dotnet/wpf · error · ArgumentException

SR.UnsupportedProperty

Error message

SR.UnsupportedProperty

What it means

The PropertyCondition constructor validates the given AutomationProperty against Schema.GetPropertyInfo; unknown properties throw ArgumentException(SR.UnsupportedProperty). PropertyCondition can only be built from properties the UI Automation client schema knows about, because it must map to an unmanaged UIA condition.

Solutions

  1. Build conditions only with known identifiers like AutomationElement.NameProperty or pattern identifier properties
  2. Validate the property id against AutomationProperty references in the schema before constructing the condition
  3. For custom provider properties, search client-side by enumerating elements instead of using PropertyCondition

Example fix

// before
var cond = new PropertyCondition(myCustomProperty, "value"); // ArgumentException
// after
var cond = new PropertyCondition(AutomationElement.AutomationIdProperty, "value");
Defensive patterns

Strategy: validation

Validate before calling

var known = new[]{ AutomationElement.NameProperty, AutomationElement.AutomationIdProperty, AutomationElement.ControlTypeProperty };
if (!known.Contains(property)) return null; // don't build the condition

Try / catch

try { var c = new PropertyCondition(p, v); } catch (ArgumentException) { /* fall back to client-side filter */ }

Prevention

When it happens

Trigger: new PropertyCondition(customOrUnknownProperty, value); passing a property identifier obtained from LookupById for an id not in the client schema; passing an AutomationProperty from a different UIA surface.

Common situations: Constructing search conditions dynamically from config where property names don't map to schema properties; using provider-side or custom-registered properties in client-side conditions; typos in property identifier selection.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/7711a9ac3096492d. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/UIAutomation/UIAutomationClient/System/Windows/Automation/PropertyCondition.cs:127

        #endregion Public Properties


        //------------------------------------------------------
        //
        //  Private Methods
        //
        //------------------------------------------------------

        #region Private Methods

        private void Init(AutomationProperty property, object val, PropertyConditionFlags flags )
        {
            ArgumentNullException.ThrowIfNull(property);

            AutomationPropertyInfo info;
            if (!Schema.GetPropertyInfo(property, out info))
            {
                throw new ArgumentException(SR.UnsupportedProperty);
            }

            // Check type is appropriate: NotSupported is allowed against any property,
            // null is allowed for any reference type (ie not for value types), otherwise
            // type must be assignable from expected type.
            Type expectedType = info.Type;
            if (val != AutomationElement.NotSupported &&
                ((val == null && expectedType.IsValueType)
                || (val != null && !expectedType.IsAssignableFrom(val.GetType()))))
            {
                throw new ArgumentException(SR.Format(SR.PropertyConditionIncorrectType, property.ProgrammaticName, expectedType.Name));
            }

            if ((flags & PropertyConditionFlags.IgnoreCase) != 0)
            {
                Misc.ValidateArgument(val is string, nameof(SR.IgnoreCaseRequiresString));
            }

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