WPF chart heavy cpu usage on update itemsource - wpf

Question

First of all i want to apologize, because i don't know how to ask the question the right way.
I'm not sure how to describe the problem i have.
There is a page in my wpf-application where i draw some lineseries on a chart.
<Page x:Class="Zentralvakuum_Archivauswertung.Views.Zentrale"
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:Zentralvakuum_Archivauswertung.Views"
xmlns:DV="clr-namespace:System.Windows.Controls.DataVisualization;assembly=System.Windows.Controls.DataVisualization.Toolkit"
xmlns:DVC="clr-namespace:System.Windows.Controls.DataVisualization.Charting;assembly=System.Windows.Controls.DataVisualization.Toolkit"
xmlns:xctk="http://schemas.xceed.com/wpf/xaml/toolkit"
mc:Ignorable="d"
DataContext="{Binding Source={StaticResource ViewModelLocator}, Path=ZentraleVm}"
d:DesignHeight="300" d:DesignWidth="300"
Title="Zentrale">
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="*"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<DVC:Chart Name="Chart" Width="auto" Height="auto" Title="Something" grid.row="0">
<DVC:Chart.Series>
<DVC:LineSeries Title="1"
IndependentValueBinding="{Binding Path=Key}"
DependentValueBinding="{Binding Path=Value}" ItemsSource="{Binding Istwerte1Liste, UpdateSourceTrigger=PropertyChanged}" >
<DVC:LineSeries.DataPointStyle>
<Style TargetType="DVC:LineDataPoint">
<Setter Property="Template" Value="{x:Null}" />
<Setter Property="Background" Value="Black"/>
<Setter Property="Opacity" Value="0" />
</Style>
</DVC:LineSeries.DataPointStyle>
</DVC:LineSeries>
<DVC:LineSeries Title="1a"
IndependentValueBinding="{Binding Path=Key}"
DependentValueBinding="{Binding Path=Value}" ItemsSource="{Binding Sollwerte1Liste, UpdateSourceTrigger=PropertyChanged}">
<DVC:LineSeries.DataPointStyle>
<Style TargetType="DVC:LineDataPoint">
<Setter Property="Template" Value="{x:Null}" />
<Setter Property="Background" Value="Green"/>
<Setter Property="Opacity" Value="0" />
</Style>
</DVC:LineSeries.DataPointStyle>
</DVC:LineSeries>
<DVC:LineSeries Title="2"
IndependentValueBinding="{Binding Path=Key}"
DependentValueBinding="{Binding Path=Value}" ItemsSource="{Binding Istwerte2Liste, UpdateSourceTrigger=PropertyChanged}" >
<DVC:LineSeries.DataPointStyle>
<Style TargetType="DVC:LineDataPoint">
<Setter Property="Template" Value="{x:Null}" />
<Setter Property="Background" Value="Blue"/>
<Setter Property="Opacity" Value="0" />
</Style>
</DVC:LineSeries.DataPointStyle>
</DVC:LineSeries>
<DVC:LineSeries Title="2a"
IndependentValueBinding="{Binding Path=Key}"
DependentValueBinding="{Binding Path=Value}" ItemsSource="{Binding Sollwerte2Liste, UpdateSourceTrigger=PropertyChanged}">
<DVC:LineSeries.DataPointStyle>
<Style TargetType="DVC:LineDataPoint">
<Setter Property="Template" Value="{x:Null}" />
<Setter Property="Background" Value="Red"/>
<Setter Property="Opacity" Value="0" />
</Style>
</DVC:LineSeries.DataPointStyle>
</DVC:LineSeries>
</DVC:Chart.Series>
</DVC:Chart>
<Grid Grid.Row="1">
<Grid.ColumnDefinitions>
<ColumnDefinition/>
<ColumnDefinition/>
</Grid.ColumnDefinitions>
<StackPanel Grid.Column="0" HorizontalAlignment="Center">
<Label DockPanel.Dock="Top" HorizontalAlignment="Center" FontWeight="Bold" FontSize="20" Content="Start:"/>
<xctk:DateTimePicker Value="{Binding Start, UpdateSourceTrigger=PropertyChanged}" Format="FullDateTime" ShowDropDownButton="False" HorizontalContentAlignment="Center"/>
<Button Content="Actualize" Command="{Binding ActualizeCommand}"/>
</StackPanel>
<StackPanel Grid.Column="1" HorizontalAlignment="Center">
<Label DockPanel.Dock="Top" HorizontalAlignment="Center" FontWeight="Bold" FontSize="20" Content="Ende:"/>
<xctk:DateTimePicker Value="{Binding End, UpdateSourceTrigger=PropertyChanged}" Format="FullDateTime" ShowDropDownButton="False" HorizontalContentAlignment="Center"/>
<Button Content="Actualize" Command="{Binding ActualizeCommand}"/>
</StackPanel>
</Grid>
</Grid>
The first time these page is opened everything goes fine, page opens, lineseries are drawn and done.
When i update the itemsources of the lineseries, lineseries are drawn and ... applicationfreeze for a long time caused of heavy cpu usage. I linked an image of this.
green square = frist opening of the page, red square = update of itemsource (green bar = chart updated, all my code is done)
Following the update funtion:
public void Actualize()
{
WerteZentrale = null;
WerteZentraleCollection = null;
//Get values from db
WerteZentrale = new Vakuumverlauf_ZentraleEntities1();
WerteZentraleCollection = new ListCollectionView((from a in WerteZentrale.Werte_Zentrale0 where a.TimeString != string.Empty select a).ToList());
//filter
WerteZentraleCollection.Filter = (found) =>
{
Werte_Zentrale0 a = found as Werte_Zentrale0;
return (Convert.ToDateTime(a.TimeString) >= Start && Convert.ToDateTime(a.TimeString) <= Ende);
};
//sort
WerteZentraleCollection.CustomSort = new DateTimeComparerWerte();
//empty observablecollections
Istwerte1ListeDummy.Clear();
Sollwerte1ListeDummy.Clear();
Istwerte2ListeDummy.Clear();
Sollwerte2ListeDummy.Clear();
Istwerte1Liste.Clear();
Sollwerte1Liste.Clear();
Istwerte2Liste.Clear();
Sollwerte2Liste.Clear();
foreach (Werte_Zentrale0 Wert in WerteZentraleCollection)
{
//1
if (Wert.VarName == "VakuumWerte_VK1_Istwert_Istwert")
{
Istwerte1ListeDummy.Add(new KeyValuePair<DateTime, double?>(Convert.ToDateTime(Wert.TimeString), Wert.VarValue));
}
//1a
if (Wert.VarName == "VakuumWerte_VK1_Sollwert")
{
Sollwerte1ListeDummy.Add(new KeyValuePair<DateTime, double?>(Convert.ToDateTime(Wert.TimeString), Wert.VarValue));
}
//2
if (Wert.VarName == "VakuumWerte_VK2_Istwert_Istwert")
{
Istwerte2ListeDummy.Add(new KeyValuePair<DateTime, double?>(Convert.ToDateTime(Wert.TimeString), Wert.VarValue));
}
//2a
if (Wert.VarName == "VakuumWerte_VK2_Sollwert")
{
Sollwerte2ListeDummy.Add(new KeyValuePair<DateTime, double?>(Convert.ToDateTime(Wert.TimeString), Wert.VarValue));
}
}
//write to itemsource
Istwerte1Liste = Istwerte1ListeDummy;
Sollwerte1Liste = Sollwerte1ListeDummy;
Istwerte2Liste = Istwerte2ListeDummy;
Sollwerte2Liste = Sollwerte2ListeDummy;
}
This function is called in the constructor of the viewmodel, aswell as at the ActualizeCommand.
So for me, i'm doing the same thing in both cases but something different is the result and i have no clue why.