Use Window Activated and Deactivated event to control a media file

   
  


<Window x:Class="CustomMediaPlayerWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="Custom Media Player"
    Activated="window_Activated"
    Deactivated="window_Deactivated"
    Closing="window_Closing">
  <DockPanel>
    <Menu DockPanel.Dock="Top">
      <MenuItem Header="_File">
        <MenuItem Header="_Exit" Click="exitMenu_Click" />
      </MenuItem>
    </Menu>
    <StackPanel DockPanel.Dock="Top" Orientation="Horizontal" HorizontalAlignment="Center">
      <Button Name="playButton" Click="playButton_Click">Play</Button>
      <Button Name="clickButton" Click="stopButton_Click">Stop</Button>
    </StackPanel>
    <MediaElement Stretch="Fill" Name="mediaElement" LoadedBehavior="Manual" Source="numbers.wmv" />
  </DockPanel>
</Window>
//File:Window.xaml.cs
using System;
using System.ComponentModel;
using System.Windows;

public partial class CustomMediaPlayerWindow : Window
{
    public CustomMediaPlayerWindow()
    {
        InitializeComponent();
    }

    bool isMediaElementPlaying;
    
    void playButton_Click(object sender, RoutedEventArgs e) {
        this.mediaElement.Play();
        this.isMediaElementPlaying = true;
    }

    void stopButton_Click(object sender, RoutedEventArgs e)
    {
        this.mediaElement.Stop();
        this.isMediaElementPlaying = false;
    }

    void window_Activated(object sender, EventArgs e)
    {
        if( this.isMediaElementPlaying ) this.mediaElement.Play();
    }

    void window_Deactivated(object sender, EventArgs e)
    {
        if (this.isMediaElementPlaying) this.mediaElement.Pause();
    }

    void exitMenu_Click(object sender, RoutedEventArgs e)
    {
        this.Close();
    }

    void window_Closing(object sender, CancelEventArgs e)
    {
        if (this.isMediaElementPlaying)
        {
            e.Cancel = true;
        }
    }
}