fixed some issues at design time

src/Shared/HandyControlDemo_Shared/UserControl/Main/OverView.xaml

@@ -343,13 +343,13 @@
                     </hc:Transfer.ItemTemplate>
                 </hc:Transfer>
             </Border>
-            <Border Visibility="Collapsed" BorderThickness="0" Padding="16" Style="{StaticResource BorderRegion}" CornerRadius="4" Canvas.Left="611" Canvas.Top="976">
+            <Border Visibility="Visible" BorderThickness="0" Padding="16" Style="{StaticResource BorderRegion}" CornerRadius="4" Canvas.Left="611" Canvas.Top="976">
                 <userControl:CoverFlowDemoCtl Width="563" Margin="-32" Background="Transparent"/>
             </Border>
-            <Border Visibility="Collapsed" BorderThickness="0" Padding="16" Style="{StaticResource BorderRegion}" CornerRadius="4" Canvas.Left="1391" Canvas.Top="648" Width="274">
+            <Border Visibility="Visible" BorderThickness="0" Padding="16" Style="{StaticResource BorderRegion}" CornerRadius="4" Canvas.Left="1391" Canvas.Top="648" Width="274">
                 <userControl:ColorPickerDemoCtl Margin="-32" Background="Transparent"/>
             </Border>
-            <Border Visibility="Collapsed" BorderThickness="0" Padding="16" Style="{StaticResource BorderRegion}" CornerRadius="4" Canvas.Left="1113" Canvas.Top="608" Width="264" Height="126">
+            <Border Visibility="Visible" BorderThickness="0" Padding="16" Style="{StaticResource BorderRegion}" CornerRadius="4" Canvas.Left="1113" Canvas.Top="608" Width="264" Height="126">
                 <hc:TagPanel Orientation="Horizontal" MaxWidth="400" VerticalAlignment="Center">
                     <hc:Tag ShowCloseButton="False" Content="TextText"/>
                     <hc:Tag Content="Text"/>

src/Shared/HandyControl_Shared/Controls/ColorPicker/ColorPicker.cs

@@ -478,7 +478,7 @@ namespace HandyControl.Controls
         /// </summary>
         private void UpdateStatus(Color color)
         {
-            if (_isOnDragging) return;
+            if (_isOnDragging || _sliderColor == null) return;
 
             var r = color.R;
             var g = color.G;

src/Shared/HandyControl_Shared/Controls/Cover/CoverFlow/CoverFlow.cs

@@ -204,7 +204,7 @@ namespace HandyControl.Controls
         /// <param name="pos"></param>
         private void Remove(int pos)
         {
-            var item = _itemShowList[pos];
+            if (!_itemShowList.TryGetValue(pos, out var item)) return;
             _visualParent.Children.Remove(item);
             _itemShowList.Remove(pos);
         }
@@ -308,10 +308,17 @@ namespace HandyControl.Controls
         {
             if (content is Uri uri)
             {
-                return new CoverFlowItem(index, PageIndex, new Image
+                try
                 {
-                    Source = BitmapFrame.Create(uri)
-                });
+                    return new CoverFlowItem(index, PageIndex, new Image
+                    {
+                        Source = BitmapFrame.Create(uri, BitmapCreateOptions.DelayCreation, BitmapCacheOption.OnDemand)
+                    });
+                }
+                catch
+                {
+                    return new CoverFlowItem(index, PageIndex, new ContentControl());
+                }
             }
 
             return new CoverFlowItem(index, PageIndex, new ContentControl

src/Shared/HandyControl_Shared/Controls/Other/Carousel.cs

@@ -61,7 +61,7 @@ namespace HandyControl.Controls
             _itemsControl = GetTemplateChild(ElementItemsControl) as ItemsPresenter;
             _panelPage = GetTemplateChild(ElementPanelPage) as Panel;
 
-            CheckNull();
+            if (!CheckNull()) return;
 
             _panelPage.AddHandler(ButtonBase.ClickEvent, new RoutedEventHandler(ButtonPages_OnClick));
             _appliedTemplate = true;
@@ -74,10 +74,7 @@ namespace HandyControl.Controls
             UpdatePageButtons(_pageIndex);
         }
 
-        private void CheckNull()
-        {
-            if (_itemsControl == null || _panelPage == null) throw new Exception();
-        }
+        private bool CheckNull() => !(_itemsControl == null || _panelPage == null);
 
         public static readonly DependencyProperty AutoRunProperty = DependencyProperty.Register(
             "AutoRun", typeof(bool), typeof(Carousel), new PropertyMetadata(ValueBoxes.FalseBox, (o, args) =>
@@ -195,6 +192,7 @@ namespace HandyControl.Controls
         /// </summary>
         public void UpdatePageButtons(int index = -1)
         {
+            if (!CheckNull()) return;
             if (!_appliedTemplate) return;
 
             var count = Items.Count;
@@ -236,6 +234,7 @@ namespace HandyControl.Controls
         /// </summary>
         private void UpdateItemsPosition()
         {
+            if (!CheckNull()) return;
             if (!_appliedTemplate) return;
             if (Items.Count == 0) return;
             if (!IsCenter)
@@ -284,6 +283,7 @@ namespace HandyControl.Controls
 
         private void ButtonPages_OnClick(object sender, RoutedEventArgs e)
         {
+            if (!CheckNull()) return;
             if (_selectedButton != null && _selectedButton.Content is Border borderOri)
                 borderOri.Background = Brushes.White;
             _selectedButton = e.OriginalSource as Button;

src/Shared/HandyControl_Shared/Controls/Time/TimeBar/TimeBar.cs

@@ -400,6 +400,7 @@ namespace HandyControl.Controls
 
         private void TimeBar_OnSizeChanged(object sender, SizeChangedEventArgs e)
         {
+            if (_canvasSpe == null) return;
             _speBlockList.Clear();
             _canvasSpe.Children.Clear();
 
@@ -442,7 +443,7 @@ namespace HandyControl.Controls
         {
             var p = Mouse.GetPosition(this);
             var mlliseconds = (p.X - ActualWidth / 2) / _itemWidth * _timeSpeList[_speIndex];
-            if (double.IsInfinity(mlliseconds)) return;
+            if (double.IsNaN(mlliseconds) || double.IsInfinity(mlliseconds)) return;
             _textBlockMove.Text = mlliseconds < 0
                 ? (SelectedTime - TimeSpan.FromMilliseconds(-mlliseconds)).ToString(TimeFormat)
                 : (SelectedTime + TimeSpan.FromMilliseconds(mlliseconds)).ToString(TimeFormat);

src/Shared/HandyControl_Shared/Themes/Styles/TransitioningContentControl.xaml

@@ -87,7 +87,7 @@
                                     </TransformGroup>
                                 </ContentPresenter.RenderTransform>
                             </ContentPresenter>
-                            <ContentPresenter x:Name="CurrentContentPresentationSite" Content="{x:Null}" ContentTemplate="{TemplateBinding ContentTemplate}" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}">
+                            <ContentPresenter x:Name="CurrentContentPresentationSite" ContentTemplate="{TemplateBinding ContentTemplate}" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}">
                                 <ContentPresenter.RenderTransform>
                                     <TransformGroup>
                                         <ScaleTransform />