Performance with WPF Combo Box inside a ListView <p>I was wondering if I was missing something obvious.</p> <p>I have a simple window with a ListView with 3 columns in it. One displays text and the other two have combo boxes in them.</p> <p>The ListView has approx. 500 records and the Comboboxes both pull from the same contact list which has approx. 8,000 records in it.</p> <p>I am using MVVM.</p> <p>This window takes for ever to open and once it does open it is practically frozen solid (it moves so slow)</p> <p>the queries to the database take under ten seconds (I log when the VM is fully loaded) then it takes two or three minutes to open the window. I made sure to store both lists in <code>List&lt;T&gt;</code> in my VM to make sure its not reprocessing the data or anything like that.</p> <p>As you can see below. I've tried explicitly using Virtualizing Stack Panel but that did not help much.</p> <p>Thank you for any help</p> <pre><code> &lt;DataTemplate x:Key="ComboboxItemTemplate"&gt; &lt;Grid&gt; &lt;Grid.ColumnDefinitions&gt; &lt;ColumnDefinition Width="Auto" /&gt; &lt;ColumnDefinition Width="*" /&gt; &lt;/Grid.ColumnDefinitions&gt; &lt;Grid.RowDefinitions&gt; &lt;RowDefinition Height="Auto" /&gt; &lt;RowDefinition Height="Auto" /&gt; &lt;RowDefinition Height="Auto" /&gt; &lt;/Grid.RowDefinitions&gt; &lt;Image Grid.RowSpan="3" Source="{Binding ImageURL, IsAsync=True}" Width="50" /&gt; &lt;TextBlock Grid.Column="1" Text="{Binding Name}" /&gt; &lt;TextBlock Grid.Column="1" Grid.Row="1" Text="{Binding Email}" /&gt; &lt;TextBlock Grid.Column="1" Grid.Row="2" Text="{Binding CampusName}" /&gt; &lt;/Grid&gt; &lt;/DataTemplate&gt; &lt;ListView ItemsSource="{Binding MainList}" IsSynchronizedWithCurrentItem="True" Grid.RowSpan="2"&gt; &lt;ListView.ItemsPanel&gt; &lt;ItemsPanelTemplate&gt; &lt;VirtualizingStackPanel /&gt; &lt;/ItemsPanelTemplate&gt; &lt;/ListView.ItemsPanel&gt; &lt;ListView.View&gt; &lt;GridView&gt; &lt;GridViewColumn Width="200" Header="Internal"&gt; &lt;GridViewColumn.CellTemplate&gt; &lt;DataTemplate&gt; &lt;StackPanel&gt; &lt;TextBlock Text="{Binding Name}" FontWeight="Bold" /&gt; &lt;TextBlock Text="{Binding MName}" /&gt; &lt;TextBlock Text="{Binding CampusName}" /&gt; &lt;/StackPanel&gt; &lt;/DataTemplate&gt; &lt;/GridViewColumn.CellTemplate&gt; &lt;/GridViewColumn&gt; &lt;GridViewColumn Width="200" Header="Contact1"&gt; &lt;GridViewColumn.CellTemplate&gt; &lt;DataTemplate&gt; &lt;ComboBox ItemsSource="{Binding Source={StaticResource VM}, Path=ContactList, IsAsync=True}" SelectedValue="{Binding HisContactID}" SelectedValuePath="id" ItemTemplate="{StaticResource ComboboxItemTemplate}" Background="{Binding HisColor}" Margin="0,82,0,115" Grid.Row="1" Grid.Column="1"&gt; &lt;ComboBox.ItemsPanel&gt; &lt;ItemsPanelTemplate&gt; &lt;VirtualizingStackPanel /&gt; &lt;/ItemsPanelTemplate&gt; &lt;/ComboBox.ItemsPanel&gt; &lt;/ComboBox&gt; &lt;/DataTemplate&gt; &lt;/GridViewColumn.CellTemplate&gt; &lt;/GridViewColumn&gt; &lt;GridViewColumn Width="200" Header="Contact2"&gt; ... &lt;/GridViewColumn&gt; &lt;/GridView&gt; &lt;/ListView.View&gt; &lt;/ListView&gt; </code></pre>