dotnet/wpf · error · InvalidOperationException

SR.Format(SR.TextSchema_TextIsNotAllowed…

Error message

SR.Format(SR.TextSchema_TextIsNotAllowed, this.GetType().Name)

What it means

TextElement.AddText throws InvalidOperationException when text content is not permitted under this element's schema and the supplied string is not pure whitespace. Non-whitespace text is rejected with TextSchema_TextIsNotAllowed naming the element type; whitespace-only text is silently ignored.

Solutions

Wrap the text in a Run inside a schema-valid text container (e.g. Paragraph).
Remove the AddText call for elements that don't accept text.
Strip/ignore the text if only whitespace.

Example fix

// before
table.AddText("Hello");
// after
var p = new Paragraph(new Run("Hello"));
flowDocument.Blocks.Add(p);

Defensive patterns

Strategy: validation

Validate before calling

bool textAllowed = element is Run || element is Paragraph || element is Span;
if (!textAllowed && text.Trim().Length > 0) throw new InvalidOperationException("Wrap text in a Run inside a Paragraph");

Try / catch

try { element.AddText(text); }
catch (InvalidOperationException) { var p = new Paragraph(new Run(text)); flowDocument.Blocks.Add(p); }

Prevention

Only AddText on text-accepting elements
Ignore whitespace-only strings for non-text elements
Wrap raw strings in Run before insertion

When it happens

Trigger: Calling AddText (or XAML text content under an element) where the element's schema disallows text, e.g. AddText on a Table, Section, or UIContainer with non-whitespace string.

Common situations: XAML putting stray text inside container elements; code building documents that appends text to non-text-holding elements.

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

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/e5e28ab0847ab6e2. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Documents/TextElement.cs:883

            else
            {
                // Implicit Run creation
                if (TextSchema.IsValidChild(/*parent:*/this, /*childType:*/typeof(Run)))
                {
                    // NOTE: Do not use new Run(text) constructor to avoid TextContainer creation
                    // which would hit parser perf
                    Run implicitRun = Inline.CreateImplicitRun(this);

                    Append(implicitRun);

                    implicitRun.Text = text;
                }
                else
                {
                    // Otherwise text is not allowed. Throw if it is not a whitespace
                    if (text.Trim().Length > 0)
                    {
                        throw new InvalidOperationException(SR.Format(SR.TextSchema_TextIsNotAllowed, this.GetType().Name));
                    }

                    // As to whitespace - it can be simply ignored
                }
            }
        }

        #endregion IAddChild

        #region LogicalTree

        /// <summary>
        /// Returns enumerator to logical children.
        /// </summary>
        protected internal override IEnumerator LogicalChildren
        {
            get
            {

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