using Microsoft.Practices.Prism.Interactivity.InteractionRequest;

<Window x:Class="ChildWindowDemo.ChildWindow.ChildWindow"xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"  xmlns:ei="http://schemas.microsoft.com/expression/2010/interactions"Width="300" Height="150" Title="{Binding Title}"x:Name="confirmationWindow" Topmost="True" WindowStyle="ToolWindow" WindowStartupLocation="CenterScreen"><Grid x:Name="LayoutRoot" Margin="2"><Grid.RowDefinitions><RowDefinition /><RowDefinition Height="Auto" /></Grid.RowDefinitions><ContentControl HorizontalAlignment="Stretch" VerticalAlignment="Stretch" Grid.Row="0" Content="{Binding Content}"/><Button Content="Cancel" Width="75" Height="23" HorizontalAlignment="Right" Margin="0,12,0,0" Grid.Row="1"><i:Interaction.Triggers><i:EventTrigger EventName="Click"><ei:CallMethodAction TargetObject="{Binding ElementName=confirmationWindow}" MethodName="Close"/></i:EventTrigger></i:Interaction.Triggers></Button><Button Content="OK" Width="75" Height="23" HorizontalAlignment="Right" Margin="0,12,79,0" Grid.Row="1"><i:Interaction.Triggers><i:EventTrigger EventName="Click"><ei:ChangePropertyAction PropertyName="Confirmed" TargetObject="{Binding}" Value="True"/><ei:CallMethodAction TargetObject="{Binding ElementName=confirmationWindow}" MethodName="Close"/></i:EventTrigger></i:Interaction.Triggers></Button></Grid>
</Window>

    public class ChildWindowActionBase : TriggerAction<FrameworkElement>{protected override void Invoke(object parameter){var arg = parameter as InteractionRequestedEventArgs;if (arg == null)return;var windows = this.GetChildWindow(arg.Context);var callback = arg.Callback;EventHandler handler = null;handler =(o, e) =>{windows.Closed -= handler;callback();};windows.Closed += handler;windows.ShowDialog();}Window GetChildWindow(Notification notification){var childWindow = this.CreateDefaultWindow(notification);childWindow.DataContext = notification;return childWindow;}Window CreateDefaultWindow(Notification notification){return (Window)new ChildWindow.ChildWindow();}}   

<Window x:Class="ChildWindowDemo.MainWindow"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:prism="http://www.codeplex.com/prism"xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"xmlns:local="clr-namespace:ChildWindowDemo"Title="MainWindow" Height="200" Width="300"><i:Interaction.Triggers><prism:InteractionRequestTrigger SourceObject="{Binding ConfirmationRequest, Mode=OneWay}"><local:ChildWindowActionBase/></prism:InteractionRequestTrigger></i:Interaction.Triggers><Grid><Button Command="{Binding RaiseConfirmation}" Content="Click Me !" HorizontalAlignment="Left" Margin="29,31,0,0" VerticalAlignment="Top" Width="217" Height="55"/><TextBlock HorizontalAlignment="Left" Margin="29,106,0,0" TextWrapping="Wrap" Text="{Binding ConfirmationResult}" VerticalAlignment="Top"/></Grid>
</Window>

    public class MainWindowViewModel : NotificationObject{public MainWindowViewModel(){this.RaiseConfirmation = new DelegateCommand(this.OnRaiseConfirmation);this.ConfirmationRequest = new InteractionRequest<Confirmation>();}public InteractionRequest<Confirmation> ConfirmationRequest { get; private set; }public DelegateCommand RaiseConfirmation { get; private set; }private string result;public string ConfirmationResult{get { return result; }set{result = value;this.RaisePropertyChanged(() => this.ConfirmationResult);}}private void OnRaiseConfirmation(){this.ConfirmationRequest.Raise(new Confirmation { Content = "是否确认", Title = "子窗体" },(cb) => { ConfirmationResult = cb.Confirmed ? "确认" : "取消"; });}      }