Performance Delay When Dynamically Populating WPF ItemsControl with Multiple ContentControls

[PooraniSF4929]

Description

In a WPF application, we are experiencing a significant performance bottleneck when dynamically populating an ItemsControl with a large number of ContentControl elements. The control is configured with a horizontal StackPanel as its ItemsPanelTemplate, and we populate it programmatically using a loop that adds approximately 2000 ContentControl instances. This results in a noticeable delay in UI rendering. The delay scales with the number of items added. We expect the UI to render quickly and the items should be displayed in view once the add button is clicked without delay.

This issue is reproducible in a minimal setup. I have attached a simple sample project for your reference, which demonstrates the rendering delay when dynamically adding a large number of ContentControl elements nearly 2000 to an ItemsControl.

Simple sample - ItemsControl_Sample_WPF.zip

Reproduction Steps

1. Run the sample
2. Click the Add Items button to add 2000 content control instances
3. Observe the delay in UI rendering of the items.

Expected behavior

The UI should render the items quickly, even when adding a large number of lightweight visual elements.

Actual behavior

There is a noticeable delay in rendering 2000 items after the button click. The delay increases with the number of items added.

Delay_In_Displaying_Items_After_Add_Button_Clicked.mp4

Regression?

No response

Known Workarounds

No response

Impact

No response

Configuration

Other information

No response

[miloush]

Can you quantify "quickly"? Would 50ms be acceptable? Because that is how long it takes for me.

Either way, try VirtualizingStackPanel instead. With StackPanel, all the controls get created at once.

[harshit7962]

@PooraniSF4929 did VirtualizingStackPanel resolve the issue, and if so can we close this issue?

[PooraniSF4929]

We tried replacing the StackPanel with VirtualizingStackPanel in the ItemsPanelTemplate of our ItemsControl, and ensured that virtualization-related properties such as VirtualizingStackPanel.IsVirtualizing, VirtualizationMode, and ScrollViewer.CanContentScroll are properly set. However, we still did not observe any measurable improvement in rendering performance in our scenario.

Could you please confirm if this is the recommended approach to enable virtualization for ItemsControl when using ContentControl elements? If there are additional requirements or configurations needed to make virtualization effective in this context, we would appreciate your guidance.

If possible, could you share a modified version of the sample that demonstrates the recommended setup with improved performance using VirtualizingStackPanel? This would help us verify whether we have correctly implemented virtualization in this case.