test.cs

// create a new RibbonItem
RibbonButton rbMyButton = new RibbonButton()
{
Text = "My RibbonButton",
LargeIcon = Image.FromFile("icons/clipboard.png"),
SmallIcon = Image.FromFile("icons/checkmark.png")
};

// attach Click event
rbMyButton.Click += RbMyButton_Click;

// create a new RibbonGroup
HorizontalRibbonGroup rgMyRibbonGroup = new HorizontalRibbonGroup()
{
Text = "My RibbonGroup",
ShowSeperator = false,
SmallIcon = Image.FromFile("icons/checkmark.png"),
LargeIcon = Image.FromFile("icons/clipboard.png"),
};

// add the RibbonItem to the RibbonGroup
rgMyRibbonGroup.RibbonItems.Add(rbMyButton);