C# 停止动画并使用开关盒启动另一个动画

我有一个动画，它在加载时开始：

<Grid.Triggers>
        <EventTrigger RoutedEvent= "Canvas.Loaded">
            <BeginStoryboard>
                <Storyboard x:Name="sb1" RepeatBehavior="Forever">
                    <DoubleAnimation Name="earth" From="0" To="-360" Duration="0:0:10" AutoReverse="False" Storyboard.TargetName="rotation" Storyboard.TargetProperty="Angle" />
                </Storyboard>
            </BeginStoryboard>
        </EventTrigger>           
    </Grid.Triggers>

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你犯了什么错误？FindName（）是否返回null？它只是不工作，动画没有停止，第二个动画也没有开始。我需要先停止，然后当用户输入一个case时触发第二个动画，但我不知道如何在

<EventTrigger RoutedEvent= ""><!--switch case "AMERICA" -->
            <BeginStoryboard>
                <Storyboard x:Name="sb2">
                    <DoubleAnimation Name="america" To="0" Duration="0:0:5" AutoReverse="False" Storyboard.TargetName="rotation" Storyboard.TargetProperty="Angle" />
                </Storyboard>
            </BeginStoryboard>
        </EventTrigger>      

 switch (e.Result.Semantics.Value.ToString())
            {

                case "AMERICA":
                    americaSpan.Foreground = Brushes.DeepSkyBlue;
                    americaSpan.FontWeight = FontWeights.Bold;

                    Storyboard storyBoard1 = (Storyboard)FindName("sb1");
                    Storyboard storyBoard2 = (Storyboard)FindName("sb2");
                    storyBoard1.Stop();
                    storyBoard2.Begin();

                    break;   

            }