml so there is a button that says "Green Print".</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;customUI xmlns="http://schemas.microsoft.com/office/2009/07/customui" onLoad="Ribbon_Load"&gt;
    &lt;ribbon&gt;
      &lt;tabs&gt;
        &lt;tab idMso="TabAddIns"&gt;
          &lt;group id="MyGroup"
                 label="My Group"&gt;
            &lt;button id="printButton" label="Green Print" /&gt;
          &lt;/group&gt;
        &lt;/tab&gt;
      &lt;/tabs&gt;
    &lt;/ribbon&gt;
  &lt;/customUI&gt;
  </code></pre>
  
  <p>In MyRibbon.vb I have added some code which I was hoping would display a message saying "Hello World" when the button is clicked:</p>
  
  <pre><code>#Region "Ribbon Callbacks"
      'Create callback methods here. For more information about adding callback methods, visit https://go.microsoft.com/fwlink/?LinkID=271226
      Public Sub Ribbon_Load(ByVal ribbonUI As Office.IRibbonUI)
          Me.ribbon = ribbonUI
      End Sub
  
      Public Sub OnActionCallback(ByVal control As Office.IRibbonControl,
          ByVal isPressed As Boolean)
  
          If (control.Id = "printButton") Then
              MsgBox("Hello World!")
          End If
  
      End Sub
  
  #End Region
  </code></pre>
  
  <p>However when I click on the Green Print button in the add-ins ribbon nothing happens - no error message or anything just nothing.  Where am I going wrong please?</p>