dotnet/wpf · error · ArgumentException

The property 'propertyName' does not exist on type…

Error message

The property 'propertyName' does not exist on type 'sourceTypeName'.

What it means

PropertyMap throws this ArgumentException when a caller attempts to Translate, Apply, Add, or Reset a property name that does not exist on the wrapped Windows Forms SourceObject. PropertyMap only maps properties that the underlying WinForms control actually exposes; GetProperty(propertyName) returns null when the reflection lookup fails, so the map refuses to proceed rather than silently ignoring the request.

Solutions

1. Verify the property exists on the SourceObject's concrete type and fix the spelling/casing of the property name.
2. Check with propertyMap.SourceObject.GetType().GetProperty("<name>") before mapping.
3. Remove obsolete entries from the PropertyMap for properties that no longer exist on the control.
4. Ensure SourceObject is the type you expect (check SourceObject.GetType().FullName in the message).

Example fix

// before
propertyMap.Translate("Foreground", (o, e) => { ... }); // Foreground not on this control
// after
if (propertyMap.SourceObject.GetType().GetProperty("BackColor") != null)
{
    propertyMap.Translate("BackColor", (o, e) => { ... });
}

if (propertyMap.SourceObject == null || propertyMap.SourceObject.GetType().GetProperty(propertyName) == null)
    throw new InvalidOperationException($"Property '{propertyName}' does not exist on {propertyMap.SourceObject?.GetType().FullName}");

bool IsMappedProperty(PropertyMap map, string name) =>
    map.SourceObject?.GetType().GetProperty(name) != null;

try { propertyMap.Translate(name, value); }
catch (ArgumentException ex) { log.Warn($"Skipping unmapped property '{name}'", ex); }

When it happens

Trigger: Calling propertyMap.Translate("Foreground", value) or propertyMap.Apply() when 'Foreground' is not a property of SourceObject (e.g. mapping a WPF-style property name onto a control that lacks it); passing a misspelled property name; using PropertyMap on a System.Windows.Forms.Integration.WindowsFormsHost with a Child control whose property set differs from what was assumed.

Common situations: Copy-pasting PropertyMap setup code between controls of different types; renaming properties on a custom WinForms control that a PropertyMap still references; assuming WPF property casing/names on a WinForms control; .NET version changes removing or renaming a control property.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

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• ' '.' ' is a property without a getter and is not a valid…
• ' '.' ' is a property without a getter and is not a valid…
• ' '.' ' is a property without a getter and is not a valid…
• ' ' ContentType is not valid.

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/3f1c837fddd95978. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/WindowsFormsIntegration/System/Windows/Integration/PropertyMap.cs:140

        /// <param name="propertyName">A string containing the name of the host control property to translate.</param>
        /// <param name="translator">A PropertyTranslator delegate which will be called when the specificied property changes.</param>
        public void Add(String propertyName, PropertyTranslator translator)
        {
            if (Contains(propertyName))
            {
                throw new InvalidOperationException(string.Format(CultureInfo.CurrentCulture, SR.WFI_PropertyMappingExists, propertyName));
            }
            this[propertyName] = translator;
        }

        private void ThrowIfPropertyDoesntExistOnSource(string propertyName)
        {
            if (SourceObject != null)
            {
                if (GetProperty(propertyName) == null)
                {
                    // Property 'Foreground' doesn't exist on type 'Window'
                    throw new ArgumentException(string.Format(CultureInfo.CurrentCulture, SR.WFI_PropertyDoesntExist, propertyName, SourceObject.GetType().FullName));
                }
            }
        }

        /// <summary>
        ///     Runs the PropertyTranslator for the given property, based on the 
        ///     SourceObject's current value.
        /// </summary>
        /// <param name="propertyName"></param>
        public void Apply(string propertyName)
        {
            if (Contains(propertyName))
            {
                ThrowIfPropertyDoesntExistOnSource(propertyName);
                PropertyInfo property = GetProperty(propertyName);
                if (property != null)
                {
                    RunTranslator(this[propertyName], SourceObject, propertyName, property.GetValue(SourceObject, null));

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