PrismLibrary/Prism · error · ArgumentNullException

uri

Error message

uri

What it means

UriParsingHelper.Parse throws ArgumentNullException with parameter name 'uri' when passed a null string. Note the docs say null-or-empty, but the code only checks null; an empty string is passed to new Uri and would fail later.

Solutions

1. Ensure a non-null uri string is passed
2. Check the value before navigating: if (uri is not null) navigationService.NavigateAsync(uri)
3. Fix the binding/data source that produced null

Example fix

// before
await _navigationService.NavigateAsync(_nextUri); // _nextUri null
// after
if (_nextUri is not null)
    await _navigationService.NavigateAsync(_nextUri);

if (string.IsNullOrWhiteSpace(uri))
    throw new ArgumentException("uri must be a non-empty string", nameof(uri));
await navigationService.NavigateAsync(uri);

bool isNavigableUri(string uri) => !string.IsNullOrEmpty(uri);

try { await navigationService.NavigateAsync(uri); }
catch (ArgumentNullException ex) when (ex.ParamName == "uri") { /* fallback navigation */ }

When it happens

Trigger: Calling UriParsingHelper.Parse(null), typically via NavigationService navigation APIs given a null URI, or CommandParameter-bound URIs that never received a value.

Common situations: XAML bindings to a navigation command whose Uri property was never set; view-model navigation calls with null segment strings after failed configuration.

Related errors

• source
• configureSegment
• Cannot process an absolute Navigation Uri when navigating…
• regionNavigationContentLoader
• navigationCallback

AI-assisted analysis of PrismLibrary/Prism@358118cd64 (2026-09-15). Data as JSON: /api/errors/3d491d48398f7449. Report an issue: GitHub.

Appendix: source

Thrown at src/Prism.Core/Common/UriParsingHelper.cs:161

        /// <param name="uri">The URI.</param>
        public static INavigationParameters ParseQuery(Uri uri)
        {
            var query = GetQuery(uri);

            return new NavigationParameters(query);
        }

        /// <summary>
        /// Parses a uri string to a properly initialized Uri for Prism
        /// </summary>
        /// <param name="uri">A uri string.</param>
        /// <returns>A <see cref="Uri"/>.</returns>
        /// <exception cref="ArgumentNullException">Throws an <see cref="ArgumentNullException"/> when the string is null or empty.</exception>
        public static Uri Parse(string uri)
        {
            if (uri == null)
            {
                throw new ArgumentNullException(nameof(uri));
            }

            return uri.StartsWith("/", StringComparison.Ordinal)
                ? new Uri("http://localhost" + uri, UriKind.Absolute)
                : new Uri(uri, UriKind.RelativeOrAbsolute);
        }

        /// <summary>
        /// This will provide the existing <see cref="Uri"/> if it is already Absolute, otherwise
        /// it will build a new Absolute <see cref="Uri"/>.
        /// </summary>
        /// <param name="uri">The source <see cref="Uri"/>.</param>
        /// <returns>An Absolute <see cref="Uri"/>.</returns>
        public static Uri EnsureAbsolute(Uri uri)
        {
            if (uri.IsAbsoluteUri)
            {
                return uri;

View on GitHub (pinned to 358118cd64)