在wpf开发中，你有没有需要用到这样的场景，比如：在父窗口显示表单的输入的内容，然后再进行一些处理逻辑等，表单可以很复杂，也可以很简单，下面我就以示例代码来做一个demo展示。

1.父窗口界面展示如下：

<Window x:Class="WPFDemoMVVM.View.UserInputView"
		xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
		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"
		xmlns:local="clr-namespace:WPFDemoMVVM.View"
		mc:Ignorable="d"
		WindowStartupLocation="CenterScreen"
		Title="UserInputView" Height="450" Width="800">
	<Grid >
		<Grid.RowDefinitions>
			<RowDefinition Height="*"></RowDefinition>
			<RowDefinition Height="*"></RowDefinition>
		</Grid.RowDefinitions>
		<StackPanel Grid.Row="0" VerticalAlignment="Bottom" HorizontalAlignment="Center" Orientation="Horizontal">
			<TextBlock Text="表单结果：" VerticalAlignment="Bottom" FontSize="24"></TextBlock>
			<TextBox x:Name="UserInputTextBox" Text="{Binding UserInput, Mode=TwoWay}" Width="300" FontSize="24"></TextBox>
		</StackPanel>
		<Button Grid.Row="1" Content="在新窗口中输入" VerticalAlignment="Top" Margin="30" Background="LightGray" FontSize="24" Height="60" Command="{Binding InputCommand}"></Button>
	</Grid>
</Window>

表单子窗口如下：

<Window x:Class="WPFDemoMVVM.View.UserInputChildrenView"
		xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
		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"
		xmlns:local="clr-namespace:WPFDemoMVVM.View"
		mc:Ignorable="d"
		WindowStartupLocation="CenterOwner"
		ResizeMode="NoResize"
		WindowStyle="ToolWindow"
		Title="UserInputChildrenView" Height="300" Width="600">
	<Window.Resources>
		<Style TargetType="Button">
			<Setter Property="Padding" Value="8"></Setter>
			<Setter Property="Height" Value="60"></Setter>
			<Setter Property="Width" Value="80"></Setter>
			<Setter Property="FontSize" Value="24"></Setter>
			<Setter Property="Margin" Value="10"></Setter>
		</Style>
	</Window.Resources>

	<DockPanel Margin="10">
		<TextBlock x:Name="promptText" Text="请输入内容：" FontSize="24" DockPanel.Dock="Top"></TextBlock>
		<StackPanel HorizontalAlignment="Right" Orientation="Horizontal" DockPanel.Dock="Bottom">
			<Button x:Name="OKButton" Content="确定" Click="OKButton_Click"></Button>
			<Button x:Name="CancelButton" Content="取消" Click="CancelButton_Click" ></Button>
		</StackPanel>
		<TextBox x:Name="InputBox" TextWrapping="Wrap" Margin="2" FontSize="24"></TextBox>
	</DockPanel>
</Window>

表单子窗口后台代码：

/// <summary>
/// UserInputChildrenView.xaml 的交互逻辑
/// </summary>
public partial class UserInputChildrenView : Window
{
	public UserInputChildrenView()
	{
		InitializeComponent();
		Owner ??= Application.Current.MainWindow;
		this.InputBox.Focus();
		this.InputBox.SelectAll();
	}

	public string? UserInput { get; private set; }
	public UserInputChildrenView(string prompt, string title, string text = "") : this()
	{
		this.promptText.Text = prompt;
		this.Title = title;
		this.InputBox.Text = text;
	}
	private void OKButton_Click(object sender, RoutedEventArgs e)
	{
		this.InputBox.Text = this.InputBox.Text.Trim();
		this.DialogResult = true;
	}
	private void CancelButton_Click(object sender, RoutedEventArgs e)
	{
		this.DialogResult = false;
	}
}

2.接口服务IUserInputService和UserInputService实现：

public interface IUserInputService
{
	string RequestInputBox(string prompt, string title, string text = "");
}

实现类，用来获取表单输入的内容：

 public class UserInputService : IUserInputService
 {
	 public string RequestInputBox(string prompt, string title, string text = "")
	 {
		 var input = new UserInputChildrenView(prompt, title, text);
		 var res = input.ShowDialog();
		 if (res == true)
		 {
			 return input.InputBox.Text;
		 }
		 else
		 {
			 return null;
		 }
	 }
 }

3.新建UserInputViewModel类，通过构造函数，注入IUserInputService服务，实现调用弹窗表单输入的子窗口；

public partial class UserInputViewModel : ObservableObject
{
	private readonly IUserInputService _userInputService;
	public UserInputViewModel(IUserInputService userInputService)
	{
		_userInputService = userInputService;
	}
	
	[ObservableProperty]
	private string userInput;
	[RelayCommand]
	private void Input()
	{
		var userInput = _userInputService.RequestInputBox("请输入内容：", "用户输入", UserInput);
		if (!string.IsNullOrEmpty(userInput))
		{
			UserInput = userInput;
		}
	}
}