3rdpartylibs/fastreports.wpf/FastReport.Forms.WPF/CustomControls/ToolStripSplitButton.xaml.cs

using System;
using System.ComponentModel;
using System.Windows;

namespace CustomControls
{
    [DesignTimeVisible(false)]
    public partial class ToolStripSplitButton : DropDownButtonBase
    {
        public event EventHandler SplitButtonClick;

        public override void OnApplyTemplate()
        {
            base.OnApplyTemplate();
            var split = Template.FindName("split", this) as UIElement;
            split.MouseDown += (s, e) => e.Handled = true;
            split.MouseLeftButtonUp += (s, e) => SplitButtonClick?.Invoke(this, e);
        }

        public ToolStripSplitButton()
        {
            InitializeComponent();
        }
    }
}