dotnet/wpf · error · ArgumentException

SR.AbsoluteUriOnly

Error message

SR.AbsoluteUriOnly

What it means

WebBrowser.Navigate(Uri) requires an absolute URI. When the source Uri's IsAbsoluteUri is false, the method throws ArgumentException because a relative URI cannot be resolved to an externally visible navigation target without a base. This is an eager argument-validation failure inside DoNavigate, reached via Navigate.

Solutions

  1. Ensure the Uri is absolute: new Uri("https://example.com/page.html") or new Uri(str, UriKind.Absolute).
  2. Resolve relative URIs against a base before navigating: new Uri(baseUri, relativeUri).
  3. Use the Navigate(string) overload with a fully qualified URL string.
  4. Validate Uri.IsAbsoluteUri before calling Navigate and surface a friendly message.

Example fix

// before
browser.Navigate(new Uri("example.com/page"));
// after
browser.Navigate(new Uri("https://example.com/page", UriKind.Absolute));
Defensive patterns

Strategy: validation

Validate before calling

public static void NavigateSafe(this WebBrowser wb, Uri uri)
{
    if (uri == null) throw new ArgumentNullException(nameof(uri));
    if (!uri.IsAbsoluteUri)
        throw new ArgumentException("URI must be absolute", nameof(uri));
    wb.Navigate(uri);
}

Type guard

static bool IsNavigable(Uri u) => u != null && u.IsAbsoluteUri;

Try / catch

try { browser.Navigate(uri); } catch (ArgumentException ex) when (ex.ParamName == "source") { Log.Error($"Navigation aborted: '{uri}' is not an absolute URI."); }

Prevention

When it happens

Trigger: Calling webBrowser.Navigate(new Uri("page.html")) or Navigate(someRelativeUri); passing a Uri built from a string without a scheme; navigating with a Uri created via new Uri(relativeString, UriKind.Relative).

Common situations: Hard-coding paths like 'www.example.com' (missing scheme), reading URLs from config without scheme, constructing URIs by string concatenation that drop the 'http://' prefix.

Understand the failure class

Background: "Invalid URL" errors: why new URL(), URI.parse, and reqwest::Url reject your string — missing scheme, whitespace, and bad path format — this error's family across 39 libraries.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/21ce3e468af1aa20. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Controls/WebBrowser.cs:870

            // TFS  - Launching a navigation from the Navigating event handler causes reentrancy.
            // For more info, see WebBrowser.LastNavigation. Here we generate a new navigation identifier which
            // is used to detect reentrant calls during handling of the Navigating event.
            LastNavigation = Guid.NewGuid();

            // When source set to null or navigating to stream/string, we navigate to "about:blank" internally.
            if (source == null)
            {
                NavigatingToAboutBlank = true;
                source = new Uri(AboutBlankUriString);
            }
            else
            {
                CleanInternalState();
            }

            if (!source.IsAbsoluteUri)
            {
                throw new ArgumentException(SR.AbsoluteUriOnly, nameof(source));
            }

            // Resolve Pack://siteoforigin.
            if (PackUriHelper.IsPackUri(source))
            {
                source = BaseUriHelper.ConvertPackUriToAbsoluteExternallyVisibleUri(source);
            }

            // figure out why BrowserNavConstants.NewWindowsManaged does not work.
            object flags = (object)null; // UnsafeNativeMethods.BrowserNavConstants.NewWindowsManaged;

            // Fix for inability to navigate to a URI containing invalid UTF-8 sequences
            // BindUriHelper.UriToString does use Uri.GetComponents with the UriFormat.SafeUnescaped flag passed in,
            // causing invalid UTF-8 sequences to get dropped, resulting in a strictly speaking valid URI but for
            // some websites this causes breakage. Therefore we allow ignoring this treatment by means of string-
            // based overloads for the public Navigate methods, creating a Uri internally and using AbsoluteUri
            // to get back the URI string to feed in to the WebOC in its original form. WinForms has a similar
            // set of overloads to enable this scenario.

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