What causes "SR.SavedContextSchemaContextNull" in dotnet/wpf?

Ensure the XamlSavedContext was created with a non-null XamlSchemaContext before passing it to the XamlObjectWriter constructor.

dotnet/wpf · error · ArgumentException

SR.SavedContextSchemaContextNull

Error message

SR.SavedContextSchemaContextNull

What it means

ArgumentException thrown by the internal XamlObjectWriter(XamlSavedContext, XamlObjectWriterSettings) constructor when the supplied XamlSavedContext has a null SchemaContext. An XamlObjectWriter cannot function without a XamlSchemaContext, so the library rejects the saved context up front.

Solutions

Ensure the XamlSavedContext was created with a non-null XamlSchemaContext before passing it to the XamlObjectWriter constructor.
Re-create the saved context from a reader initialized with a valid XamlSchemaContext (e.g. new XamlSchemaContext()).
If the context comes from another component, assert/validate savedContext.SchemaContext != null before constructing the writer.

Example fix

// before
var writer = new XamlObjectWriter(savedContext, settings); // savedContext.SchemaContext == null
// after
if (savedContext.SchemaContext == null)
    throw new InvalidOperationException("Saved context has no schema context; recreate it from a reader with a XamlSchemaContext.");
var writer = new XamlObjectWriter(savedContext, settings);

Defensive patterns

Strategy: validation

Validate before calling

if (savedContext == null || savedContext.SchemaContext == null)
    throw new InvalidOperationException("savedContext requires a non-null SchemaContext.");

Type guard

static bool HasSchemaContext(XamlSavedContext c) => c?.SchemaContext != null;

Try / catch

try { new XamlObjectWriter(savedContext, settings); }
catch (ArgumentException ex) when (ex.ParamName == "savedContext") { RecreateContextAndRetry(); }

Prevention

Always construct XamlSavedContext from a reader initialized with a real XamlSchemaContext.
Validate savedContext.SchemaContext before constructing the writer.
Avoid persisting/transporting saved contexts without their schema context.
Keep reader and writer construction in one pipeline component so context is never dropped.

When it happens

Trigger: Passing a XamlSavedContext whose SchemaContext property is null to the internal XamlObjectWriter constructor — typically from a custom XamlReader pipeline that built the saved context without a schema context.

Common situations: Reusing a saved context captured from a partially-constructed or default-initialized reader; deserializing/persisting XAML state across AppDomains where the schema context was dropped; custom reader implementations that forget to pass the schema context through.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/899a574602fe92df. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/System.Xaml/System/Xaml/InfosetObjects/XamlObjectWriter.cs:62

        public XamlObjectWriter(XamlSchemaContext schemaContext)
        {
            ArgumentNullException.ThrowIfNull(schemaContext);
            Initialize(schemaContext, (XamlSavedContext)null, (XamlObjectWriterSettings)null);
        }

        public XamlObjectWriter(XamlSchemaContext schemaContext, XamlObjectWriterSettings settings)
        {
            ArgumentNullException.ThrowIfNull(schemaContext);
            Initialize(schemaContext, (XamlSavedContext)null, settings);
        }

        internal XamlObjectWriter(XamlSavedContext savedContext, XamlObjectWriterSettings settings)
        {
            ArgumentNullException.ThrowIfNull(savedContext);
            if (savedContext.SchemaContext is null)
            {
                throw new ArgumentException(SR.SavedContextSchemaContextNull, nameof(savedContext));
            }

            Initialize(savedContext.SchemaContext, savedContext, settings);
        }

        private void Initialize(XamlSchemaContext schemaContext, XamlSavedContext savedContext, XamlObjectWriterSettings settings)
        {
            _inDispose = false;
            // ObjectWriter must be passed in a non-null SchemaContext.  We check that here, since the CreateContext method
            // will create one if a null SchemaContext was passed in.
            ArgumentNullException.ThrowIfNull(schemaContext);
            if (savedContext is not null && schemaContext != savedContext.SchemaContext)
            {
                throw new ArgumentException(SR.SavedContextSchemaContextMismatch, nameof(schemaContext));
            }

            if (settings is not null)
            {

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