MainWindow.xaml

<Window x:Class="Karno.Xac.Sample.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:ei="http://schemas.microsoft.com/expression/2010/interactions"
        xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
        xmlns:sample="clr-namespace:Karno.Xac.Sample"
        Title="MainWindow"
        Width="400"
        Height="400">
    <Window.DataContext>
        <sample:MainWindowViewModel />
    </Window.DataContext>
    <i:Interaction.Triggers>
        <i:EventTrigger EventName="Loaded">
            <ei:CallMethodAction MethodName="Loaded" TargetObject="{Binding}" />
        </i:EventTrigger>
    </i:Interaction.Triggers>
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto" />
            <RowDefinition />
        </Grid.RowDefinitions>
        <StackPanel Orientation="Horizontal">
            <TextBlock FontSize="32" Text="時間: " />
            <TextBlock FontSize="32" Text="{Binding CurrentTimeSec}" />
        </StackPanel>
        <ItemsControl Grid.Row="1"
                      AllowDrop="True"
                      ItemsSource="{Binding Collection}">
            <i:Interaction.Behaviors>
                <sample:DragAcceptBehavior Description="{Binding Description}" />
            </i:Interaction.Behaviors>
            <ItemsControl.ItemsPanel>
                <ItemsPanelTemplate>
                    <WrapPanel />
                </ItemsPanelTemplate>
            </ItemsControl.ItemsPanel>
            <ItemsControl.ItemTemplate>
                <DataTemplate>
                    <Border Width="120"
                            Height="120"
                            Background="#FF1BA1E2"
                            BorderBrush="White"
                            BorderThickness="3">
                        <i:Interaction.Behaviors>
                            <sample:DragStartBehavior AllowedEffects="Move" DragDropData="{Binding}" />
                        </i:Interaction.Behaviors>
                        <TextBlock HorizontalAlignment="Center"
                                   VerticalAlignment="Center"
                                   FontSize="60"
                                   Foreground="White"
                                   Text="{Binding}"
                                   TextAlignment="Center" />
                    </Border>
                </DataTemplate>
            </ItemsControl.ItemTemplate>
        </ItemsControl>
    </Grid>
</Window>