回答編集履歴

  ちょっとやりたいことが見えないので外しているかもしれませんが、３パターンで`BeginStoryboard`しました。

  肝心のアニメーションがないので、色を変えるだけのつまらないアニメーションになってしまいました^^;

 

  * 朝 コードビハインドでキック

  * 昼 `EventTrigger`でキック

  * 夜 `DataTrigger`でキック

 

  <Window

  x:Class="Questions298961.MainWindow"

  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

  xmlns:local="clr-namespace:Questions298961"

  x:Name="window"

  Title="MainWindow"

  Width="450"

  Height="450">

 

  <Window.Resources>

  <!-- コードビハインドでキック -->

  <Storyboard x:Key="MorningAnimation">

  <ColorAnimationUsingKeyFrames Storyboard.TargetName="window" Storyboard.TargetProperty="(Panel.Background).(SolidColorBrush.Color)">

  <EasingColorKeyFrame KeyTime="0:0:1" Value="#FFFFA400" />

  </ColorAnimationUsingKeyFrames>

  </Storyboard>

  <!-- EventTriggerでキック -->

  <Storyboard x:Key="EveningAnimation">

  <ColorAnimationUsingKeyFrames Storyboard.TargetName="window" Storyboard.TargetProperty="(Panel.Background).(SolidColorBrush.Color)">

  <EasingColorKeyFrame KeyTime="0:0:1" Value="#FF0388FF" />

  </ColorAnimationUsingKeyFrames>

  </Storyboard>

  <!-- DataTriggerでキック -->

  <Storyboard x:Key="NightAnimation">

  <ColorAnimationUsingKeyFrames Storyboard.TargetProperty="(Panel.Background).(SolidColorBrush.Color)">

  <EasingColorKeyFrame KeyTime="0:0:1" Value="#FF02067A" />

  </ColorAnimationUsingKeyFrames>

  </Storyboard>

  <Style TargetType="{x:Type Button}">

  <Setter Property="Width" Value="100" />

  <Setter Property="Height" Value="50" />

  <Setter Property="FontSize" Value="24" />

  </Style>

  </Window.Resources>

 

  <Window.Style>

  <Style>

  <Style.Triggers>

  <DataTrigger Binding="{Binding Now}" Value="{x:Static local:Period.NIGHT}">

  <DataTrigger.EnterActions>

  <BeginStoryboard Storyboard="{StaticResource NightAnimation}" />

  </DataTrigger.EnterActions>

  </DataTrigger>

  </Style.Triggers>

  </Style>

  </Window.Style>

 

  <Canvas>

  <TextBlock

  Canvas.Left="111"

  Canvas.Top="98"

  Width="219"

  Height="100"

  FontSize="36"

  Text="{Binding Path=Phrase}"

  TextWrapping="Wrap" />

  <Button

  Canvas.Left="30"

  Canvas.Top="250"

  Click="Click_Morning"

  Content="朝" />

  <Button

  Canvas.Left="170"

  Canvas.Top="250"

  Click="Click_Evening"

  Content="昼">

  <Button.Triggers>

  <EventTrigger RoutedEvent="Button.Click">

  <BeginStoryboard Storyboard="{StaticResource EveningAnimation}" />

  </EventTrigger>

  </Button.Triggers>

  </Button>

  <Button

  Canvas.Left="310"

  Canvas.Top="250"

  Click="Click_Night"

  Content="夜" />

  <Button

  Canvas.Left="170"

  Canvas.Top="325"

  Click="Click_Greeting"

  Content="あいさつ" />

  </Canvas>

  </Window>

  ```

 

  using System.ComponentModel;

  using System.Windows;

  using System.Windows.Media.Animation;

 

  namespace Questions298961

  {

  public enum Period { MORNING, EVENING, NIGHT };

 

  public partial class MainWindow : Window

  {

  private readonly GreetingPhrase ph = new GreetingPhrase();

 

  public MainWindow()

  {

  InitializeComponent();

  DataContext = ph;

  }

 

  private void Click_Morning(object sender, RoutedEventArgs e)

  {

  ph.Now = Period.MORNING;

  var sb = FindResource("MorningAnimation") as Storyboard;

  BeginStoryboard(sb);

  }

 

  private void Click_Evening(object sender, RoutedEventArgs e) => ph.Now = Period.EVENING;

 

  private void Click_Night(object sender, RoutedEventArgs e) => ph.Now = Period.NIGHT;

 

  private void Click_Greeting(object sender, RoutedEventArgs e) => ph.ChangePhrase();

  }

 

  public class GreetingPhrase : INotifyPropertyChanged

  {

  public string Phrase { get; set; }

 

  private Period _Now;

  public Period Now

  {

  get => _Now;

  set

  {

  _Now = value;

  RaiseProeprtyChanged(nameof(Now));

  }

  }

 

  public void ChangePhrase()

  {

  switch(Now)

  {

  case Period.MORNING:

  Phrase = "おはよう！";

  break;

  case Period.EVENING:

  Phrase = "こんにちは！";

  break;

  case Period.NIGHT:

  Phrase = "こんばんは！";

  break;

  }

  RaiseProeprtyChanged(nameof(Phrase));

  }

 

  #region INotifyPropertyChanged の実装

  public event PropertyChangedEventHandler PropertyChanged;

  private void RaiseProeprtyChanged(string propertyName) => PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));

  #endregion

  }

  }

  ```