Outlook VSTO AddIn /自定义功能区:如何在Outlook 2016中将自定义功能区添加到主组(主窗口)

<customUI xmlns="http://schemas.microsoft.com/office/2009/07/customui">
  <ribbon>
    <tabs>
      <tab id="customTab" label="My Custom Tab">
        <group id="customGroup" label="Custom Group">
          <button id="customButton" label="Click Me" onAction="OnButtonClick"/>
        </group>
      </tab>
    </tabs>
  </ribbon>
</customUI>

using System;
using System.Windows.Forms;
using Microsoft.Office.Tools.Ribbon;

namespace OutlookAddIn
{
    public partial class ThisAddIn
    {
        private Ribbon ribbon;

        protected override Microsoft.Office.Core.IRibbonExtensibility CreateRibbonExtensibilityObject()
        {
            return new CustomRibbon();
        }

        private void OnButtonClick(Office.IRibbonControl control)
        {
            MessageBox.Show("Button Clicked!");
        }
    }

    public class CustomRibbon : Office.IRibbonExtensibility
    {
        private Office.IRibbonUI ribbon;

        public string GetCustomUI(string ribbonID)
        {
            return Properties.Resources.CustomRibbon;
        }

        public void Ribbon_Load(Office.IRibbonUI ribbonUI)
        {
            this.ribbon = ribbonUI;
        }
    }
}