stride3d/stride · error · InvalidOperationException

A part named 'PART_TrimmedText' must be present in the Contr

Error message

A part named 'PART_TrimmedText' must be present in the ControlTemplate, and must be of type 'TextBlock'.

What it means

The Stride TextBox custom control requires its ControlTemplate to contain a named part 'PART_TrimmedText' of type TextBlock, used to render a trimmed/ellipsis version of the text. During OnApplyTemplate the control looks this part up via GetTemplateChild; if the template omits it or provides a different element type, the cast yields null and the control throws InvalidOperationException. This enforces the WPF template-part contract so the control's visual logic always has the elements it depends on.

Solutions

1. Add <TextBlock x:Name="PART_TrimmedText"/> to the custom ControlTemplate.
2. Ensure the element named PART_TrimmedText is a TextBlock, not another element type.
3. If not customizing visuals, remove the custom Style so the library's default template is used.

Example fix

// before (custom template missing part)
<Style TargetType="controls:TextBox">
  <Setter Property="Template">
    <Setter.Value>
      <ControlTemplate TargetType="controls:TextBox">
        <Border><ScrollViewer x:Name="PART_ContentHost"/></Border>
      </ControlTemplate>
    </Setter.Value>
  </Setter>
</Style>
// after
<ControlTemplate TargetType="controls:TextBox">
  <Border>
    <ScrollViewer x:Name="PART_ContentHost"/>
    <TextBlock x:Name="PART_TrimmedText" TextTrimming="CharacterEllipsis"/>
  </Border>
</ControlTemplate>

// In template resource review, assert required parts exist before applying:
var tb = template.FindName("PART_TrimmedText", templatedParentScope) as TextBlock;
if (tb == null) throw new InvalidOperationException("Template must contain TextBlock named PART_TrimmedText");

bool HasTrimmedTextPart(ControlTemplate t, FrameworkElement scope) =>
    scope != null && scope.FindName("PART_TrimmedText", scope) is TextBlock;

try { element.ApplyTemplate(); } catch (InvalidOperationException ex) when (ex.Message.Contains("PART_TrimmedText")) { /* restore default template or log template contract violation */ }

When it happens

Trigger: Applying a custom ControlTemplate to this TextBox control that lacks an element named 'PART_TrimmedText', or names it but the element is not a TextBlock (e.g. a Border or ContentPresenter). Also triggered when the default template resource fails to load so OnApplyTemplate runs against an empty/partial template.

Common situations: Developers restyling the control with a new Style/ControlTemplate and forgetting to copy required named parts; renaming the part in a copied template; theming resources missing after a library upgrade.

Understand the failure class

Background: Schema validation failed / invalid input schema: payload rejected because its shape doesn't match the expected schema — this error's family across 28 libraries.

Related errors

• A part named '{GridPartName}' must be present in the Control
• A part named 'PART_EditableTextBox' must be present in the C
• A part named 'PART_ListBox' must be present in the ControlTe
• A part named 'PART_LogTextBox' must be present in the Contro
• A part named 'PART_LogGridView' must be present in the Contr

AI-assisted analysis of stride3d/stride@96fad776d2 (2026-09-14). Data as JSON: /api/errors/f1ef5f6e66e63e60. Report an issue: GitHub.

Appendix: source

Thrown at sources/presentation/Stride.Core.Presentation.Wpf/Controls/TextBox.cs:85

        /// Gets or sets the amount of time before a validation of input text happens, in milliseconds.
        /// Every change to the <see cref="TextBox.Text"/> property reset the timer to this value.
        /// </summary>
        /// <remarks>The default value is <c>500</c> milliseconds.</remarks>
        public int ValidationDelay { get { return (int)GetValue(ValidationDelayProperty); } set { SetValue(ValidationDelayProperty, value); } }
        
        /// <summary>
        /// Gets the trimmed text to display when the control does not have the focus, depending of the value of the <see cref="TextTrimming"/> property.
        /// </summary>
        public string TrimmedText { get { return (string)GetValue(TrimmedTextPropertyKey.DependencyProperty); } private set { SetValue(TrimmedTextPropertyKey, value); } }

        /// <inheritdoc/>
        public override void OnApplyTemplate()
        {
            base.OnApplyTemplate();

            trimmedTextBlock = GetTemplateChild("PART_TrimmedText") as TextBlock;
            if (trimmedTextBlock == null)
                throw new InvalidOperationException("A part named 'PART_TrimmedText' must be present in the ControlTemplate, and must be of type 'TextBlock'.");
        }

        /// <summary>
        /// Raised when the text of the TextBox changes.
        /// </summary>
        /// <param name="oldValue">The old value of the <see cref="TextBox.Text"/> property.</param>
        /// <param name="newValue">The new value of the <see cref="TextBox.Text"/> property.</param>
        protected override void OnTextChanged(string oldValue, string newValue)
        {
            if (UseTimedValidation)
            {
                if (ValidationDelay > 0.0)
                {
                    validationTimer?.Change(ValidationDelay, Timeout.Infinite);
                }
                else
                {
                    Validate();

View on GitHub (pinned to 96fad776d2)