首先新建一个WPF工程，在主界面添加一个按钮，并给按钮添加点击事件button1_Click，然后新建一个用于测试弹出位置的窗口TestWindow。
1、在屏幕中间显示，设置window.WindowStartupLocation = WindowStartupLocation.CenterScreen;
private void button1_Click(object sender, RoutedEventArgs e)
{
TestWindow window = new TestWindow();
window.WindowStartupLocation = WindowStartupLocation.CenterScreen;
window.ShowDialog();
}
2、在父窗口中间显示，
设置window.WindowStartupLocation = WindowStartupLocation.CenterOwner;，并指定Owner。
private void button1_Click(object sender, RoutedEventArgs e)
{
TestWindow window = new TestWindow();
window.WindowStartupLocation = WindowStartupLocation.CenterOwner;
window.Owner = this;
window.ShowDialog();
}
3、在任意位置显示，设置window.WindowStartupLocation = WindowStartupLocation.Manual;并制定窗口的Left和Top坐标。
private void button1_Click(object sender, RoutedEventArgs e)
{
TestWindow window = new TestWindow();
window.WindowStartupLocation = WindowStartupLocation.Manual;
window.Left = ;
window.Top = ;
window.ShowDialog();
}