File: Core\CSharp\System\Windows\Input\MouseButtonEventHandler.cs
Project: wpf\src\PresentationCore.csproj (PresentationCore)

using System;
namespace System.Windows.Input
{
    /// <summary>
    ///     The delegate to use for handlers that receive MouseButtonEventArgs.
    /// </summary>
    public delegate void MouseButtonEventHandler(object sender, MouseButtonEventArgs e);
}