PrismLibrary/Prism · error · ArgumentNullException

ArgumentNullException(nameof(target))

Error message

ArgumentNullException(nameof(target))

What it means

The same RequestNavigate(string target, callback) overload validates target immediately after validating navigation; passing a null target string throws ArgumentNullException(nameof(target)). Prism parses the string into a Uri (RelativeOrAbsolute) right after the check.

Solutions

1. Validate the target string before calling (string.IsNullOrEmpty) and fall back to a default view.
2. Fix the source producing the null name (binding, config, navigation parameter).
3. Use nameof(SomeView) or constants for view names instead of dynamic strings.

Example fix

// before
var target = navParams["destination"] as string;
region.RequestNavigate(target, r => {}); // target may be null
// after
var target = navParams["destination"] as string ?? "Home";
region.RequestNavigate(target, r => {});

if (string.IsNullOrEmpty(target))
    target = "Home"; // default view

try { region.RequestNavigate(target, r => {}); }
catch (ArgumentNullException ex) { logger.LogWarning(ex, "Null navigation target"); }

When it happens

Trigger: Calling RequestNavigate(navigation, null, callback) — commonly when the target view name is built dynamically (from a binding, config value, or method result) and evaluates to null.

Common situations: Navigation target taken from a bound property, query-string value, or settings key that is unset; string interpolation that produced null via ToString of null object in older code paths.

Related errors

• ArgumentNullException(nameof(navigation))
• ArgumentNullException for 'regionName'
• ArgumentNullException for 'regionTarget'
• ArgumentNullException for 'target'
• ArgumentNullException for 'view'

AI-assisted analysis of PrismLibrary/Prism@358118cd64 (2026-09-15). Data as JSON: /api/errors/62ca363c6ac4ef38. Report an issue: GitHub.

Appendix: source

Thrown at src/Prism.Core/Navigation/Regions/NavigationAsyncExtensions.cs:46

        /// <param name="target">The navigation target</param>
        public static void RequestNavigate(this INavigateAsync navigation, string target)
        {
            RequestNavigate(navigation, target, nr => { });
        }

        /// <summary>
        /// Initiates navigation to the target specified by the <paramref name="target"/>.
        /// </summary>
        /// <param name="navigation">The navigation object.</param>
        /// <param name="target">The navigation target</param>
        /// <param name="navigationCallback">The callback executed when the navigation request is completed.</param>
        public static void RequestNavigate(this INavigateAsync navigation, string target, Action<NavigationResult> navigationCallback)
        {
            if (navigation == null)
                throw new ArgumentNullException(nameof(navigation));

            if (target == null)
                throw new ArgumentNullException(nameof(target));

            var targetUri = new Uri(target, UriKind.RelativeOrAbsolute);

            navigation.RequestNavigate(targetUri, navigationCallback);
        }

        /// <summary>
        /// Initiates navigation to the target specified by the <see cref="Uri"/>.
        /// </summary>
        /// <param name="navigation">The navigation object.</param>
        /// <param name="target">The navigation target</param>
        public static void RequestNavigate(this INavigateAsync navigation, Uri target)
        {
            if (navigation == null)
                throw new ArgumentNullException(nameof(navigation));

            navigation.RequestNavigate(target, nr => { });
        }

View on GitHub (pinned to 358118cd64)