dotnet/wpf · error · InvalidOperationException

SR.Format(SR.StyleForWrongType, style.TargetType.Name…

Error message

SR.Format(SR.StyleForWrongType, style.TargetType.Name, container.GetType().Name)

What it means

When the ItemsControl generates a container (e.g. ListBoxItem) it applies the resolved ItemContainerStyle only if style.TargetType is instance-compatible with the container (style.TargetType.IsInstanceOfType(container)). A style whose TargetType does not match the actual container type is rejected with an InvalidOperationException naming both types.

Solutions

Change the style's TargetType to the actual container type (e.g. ListBoxItem for ListBox).
Remove TargetType from the style if it is shared across container types and the setters do not require it.
Ensure the ItemContainerStyle is assigned to the matching control type.

Example fix

// before
<ListBox>
  <ListBox.ItemContainerStyle>
    <Style TargetType="ListViewItem"><Setter Property="HorizontalContentAlignment" Value="Stretch"/></Style>
  </ListBox.ItemContainerStyle>
</ListBox>
// after
<ListBox>
  <ListBox.ItemContainerStyle>
    <Style TargetType="ListBoxItem"><Setter Property="HorizontalContentAlignment" Value="Stretch"/></Style>
  </ListBox.ItemContainerStyle>
</ListBox>

Defensive patterns

Strategy: type-guard

Validate before calling

bool IsContainerStyleCompatible(Style style, FrameworkElement container) =>
    style == null || style.TargetType == null || style.TargetType.IsInstanceOfType(container);

Type guard

bool IsStyleFor<TContainer>(Style style) where TContainer : class => style?.TargetType?.IsAssignableFrom(typeof(TContainer)) == true;

Try / catch

try { itemsControl.ItemContainerStyle = style; } catch (InvalidOperationException ex) when (ex.Message.Contains("TargetType")) { /* assign a style with corrected TargetType */ }

Prevention

Match the style TargetType to the container type the control actually generates (ListBoxItem, ListViewItem, TreeViewItem, ComboBoxItem).
Use x:Type with the exact container type; verify when refactoring control types.
Do not share one container style across control families without checking TargetType.

When it happens

Trigger: Setting ItemContainerStyle (or a style resolved for the container) with TargetType e.g. ListViewItem on a ListBox (whose containers are ListBoxItem), or a TargetType mismatch after changing the control type; also reusing one container style across different ItemsControl types.

Common situations: Copying container styles between ListBox and ListView (ListBoxItem vs ListViewItem); refactoring the control type without updating ItemContainerStyle TargetType; implicit styles keyed to the wrong container type.

Understand the failure class

Background: Type mismatch errors: IllegalArgumentException, TypeError and type guards across 150 open-source libraries — this error's family across 150 libraries.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/d8a1b1fc8643b9af. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Controls/ItemsControl.cs:3477

            // Control's ItemContainerStyle has first stab
            Style style = ItemContainerStyle;

            // no ItemContainerStyle set, try ItemContainerStyleSelector
            if (style == null)
            {
                if (ItemContainerStyleSelector != null)
                {
                    style = ItemContainerStyleSelector.SelectStyle(item, container);
                }
            }

            // apply the style, if found
            if (style != null)
            {
                // verify style is appropriate before applying it
                if (!style.TargetType.IsInstanceOfType(container))
                    throw new InvalidOperationException(SR.Format(SR.StyleForWrongType, style.TargetType.Name, container.GetType().Name));

                foContainer.Style = style;
                foContainer.IsStyleSetFromGenerator = true;
            }
            else if (foContainer.IsStyleSetFromGenerator)
            {
                // if Style was formerly set from ItemContainerStyle, clear it
                foContainer.IsStyleSetFromGenerator = false;
                container.ClearValue(FrameworkElement.StyleProperty);
            }
        }

        private void RemoveItemContainerStyle(DependencyObject container)
        {
            FrameworkObject foContainer = new FrameworkObject(container);

            if (foContainer.IsStyleSetFromGenerator)
            {

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