<Window x:Class="Demo010.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="149" Width="296">
    <Window.Resources>
        <TextBlock x:Key="Res1" Text="海上生明月" />
        <TextBlock x:Key="Res2" Text="海上生明月" />
    </Window.Resources>
    <StackPanel>
        <Button Margin="5,5,5,0" Content="{StaticResource Res1}" />
        <Button Margin="5,5,5,0" Content="{DynamicResource Res2}" />
        <Button Margin="5,5,5,0" Content="Update" Click="UpdateRes_Click" />
    </StackPanel>
</Window>

private void UpdateRes_Click(object sender, RoutedEventArgs e)
{
    this.Resources["Res1"] = new TextBlock() { Text = "天涯共此时" };
    this.Resources["Res2"] = new TextBlock() { Text = "天涯共此时" };
}