Step-by-Step: Building a High-Performance Master-Detail Grid in WPF (MVVM, Async Loads)

Master–detail UIs are notorious performance traps in WPF. Expanding details multiplies the visual tree, tanks frame rate, and wrecks smooth scrolling. This guide shows how to keep it snappy with MVVM-driven state, async commands, and aggressive virtualization inside a WPF DataGrid.

Introduction

Master–detail UIs are notorious for slowing WPF applications down. Expanding detail rows often multiplies the visual tree, killing performance and scroll fluidity. This guide shows how to keep things snappy by combining MVVM, async commands, and virtualization inside a WPF DataGrid.

What You’ll Build

Master grid of Orders
On expand → details load asynchronously (Items per Order)
Smooth scrolling with row virtualization and recycling

Key XAML (trimmed for clarity)

<DataGrid ItemsSource="{Binding Orders}"
          EnableRowVirtualization="True"
          VirtualizingPanel.IsVirtualizing="True"
          VirtualizingPanel.VirtualizationMode="Recycling">

  <DataGrid.RowDetailsTemplate>
    <DataTemplate>
      <ItemsControl ItemsSource="{Binding Items}" />
    </DataTemplate>
  </DataGrid.RowDetailsTemplate>
</DataGrid>

Virtualization flags keep scrolling smooth.
RowDetailsTemplate bound to a lightweight Items view.
Async command loads details without blocking UI.

MVVM Pattern

ViewModel exposes ObservableCollection<OrderVm>.
Each OrderVm loads details with a Task-based async method.
Placeholder UI shown instantly while data fetch runs.
Cancellation tokens ensure stale loads are canceled during rapid navigation.

Performance Tips

Keep detail templates lightweight (avoid heavy converters).
Defer expensive bindings until IsVisible == true.
Cache small detail views if reused frequently.

Developer Wins

Users perceive instant expand response.
No UI thread stalls during slow I/O.
Clean MVVM separation → easier testing and maintenance.

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FAQ

Q: Can I prefetch details for the next rows?

A: Yes. Prefetch adjacent rows on scroll idle, but keep requests cancellable.

Q: Will virtualization break details?

A: No. Details render on demand. Just keep templates lightweight.

Q: How do I theme the details consistently?

A: Apply Toolkit Plus themes or shared resource dictionaries.