What you see there is a highly customized busy indicator. The busy indicator itself uses a progress bar to show the progress (the one that looks like a slider).
The implementation of the control is rather simple. Here is the XAML we use.
The content (the small icons and the GridView text you see while it is loading)
<ControlTemplatex:Key="ProgressBarTemplate"TargetType="telerik:RadProgressBar">
<Grid>
<VisualStateManager.VisualStateGroups>
<VisualStateGroupx:Name="OrientationStates">
<VisualStatex:Name="Horizontal">
<Storyboard>
<ObjectAnimationUsingKeyFramesDuration="00:00:00"Storyboard.TargetProperty="(LayoutTransformControl.LayoutTransform)"Storyboard.TargetName="transformationRoot">
<DiscreteObjectKeyFrameKeyTime="00:00:00">
<DiscreteObjectKeyFrame.Value>
<RotateTransformAngle="0"/>
</DiscreteObjectKeyFrame.Value>
</DiscreteObjectKeyFrame>
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
<VisualStatex:Name="Vertical">
<Storyboard>
<ObjectAnimationUsingKeyFramesDuration="00:00:00"Storyboard.TargetProperty="(LayoutTransformControl.LayoutTransform)"Storyboard.TargetName="transformationRoot">
<DiscreteObjectKeyFrameKeyTime="00:00:00">
<DiscreteObjectKeyFrame.Value>
<RotateTransformAngle="-90"/>
</DiscreteObjectKeyFrame.Value>
</DiscreteObjectKeyFrame>
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
</VisualStateGroup>
<VisualStateGroupx:Name="CommonStates">
<VisualStatex:Name="Determinate"/>
<VisualStatex:Name="Indeterminate">
<StoryboardRepeatBehavior="Forever">
<ObjectAnimationUsingKeyFramesDuration="00:00:00"Storyboard.TargetProperty="(UIElement.Visibility)"Storyboard.TargetName="IndeterminateRoot">
<DiscreteObjectKeyFrameKeyTime="00:00:00"Value="Visible"/>
</ObjectAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFramesDuration="00:00:00"Storyboard.TargetProperty="(UIElement.Visibility)"Storyboard.TargetName="DeterminateRoot">
<DiscreteObjectKeyFrameKeyTime="00:00:00"Value="Collapsed"/>
</ObjectAnimationUsingKeyFrames>
<DoubleAnimationUsingKeyFramesStoryboard.TargetProperty="(Shape.Fill).(LinearGradientBrush.Transform).(TransformGroup.Children)[0].X"Storyboard.TargetName="IndeterminateGradientFill">
<SplineDoubleKeyFrameKeyTime="0"Value="0"/>
<SplineDoubleKeyFrameKeyTime="00:00:.5"Value="20"/>
</DoubleAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
</VisualStateGroup>
</VisualStateManager.VisualStateGroups>
<telerik:LayoutTransformControlx:Name="transformationRoot">
<Gridx:Name="Root">
<Borderx:Name="ProgressBarTrack"BorderThickness="{TemplateBinding BorderThickness}"Background="Transparent"/>
<Gridx:Name="ProgressBarRootGrid">
<Borderx:Name="ProgressBarRootGradient"BorderThickness="{TemplateBinding BorderThickness}"Margin="{TemplateBinding BorderThickness}"Canvas.ZIndex="1"/>
<Gridx:Name="IndeterminateRoot"Visibility="Collapsed">
<Borderx:Name="IndeterminateSolidFill"Background="{TemplateBinding Foreground}"Margin="{TemplateBinding BorderThickness}"Opacity="1"RenderTransformOrigin="0.5,0.5"/>
<Rectanglex:Name="IndeterminateGradientFill"Margin="{TemplateBinding BorderThickness}"Opacity="0.7"RadiusY="1"RadiusX="1">
<Rectangle.Fill>
<LinearGradientBrushEndPoint="0,1"MappingMode="Absolute"SpreadMethod="Repeat"StartPoint="20,1">
<LinearGradientBrush.Transform>
<TransformGroup>
<TranslateTransformX="0"/>
<SkewTransformAngleX="-30"/>
</TransformGroup>
</LinearGradientBrush.Transform>
<GradientStopColor="#CCFFFFFF"Offset="0"/>
<GradientStopColor="#00FFFFFF"Offset=".50"/>
<GradientStopColor="#CCFFFFFF"Offset="1.10"/>
</LinearGradientBrush>
</Rectangle.Fill>
</Rectangle>
</Grid>
<Gridx:Name="DeterminateRoot">
<Grid.ColumnDefinitions>
<ColumnDefinitionWidth="Auto"/>
<ColumnDefinitionWidth="Auto"/>
<ColumnDefinitionWidth="*"/>
</Grid.ColumnDefinitions>
<Rectanglex:Name="SkipValueSpacer"Fill="Transparent"Height="1"Width="0"/>
<Rectanglex:Name="ProgressBarIndicator"Grid.Column="1"Fill="{TemplateBinding Foreground}"HorizontalAlignment="Left"StrokeThickness="0"VerticalAlignment="Center"Height="4"/>
<GridGrid.Column="1"HorizontalAlignment="Right"RenderTransformOrigin="0.5,0.5"VerticalAlignment="Center"Height="14"Width="32">
<Grid.Background>
<LinearGradientBrushEndPoint="0.5,1"StartPoint="0.5,0">
<GradientStopColor="#FF137CB5"Offset="0"/>
<GradientStopColor="#FF2CB2FB"Offset="1"/>
</LinearGradientBrush>
</Grid.Background>
<StackPanelOrientation="Horizontal"HorizontalAlignment="Center"VerticalAlignment="Center">
<TextBlockTextWrapping="Wrap"Text="{Binding Value, RelativeSource={RelativeSource TemplatedParent}}"Foreground="White"HorizontalAlignment="Center"VerticalAlignment="Center"FontSize="9"/>
<TextBlockTextWrapping="Wrap"Text="%"Foreground="White"FontSize="10"HorizontalAlignment="Center"VerticalAlignment="Center"/>
</StackPanel>
<Pathx:Name="stripe_bend_Copy"Data="M5,0 L5,5 L0,5 z"HorizontalAlignment="Left"Margin="-6,0,0,0"Stretch="Fill"StrokeThickness="0"Width="6"UseLayoutRounding="False"Height="5"VerticalAlignment="Bottom"RenderTransformOrigin="0.5,0.5">
<Path.RenderTransform>
<CompositeTransformScaleY="-1"/>
</Path.RenderTransform>
<Path.Fill>
<LinearGradientBrushEndPoint="0.5,1"StartPoint="0.5,0">
<GradientStopColor="#FF004872"Offset="1"/>
<GradientStopColor="#FF197BAD"/>
</LinearGradientBrush>
</Path.Fill>
</Path>
</Grid>
</Grid>
</Grid>
</Grid>
</telerik:LayoutTransformControl>
</Grid>
</ControlTemplate>
<Stylex:Key="ProgressBarStyle"TargetType="telerik:RadProgressBar">
<SetterProperty="Maximum"Value="100"/>
<SetterProperty="Orientation"Value="Horizontal"/>
<SetterProperty="IsTabStop"Value="False"/>
<SetterProperty="Template"Value="{StaticResource ProgressBarTemplate}"/>
</Style>
<ControlTemplatex:Key="BusyIndicatorTemplate"TargetType="telerik:RadBusyIndicator">
<Grid>
<VisualStateManager.VisualStateGroups>
<VisualStateGroupx:Name="VisibilityStates">
<VisualStatex:Name="Hidden">
<Storyboard>
<ObjectAnimationUsingKeyFramesBeginTime="00:00:00"Duration="00:00:00.001"Storyboard.TargetProperty="(UIElement.Visibility)"Storyboard.TargetName="Overlay">
<DiscreteObjectKeyFrameKeyTime="00:00:00">
<DiscreteObjectKeyFrame.Value>
<Visibility>Collapsed</Visibility>
</DiscreteObjectKeyFrame.Value>
</DiscreteObjectKeyFrame>
</ObjectAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFramesStoryboard.TargetProperty="(UIElement.Visibility)"Storyboard.TargetName="shadow_A">
<DiscreteObjectKeyFrameKeyTime="0">
<DiscreteObjectKeyFrame.Value>
<Visibility>Collapsed</Visibility>
</DiscreteObjectKeyFrame.Value>
</DiscreteObjectKeyFrame>
</ObjectAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFramesStoryboard.TargetProperty="(UIElement.Visibility)"Storyboard.TargetName="ProgressBar">
<DiscreteObjectKeyFrameKeyTime="0">
<DiscreteObjectKeyFrame.Value>
<Visibility>Collapsed</Visibility>
</DiscreteObjectKeyFrame.Value>
</DiscreteObjectKeyFrame>
</ObjectAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFramesStoryboard.TargetProperty="(UIElement.Visibility)"Storyboard.TargetName="contentPresenter">
<DiscreteObjectKeyFrameKeyTime="0">
<DiscreteObjectKeyFrame.Value>
<Visibility>Collapsed</Visibility>
</DiscreteObjectKeyFrame.Value>
</DiscreteObjectKeyFrame>
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
<VisualStatex:Name="Visible">
<Storyboard>
<ObjectAnimationUsingKeyFramesBeginTime="00:00:00"Duration="00:00:00.001"Storyboard.TargetProperty="(UIElement.Visibility)"Storyboard.TargetName="Overlay">
<DiscreteObjectKeyFrameKeyTime="00:00:00">
<DiscreteObjectKeyFrame.Value>
<Visibility>Visible</Visibility>
</DiscreteObjectKeyFrame.Value>
</DiscreteObjectKeyFrame>
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
</VisualStateGroup>
<VisualStateGroupx:Name="BusyStatusStates">
<VisualStatex:Name="Idle">
<Storyboard>
<ObjectAnimationUsingKeyFramesBeginTime="00:00:00"Duration="00:00:00.001"Storyboard.TargetProperty="(Control.IsEnabled)"Storyboard.TargetName="Content">
<DiscreteObjectKeyFrameKeyTime="00:00:00">
<DiscreteObjectKeyFrame.Value>
<System:Boolean>True</System:Boolean>
</DiscreteObjectKeyFrame.Value>
</DiscreteObjectKeyFrame>
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
<VisualStatex:Name="Busy">
<Storyboard>
<ObjectAnimationUsingKeyFramesBeginTime="00:00:00"Duration="00:00:00.001"Storyboard.TargetProperty="(Control.IsEnabled)"Storyboard.TargetName="Content">
<DiscreteObjectKeyFrameKeyTime="00:00:00">
<DiscreteObjectKeyFrame.Value>
<System:Boolean>False</System:Boolean>
</DiscreteObjectKeyFrame.Value>
</DiscreteObjectKeyFrame>
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
</VisualStateGroup>
</VisualStateManager.VisualStateGroups>
<ContentControlx:Name="Content"ContentTemplate="{TemplateBinding ContentTemplate}"Content="{TemplateBinding Content}"HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}"IsEnabled="False"VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}"/>
<Rectanglex:Name="Overlay"Style="{TemplateBinding OverlayStyle}"Fill="WhiteSmoke"/>
<Rectanglex:Name="shadow_A"Height="10"VerticalAlignment="Top"StrokeThickness="0"Margin="0,0,0,0">
<Rectangle.OpacityMask>
<LinearGradientBrushEndPoint="1,0.5"StartPoint="0,0.5">
<GradientStopColor="White"Offset="0.5"/>
<GradientStopColor="#4C000000"/>
<GradientStopColor="#4C000000"Offset="1"/>
</LinearGradientBrush>
</Rectangle.OpacityMask>
<Rectangle.Fill>
<LinearGradientBrushEndPoint="0.5,1"StartPoint="0.5,0">
<GradientStopColor="#66000000"Offset="0"/>
<GradientStopOffset="0.7"/>
</LinearGradientBrush>
</Rectangle.Fill>
</Rectangle>
<telerik:RadProgressBarx:Name="ProgressBar"IsIndeterminate="{TemplateBinding IsIndeterminate}"Value="{TemplateBinding ProgressValue}"VerticalAlignment="Top"Style="{StaticResource ProgressBarStyle}"BorderThickness="0"Margin="0,-9,0,0">
<telerik:RadProgressBar.Foreground>
<LinearGradientBrushEndPoint="0.5,1"StartPoint="0.5,0">
<GradientStopColor="#FF2CB2FB"Offset="1"/>
<GradientStopColor="#FF137CB5"Offset="0"/>
</LinearGradientBrush>
</telerik:RadProgressBar.Foreground>
</telerik:RadProgressBar>
<ContentPresenterx:Name="contentPresenter"Content="{TemplateBinding BusyContent}"ContentTemplate="{TemplateBinding BusyContentTemplate}"HorizontalAlignment="Center"VerticalAlignment="Center"/>
</Grid>
</ControlTemplate>
<Stylex:Key="BusyIndicatorStyle"TargetType="telerik:RadBusyIndicator">
<SetterProperty="BusyContent"Value="Loading..."/>
<SetterProperty="IsTabStop"Value="False"/>
<SetterProperty="DisplayAfter"Value="0"/>
<SetterProperty="BorderThickness"Value="1"/>
<SetterProperty="HorizontalContentAlignment"Value="Stretch"/>
<SetterProperty="VerticalContentAlignment"Value="Stretch"/>
<SetterProperty="Template"Value="{StaticResource BusyIndicatorTemplate}"/>
</Style>
I hope this helps.