dotnet/wpf · error · ArgumentNullException

Argument 'propertyName' cannot be null or empty.

Error message

Argument 'propertyName' cannot be null or empty.

What it means

Besides the exception, PropertyMappingExceptionEventArgs requires the name of the property whose mapping failed. An empty or null propertyName cannot identify the failing mapping, so the constructor throws ArgumentNullException naming 'propertyName'.

Solutions

1. Pass the actual non-empty property name from the translation context.
2. Guard: if (!string.IsNullOrEmpty(propName)) new PropertyMappingExceptionEventArgs(ex, propName, value);
3. Ensure the loop/handler carries the property name through to the event-args construction.

Example fix

// before
new PropertyMappingExceptionEventArgs(ex, currentProperty, value); // currentProperty may be ""
// after
if (!string.IsNullOrEmpty(currentProperty))
    new PropertyMappingExceptionEventArgs(ex, currentProperty, value);

if (string.IsNullOrEmpty(propertyName))
    throw new ArgumentException("propertyName required for mapping error args");
var args = new PropertyMappingExceptionEventArgs(ex, propertyName, value);

bool IsValidMappingProp(string prop) => !string.IsNullOrEmpty(prop);

try { var e = new PropertyMappingExceptionEventArgs(ex, prop, value); }
catch (ArgumentNullException) { log.Error($"Missing property name for error on value {value}"); }

When it happens

Trigger: Constructing PropertyMappingExceptionEventArgs(ex, null, value) or (ex, "", value) when the caller lost track of which property was being translated (e.g. in a generic loop over mapped properties).

Common situations: Error-handling glue around PropertyMap where the property name variable is only set inside a try block; forwarding a TranslatorAppliedEventArgs property that was empty.

Understand the failure class

Background: "must not be empty", "cannot be empty" — required-field validation errors across open-source libraries — this error's family across 41 libraries.

Related errors

• The exception argument cannot be null.
• ArgumentNullException(nameof(assemblyNames))
• nameof(name)
• SR.EventArgIsNull
• anchorLocator.Parts

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/735fe7c52c6ae3e7. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/WindowsFormsIntegration/System/Windows/Integration/PropertyMappingExceptionEventArgs.cs:28

    /// </summary>
    public class PropertyMappingExceptionEventArgs : IntegrationExceptionEventArgs 
    {
        private string _propertyName;
        private object _propertyValue;

        /// <summary>
        /// Initializes a new instance of the PropertyMappingExceptionEventArgs class.
        /// </summary>
        public PropertyMappingExceptionEventArgs(Exception exception, string propertyName, object propertyValue) 
            : base(false, exception)
        {
            if (exception == null)
            {
                throw new ArgumentNullException(string.Format(CultureInfo.CurrentCulture, SR.WFI_NullArgument, "exception"));
            }
            if (string.IsNullOrEmpty(propertyName))
            {
                throw new ArgumentNullException(string.Format(CultureInfo.CurrentCulture, SR.WFI_ArgumentNullOrEmpty, "propertyName"));
            }
            _propertyName = propertyName;
            _propertyValue = propertyValue;
        }

        /// <summary>
        /// Identifies the property that was being mapped when the exception occurred.
        /// </summary>
        public string PropertyName
        {
            get
            {
                return _propertyName;
            }
        }

        /// <summary>
        /// Specifies the value of the property that was being mapped when the exception occurred.

View on GitHub (pinned to 81131a70a4)