How to show animation while the code is being processed in an event in C# WPF

In my opinion, to continue animation indefinitely until the database operation is finished, add an attribute:

 <Storyboard x:Key="RotationBtn" RepeatBehavior="Forever">

Also remove the trigger because you will start the animation programmatically.

The lengthy database operation can be started as a background task. For example:

private void Command4_Click( object sender, RoutedEventArgs e )
{
    // start the animation
    {
        Storyboard sb = (Storyboard)FindResource( "RotationBtn" );
        Storyboard.SetTarget( sb, Command4 );
        sb.Begin( );
    }

    // start the background database operation
    var t = new Thread( ( ) =>
        {
            var MyQuery = dbms.Database.SqlQuery<DB_Cust>( "SELECT * FROM Customers" ).ToList( );

            // stop the animation and display the results
            App.Current.Dispatcher.Invoke( ( ) =>
            {
                Storyboard sb = (Storyboard)FindResource( "RotationBtn" );
                sb.Stop( );
                // . . .
            } );

        } )
    {
        IsBackground = true
    };
    t.Start( );
}

After finishing the database operation, you can stop the animation and access the elements (to display the results, for example) inside the Invoke block.

Hi,
There is a few problems with your code.

1) Threading
All code inside Command4_Click is executing in the main thread, including long running DB query execution.

       private void Command4_Click(object sender, RoutedEventArgs e) {
            // The new thread is created from the main thread.
            new Thread(() =>
            {
                // Then delegate is invoked in the main thread.
                App.Current.Dispatcher.Invoke((Action)delegate
                {
                    // This code block is executing in the main thread.
                    Storyboard sb = TryFindResource("RotationBtn") as Storyboard;
                    Storyboard.SetTarget(sb, Command4);
                    sb.Begin();
                });
            }).Start();
            // The long running operation in executing in the main thread.
            var MyQuery = dbms.Database.SqlQuery<DB_Cust>("SELECT * FROM Customers").ToList();
        }

2) Storyboard RepeatBehaviour
The storyboard animation will be played just once. In your case RepeatBehaviour property should be set to "Forever".

    <Window.Resources>
        <Storyboard x:Key="RotationBtn" RepeatBehavior="Forever">

3) EventTrigger
You are starting and stopping the animation manually and therefore event trigger should be removed.

Solution (based on your code):
XAML:

    <Window.Resources>
        <Storyboard x:Key="RotationBtn" RepeatBehavior="Forever">
            <DoubleAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.RenderTransform).(TransformGroup.Children)[2].(RotateTransform.Angle)" Storyboard.TargetName="Command4">
                <EasingDoubleKeyFrame KeyTime="0:0:1" Value="720"/>
            </DoubleAnimationUsingKeyFrames>
        </Storyboard>
    </Window.Resources>

    <Grid>
        <Button x:Name="Command4" Content="Next Stage" Margin="599,406,304,84"   Width="130" Height="37" FontSize="8" Click="Command4_Click" Background="#FFDDDDDD" BorderBrush="{x:Null}" RenderTransformOrigin="0.5,0.5">
            <Button.RenderTransform>
                <TransformGroup>
                    <ScaleTransform/>
                    <SkewTransform/>
                    <RotateTransform/>
                    <TranslateTransform/>
                </TransformGroup>
            </Button.RenderTransform>
        </Button>
    </Grid>

CS:

        private async void Command4_Click(object sender, RoutedEventArgs e) {
            // Get storyboard.
            var storyboard = GetStoryboard();
            // Start animation.
            StartAnimation(storyboard, Command4);      
            // Get customers.
            var customers = await GetCustomersAsync();
            // TODO: Process result.
            // Stop animation.
            StopAnimation(storyboard);
        }

        private async Task<List<string>> GetCustomersAsync() {
            // Simulate long running operation.
            await Task.Delay(5000);
            return new List<string> {
                "Customer 1",
                "Customer 2"
            };
        }

        private Storyboard GetStoryboard() 
        {
            return TryFindResource("RotationBtn") as Storyboard;
        }

        private void StartAnimation(Storyboard storyboard)   
        {
            Storyboard.SetTarget(storyboard, Command4);
            storyboard.Begin();
        }

        private void StopAnimation(Storyboard storyboard)
        {
            storyboard.Stop();
        }

In general it will be better to utilize full potential of WPF and .NET framework.

• TAP or TPL for asynchronous operations instead of the custom multi-threading,
• Design patterns like MVVM,
• Binding and data templates,
• Triggers instead of the code behind,
• etc.

BR,
Adnan

You begin the storyboard (at line 9 in CS Code) and never stop it, then this animation start and never stop until you close the application.
so you can Stop this animation on any event (eg: MouseLeave) :

        private void Command4_MouseLeave(object sender, System.Windows.Input.MouseEventArgs e)
        {
            new Thread(() =>
            {
                App.Current.Dispatcher.Invoke((Action)delegate
                {
                    Storyboard sb = TryFindResource("RotationBtn") as Storyboard;
                    Storyboard.SetTarget(sb, Command4);
                    sb.Stop();
                });
            }).Start();
        }