实现效果图：
1、创建一个用户控件，实现动画旋转：
<UserControl x:Class="K.Controls.Controls.LoadingWait"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:local="clr-namespace:K.Controls.Controls"
mc:Ignorable="d"
>
<UserControl.Background>
<SolidColorBrush Color="Transparent"/>
</UserControl.Background>
<Grid Width="36" Height="36">
<Grid.Resources>
<DrawingBrush x:Key="brush" Stretch="None" AlignmentX="Center" AlignmentY="Top">
<DrawingBrush.Drawing>
<GeometryDrawing Brush="{DynamicResource LoadingWaitBrush}">
<GeometryDrawing.Geometry>
<EllipseGeometry RadiusX="2" RadiusY="7"/>
</GeometryDrawing.Geometry>
</GeometryDrawing>
</DrawingBrush.Drawing>
</DrawingBrush>
</Grid.Resources>
<Rectangle x:Name="r01" Fill="{StaticResource brush}" Opacity="1" RenderTransformOrigin="0.5,0.5">
<Rectangle.RenderTransform>
<RotateTransform Angle="0"/>
</Rectangle.RenderTransform>
</Rectangle>
<Rectangle x:Name="r02" Fill="{StaticResource brush}" Opacity="1" RenderTransformOrigin="0.5,0.5">
<Rectangle.RenderTransform>
<RotateTransform Angle="30"/>
</Rectangle.RenderTransform>
</Rectangle>
<Rectangle x:Name="r03" Fill="{StaticResource brush}" Opacity="1" RenderTransformOrigin="0.5,0.5">
<Rectangle.RenderTransform>
<RotateTransform Angle="60"/>
</Rectangle.RenderTransform>
</Rectangle>
<Rectangle x:Name="r04" Fill="{StaticResource brush}" Opacity="1" RenderTransformOrigin="0.5,0.5">
<Rectangle.RenderTransform>
<RotateTransform Angle="90"/>
</Rectangle.RenderTransform>
</Rectangle>
<Rectangle x:Name="r05" Fill="{StaticResource brush}" Opacity="1" RenderTransformOrigin="0.5,0.5">
<Rectangle.RenderTransform>
<RotateTransform Angle="120"/>
</Rectangle.RenderTransform>
</Rectangle>
<Rectangle x:Name="r06" Fill="{StaticResource brush}" Opacity="1" RenderTransformOrigin="0.5,0.5">
<Rectangle.RenderTransform>
<RotateTransform Angle="150"/>
</Rectangle.RenderTransform>
</Rectangle>
<Rectangle x:Name="r07" Fill="{StaticResource brush}" Opacity="1" RenderTransformOrigin="0.5,0.5">
<Rectangle.RenderTransform>
<RotateTransform Angle="180"/>
</Rectangle.RenderTransform>
</Rectangle>
<Rectangle x:Name="r08" Fill="{StaticResource brush}" Opacity="1" RenderTransformOrigin="0.5,0.5">
<Rectangle.RenderTransform>
<RotateTransform Angle="210"/>
</Rectangle.RenderTransform>
</Rectangle>
<Rectangle x:Name="r09" Fill="{StaticResource brush}" Opacity="1" RenderTransformOrigin="0.5,0.5">
<Rectangle.RenderTransform>
<RotateTransform Angle="240"/>
</Rectangle.RenderTransform>
</Rectangle>
<Rectangle x:Name="r10" Fill="{StaticResource brush}" Opacity="1" RenderTransformOrigin="0.5,0.5">
<Rectangle.RenderTransform>
<RotateTransform Angle="270"/>
</Rectangle.RenderTransform>
</Rectangle>
<Rectangle x:Name="r11" Fill="{StaticResource brush}" Opacity="1" RenderTransformOrigin="0.5,0.5">
<Rectangle.RenderTransform>
<RotateTransform Angle="300"/>
</Rectangle.RenderTransform>
</Rectangle>
<Rectangle x:Name="r12" Fill="{StaticResource brush}" Opacity="1" RenderTransformOrigin="0.5,0.5">
<Rectangle.RenderTransform>
<RotateTransform Angle="330"/>
</Rectangle.RenderTransform>
</Rectangle>
<Grid.Triggers>
<EventTrigger RoutedEvent="Grid.Loaded">
<BeginStoryboard>
<Storyboard RepeatBehavior="Forever">
<DoubleAnimation Storyboard.TargetName="r01" Storyboard.TargetProperty="Opacity" AutoReverse="True" Duration="0:0:0.08333" BeginTime="0:0:0.00000" To="0"/>
<DoubleAnimation Storyboard.TargetName="r02" Storyboard.TargetProperty="Opacity" AutoReverse="True" Duration="0:0:0.08333" BeginTime="0:0:0.08333" To="0"/>
<DoubleAnimation Storyboard.TargetName="r03" Storyboard.TargetProperty="Opacity" AutoReverse="True" Duration="0:0:0.08333" BeginTime="0:0:0.16666" To="0"/>
<DoubleAnimation Storyboard.TargetName="r04" Storyboard.TargetProperty="Opacity" AutoReverse="True" Duration="0:0:0.08333" BeginTime="0:0:0.24999" To="0"/>
<DoubleAnimation Storyboard.TargetName="r05" Storyboard.TargetProperty="Opacity" AutoReverse="True" Duration="0:0:0.08333" BeginTime="0:0:0.33332" To="0"/>
<DoubleAnimation Storyboard.TargetName="r06" Storyboard.TargetProperty="Opacity" AutoReverse="True" Duration="0:0:0.08333" BeginTime="0:0:0.41665" To="0"/>
<DoubleAnimation Storyboard.TargetName="r07" Storyboard.TargetProperty="Opacity" AutoReverse="True" Duration="0:0:0.08333" BeginTime="0:0:0.49998" To="0"/>
<DoubleAnimation Storyboard.TargetName="r08" Storyboard.TargetProperty="Opacity" AutoReverse="True" Duration="0:0:0.08333" BeginTime="0:0:0.58331" To="0"/>
<DoubleAnimation Storyboard.TargetName="r09" Storyboard.TargetProperty="Opacity" AutoReverse="True" Duration="0:0:0.08333" BeginTime="0:0:0.66664" To="0"/>
<DoubleAnimation Storyboard.TargetName="r10" Storyboard.TargetProperty="Opacity" AutoReverse="True" Duration="0:0:0.08333" BeginTime="0:0:0.74997" To="0"/>
<DoubleAnimation Storyboard.TargetName="r11" Storyboard.TargetProperty="Opacity" AutoReverse="True" Duration="0:0:0.08333" BeginTime="0:0:0.83330" To="0"/>
<DoubleAnimation Storyboard.TargetName="r12" Storyboard.TargetProperty="Opacity" AutoReverse="True" Duration="0:0:0.08333" BeginTime="0:0:0.91663" To="0"/>
</Storyboard>
</BeginStoryboard>
</EventTrigger>
</Grid.Triggers>
</Grid>
</UserControl>
2、资源文件中设置Loading的颜色------Brush="{DynamicResource LoadingWaitBrush}"
<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:cal="clr-namespace:K.Controls.Controls"
xmlns:o="http://schemas.microsoft.com/winfx/2006/xaml/presentation/options"
>
<!--加载等待-->
<SolidColorBrush o:Freeze="True" x:Key="LoadingWaitBrush" Color="#FFFFFF"/>
</ResourceDictionary>
3、其他界面引用上述用户控件
<controls:PopupEx IsOpen="{Binding ShowLoading}" PlacementTarget="{Binding ElementName=bdMain}" Placement="Center" VerticalAlignment="Center" VerticalOffset="0" AllowsTransparency="True" StaysOpen="True">
<Grid Background="{DynamicResource PayVipCouponsLoadingBackground}" Width="{Binding ElementName=bdMain,Path=ActualWidth}" Height="{Binding ElementName=bdMain,Path=ActualHeight}" >
<StackPanel Orientation="Horizontal" VerticalAlignment="Center" HorizontalAlignment="Center">
<controls:LoadingWait Width="48" Height="48"/>
<TextBlock FontSize="26" Foreground="{DynamicResource PayVipCouponsLoadingForBrush}" VerticalAlignment="Center" HorizontalAlignment="Center" Text="请稍等，正在为您计算优惠券" Margin="15,0,0,0"/>
</StackPanel>
</Grid>
</controls:PopupEx>