wpfMediaPlayer.GotFocus += new EventHandler(wpfMediaPlayer_MouseEnter);

重写此方法即可

<WindowsFormsHost Name="wphWMP" MaxHeight="607" MaxWidth="1082" Panel.ZIndex="3" Height="532" Width="1029" Canvas.Left="25" Canvas.Top="27">
                <mediaControl:AxWindowsMediaPlayer x:Name="wpfMediaPlayer" TabStop="True" Dock="Fill" AccessibleRole="None" />
            </WindowsFormsHost>

 

 

  /// <summary>
        /// 初始化视频
        /// </summary>
        private void InitVideo()
        {
            wpfMediaPlayer.uiMode = "None";
            wpfMediaPlayer.enableContextMenu = false;
            string[] videoList = VideoInfoBiz.videoList;
            IWMPPlaylist playList = this.wpfMediaPlayer.currentPlaylist;
            foreach (string url in videoList)
            {
                IWMPMedia media = this.wpfMediaPlayer.newMedia(url);
                playList.appendItem(media);
            }
            this.wpfMediaPlayer.currentPlaylist = playList;
            this.wpfMediaPlayer.settings.setMode("loop", true);
            wpfMediaPlayer.GotFocus += new EventHandler(wpfMediaPlayer_MouseEnter);
        }

        private void wpfMediaPlayer_MouseEnter(object sender, EventArgs e)
        {
            if (this.wpfMediaPlayer.fullScreen == true)
            {
                this.wpfMediaPlayer.fullScreen = false;
            }
        }