stride3d/stride · error · InvalidOperationException

A part named 'PART_EditableTextBox' must be present in the…

Error message

A part named 'PART_EditableTextBox' must be present in the ControlTemplate, and must be of type 'Stride.Core.Presentation.Controls.Input.TextBox'.

What it means

FilteringComboBox.OnApplyTemplate fetches the mandatory template part 'PART_EditableTextBox' and requires it to be the library's Stride TextBox type, wiring text-change/key/event handlers onto it. A missing or wrong-type part makes the combo non-functional, so it throws InvalidOperationException. A second check for PART_ListBox follows.

Solutions

  1. Include an element named PART_EditableTextBox of type Stride.Core.Presentation.Controls.Input.TextBox in the ControlTemplate.
  2. Replace any System.Windows.Controls.TextBox used under that name with the Stride TextBox (it exposes TextChanged/Validating/Cancelled events).
  3. Restore the default template from the Stride theme dictionary and re-apply customizations.

Example fix

<!-- before -->
<TextBox x:Name="PART_EditableTextBox"/>
<!-- after -->
<presentation:TextBox x:Name="PART_EditableTextBox"
    xmlns:presentation="http://schemas.stride3d.net/xaml/presentation"/>
Defensive patterns

Strategy: validation

Validate before calling

var tb = combo.Template?.FindName("PART_EditableTextBox", combo);
if (tb is not Stride.Core.Presentation.Controls.Input.TextBox)
    throw new InvalidOperationException("Template needs a Stride TextBox named PART_EditableTextBox.");

Type guard

bool HasEditableTextBoxPart(FilteringComboBox combo) => combo.Template?.FindName("PART_EditableTextBox", combo) is Stride.Core.Presentation.Controls.Input.TextBox;

Try / catch

try { combo.ApplyTemplate(); }
catch (InvalidOperationException ex) { log.Error("FilteringComboBox template missing parts", ex); }

Prevention

When it happens

Trigger: Applying a ControlTemplate for FilteringComboBox that omits the element named PART_EditableTextBox, names it differently, or uses a plain System.Windows.Controls.TextBox instead of Stride's Stride.Core.Presentation.Controls.Input.TextBox.

Common situations: Re-templating FilteringComboBox from scratch; copying the default template but dropping or retyping the editable textbox part; theme resources missing so the default template isn't applied.

Understand the failure class

Background: 'Could not be found', 'does not exist', 'not found in database': the resource-not-found family when an ID, slug, key, or URI lookup comes back empty — this error's family across 20 libraries.

Related errors

AI-assisted analysis of stride3d/stride@96fad776d2 (2026-09-14). Data as JSON: /api/errors/278d2839814c3a13. Report an issue: GitHub.

Appendix: source

Thrown at sources/presentation/Stride.Core.Presentation.Wpf/Controls/FilteringComboBox.cs:240

            }
        }

        private static void OnIsFilteringChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            var filteringComboBox = (FilteringComboBox)d;
            if (filteringComboBox.ItemsSource != null)
            {
                filteringComboBox.UpdateCollectionView();
            }
        }

        public override void OnApplyTemplate()
        {
            base.OnApplyTemplate();

            editableTextBox = GetTemplateChild("PART_EditableTextBox") as TextBox;
            if (editableTextBox == null)
                throw new InvalidOperationException("A part named 'PART_EditableTextBox' must be present in the ControlTemplate, and must be of type 'Stride.Core.Presentation.Controls.Input.TextBox'.");

            listBox = GetTemplateChild("PART_ListBox") as ListBox;
            if (listBox == null)
                throw new InvalidOperationException("A part named 'PART_ListBox' must be present in the ControlTemplate, and must be of type 'ListBox'.");

            editableTextBox.TextChanged += EditableTextBoxTextChanged;
            editableTextBox.PreviewKeyDown += EditableTextBoxPreviewKeyDown;
            editableTextBox.Validating += EditableTextBoxValidating;
            editableTextBox.Validated += EditableTextBoxValidated;
            editableTextBox.Cancelled += EditableTextBoxCancelled;
            editableTextBox.LostFocus += EditableTextBoxLostFocus;
            listBox.MouseUp += ListBoxMouseUp;
        }

        protected override void OnGotKeyboardFocus(KeyboardFocusChangedEventArgs e)
        {
            base.OnGotKeyboardFocus(e);
            if (OpenDropDownOnFocus && !listBoxClicking)

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