dotnet/wpf · error · ArgumentNullException

stylusPointPropertyInfo

Error message

stylusPointPropertyInfo

What it means

The internal static StylusPointPropertyInfo.AreCompatible method throws ArgumentNullException (with the legacy string literal 'stylusPointPropertyInfo') when either of the two info arguments is null. Both arguments are required to compare property compatibility.

Solutions

  1. Ensure both StylusPointPropertyInfo instances are created before calling comparison code
  2. Filter nulls out of property info collections before compat checks
  3. Wrap the call and supply default property info (StylusPointPropertyInfoDefaults) for missing entries

Example fix

// before
bool ok = StylusPointPropertyInfo.AreCompatible(info1, info2); // info2 may be null
// after
bool ok = info1 != null && info2 != null && StylusPointPropertyInfo.AreCompatible(info1, info2);
Defensive patterns

Strategy: type-guard

Validate before calling

if (info1 == null || info2 == null) return false; // or substitute defaults

Type guard

static bool IsNonNull(StylusPointPropertyInfo i) => i != null;

Try / catch

try { bool ok = StylusPointPropertyInfo.AreCompatible(a, b); }
catch (ArgumentNullException) { /* handle missing property info */ }

Prevention

When it happens

Trigger: Invoking AreCompatible internally (e.g. from StylusPointDescription comparison paths) with a null first or second StylusPointPropertyInfo.

Common situations: Custom stylus property tables containing null entries; code that builds property info arrays lazily and passes uninitialized slots into description-compat checks.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/448f831160c83294. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationCore/System/Windows/Input/Stylus/Common/StylusPointPropertyInfo.cs:111

            internal set { _resolution = value; }
        }

        /// <summary>
        /// Unit
        /// </summary>
        public StylusPointPropertyUnit Unit
        {
            get { return _unit; }
        }

        /// <summary>
        /// Internal helper method for comparing compat for two StylusPointPropertyInfos
        /// </summary>
        internal static bool AreCompatible(StylusPointPropertyInfo stylusPointPropertyInfo1, StylusPointPropertyInfo stylusPointPropertyInfo2)
        {
            if (stylusPointPropertyInfo1 == null || stylusPointPropertyInfo2 == null)
            {
                throw new ArgumentNullException("stylusPointPropertyInfo");
            }

            Debug.Assert((  stylusPointPropertyInfo1.Id != StylusPointPropertyIds.X &&
                            stylusPointPropertyInfo1.Id != StylusPointPropertyIds.Y &&
                            stylusPointPropertyInfo2.Id != StylusPointPropertyIds.X &&
                            stylusPointPropertyInfo2.Id != StylusPointPropertyIds.Y),
                            "Why are you checking X, Y for compatibility?  They're always compatible");
            //
            // we only take ID and IsButton into account, we don't take metrics into account
            //
            return (stylusPointPropertyInfo1.Id == stylusPointPropertyInfo2.Id &&
                    stylusPointPropertyInfo1.IsButton == stylusPointPropertyInfo2.IsButton);
        }
    }
}

View on GitHub (pinned to 81131a70a4)