1、效果演示

2、在Views中创建WindowDemo.axaml如下图

WindowDemo.axaml代码如下

<Window xmlns="https://github.com/avaloniaui"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        mc:Ignorable="d" d:DesignWidth="200" d:DesignHeight="200"
        Width="200"
        Height="200"
        x:Class="AvaloniaStepByStepLearning.WindowDemo"
        WindowStartupLocation="CenterOwner"
        Title="WindowDemo">

    <Button x:Name="btnClose" Click="BtnClose_OnClick" HorizontalAlignment="Center" VerticalAlignment="Center" Content="关闭窗口"/>
</Window>

 WindowDemo.axaml.cs代码如下：

using Avalonia;
using Avalonia.Controls;
using Avalonia.Interactivity;
using Avalonia.Markup.Xaml;

namespace AvaloniaStepByStepLearning;

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

    private void BtnClose_OnClick(object? sender, RoutedEventArgs e)
    {
        Close("返回的数据");
    }
}

3、示例代码步骤

3.1、MainView.axaml添加代码如下

		<Button HorizontalAlignment="Center" Content="Menu/菜单">
			<Button.Flyout>
				<MenuFlyout>
					<MenuItem x:Name="MItOpen" Header="打开" Click="MenuItem_OnClick"/>
					<MenuItem Header="-"/>
					<MenuItem x:Name="MItClose" Header="关闭" Click="MenuItem_OnClick"/>
                    <MenuItem Header="-"/>
                    <MenuItem x:Name="MItHideAndShow" Header="隐藏/显示" Click="MenuItem_OnClick"/>
                    
				</MenuFlyout>
			</Button.Flyout>
		</Button>

        <Button x:Name="btnGetString" HorizontalAlignment="Center" Content="MenuDialog" Margin="0 15 0 0">
            <Button.Flyout>
                <MenuFlyout>
                    <MenuItem x:Name="MItOpenDialog" Header="打开无返回值" Click="MenuItem_OnClick"/>
                    <MenuItem x:Name="MItOpenGetDialog" Header="打开获取返回值" Click="MenuItem_OnClick"/>
					<MenuItem Header="-"/>
                    <MenuItem x:Name="MItCloseDialog" Header="关闭" Click="MenuItem_OnClick"/>
                </MenuFlyout>
            </Button.Flyout>
        </Button>

3.2、MainView.axaml.cs添加代码如下

    public Window currenWindow
    {
        get
        {
            return GetParentWindow();
        }
    }

    public Window GetParentWindow()
    {
        if (Avalonia.Application.Current.ApplicationLifetime is IClassicDesktopStyleApplicationLifetime desktop)
        {
            return desktop.MainWindow;
        }
        else
        {
            return null;
        }
    }

    private WindowDemo _windowDemo;
    private async void MenuItem_OnClick(object? sender, RoutedEventArgs e)
    {
        MenuItem _menuItem = (MenuItem)sender;

        switch (_menuItem.Name)
        {
            case "MItOpen":
                _windowDemo = new WindowDemo();
                _windowDemo.Show();
                break;
            case "MItClose":
                _windowDemo.Close();
                _windowDemo = null;
                break;
            case "MItHideAndShow":
                if (_windowDemo==null)
                {
                    _windowDemo = new WindowDemo();
                }
                _windowDemo.Hide();
                Thread.Sleep(3000);
                _windowDemo.Show();
                break;
            case "MItOpenDialog":
                if (_windowDemo!=null)
                {
                    _windowDemo.Close();
                    _windowDemo = null;
                }
                _windowDemo = new WindowDemo();
                await _windowDemo.ShowDialog(currenWindow);
                break;
            case "MItOpenGetDialog":
                _windowDemo = new WindowDemo();
                var str=await _windowDemo.ShowDialog<string>(currenWindow);
                btnGetString.Content = str;
                Debug.WriteLine(str);
                break;
            case "MItCloseDialog":
                if (_windowDemo!=null)
                {
                    _windowDemo.Close();
                    _windowDemo = null;
                }
                break;
            default:
                break;
        }
    }

3.3、Avalonia 获取MainWindow.axaml 代码如下

    public Window currenWindow
    {
        get
        {
            return GetParentWindow();
        }
    }

    public Window GetParentWindow()
    {
        if (Avalonia.Application.Current.ApplicationLifetime is IClassicDesktopStyleApplicationLifetime desktop)
        {
            return desktop.MainWindow;
        }
        else
        {
            return null;
        }
    }