Blazor 8.0 NavigateTo throws an exception

Question

Hello,

I have a language selector that calls the following code and it works like a charm.

On other hand, I want to change the language from within the MainLayout on Initialized event (async) but then the very same code throws an exception of type NavigationException. No further explanation.

var cultureEscaped = languageFromURL == "en" ? "en-US" : "de-DE"; 
_navigationManager.NavigateTo($"Culture/Set?culture={cultureEscaped}&redirectUri=/");

The Culture is Controller and Set is an action.

The idea is to change the language if the language in the URL differs from the CultureInfo language. Maybe I should use another component instead of MainLayout? Please advice.

Thank you!

Answer 1

This is the code that I have at the moment and which throws that exception explained previously.

protected override async Task OnParametersSetAsync()
{

    var languageFromURL = string.Empty;
    var languageFromCulture = CultureInfo.CurrentCulture.TwoLetterISOLanguageName;
    var parts = _navigationManager.ToBaseRelativePath(_navigationManager.Uri.ToString()).Split('/');

    if (parts.Count() > 1)
    {
        languageFromURL = parts[0];

        PageName = parts[1];
    }


    try
    {
        // ensure that language is two letters
        if (languageFromCulture.Length == 2 && languageFromURL.Length == 2)
        {
            if (languageFromURL != languageFromCulture)
            {
                //-- LANGUAGE IN THE URL DIFFERS FROM THE CURRENTLY SELECTED LANGUAGE

                var isPastedRouteFound = false;
                var newLanguage = string.Empty;
                var newRoute = string.Empty;

                using (Microsoft.Data.SqlClient.SqlConnection connection = DatabaseHelpers.NewConnection())
                {
                    connection.Open();
                    using (Microsoft.Data.SqlClient.SqlCommand command = connection.CreateCommand())
                    {
                        command.CommandType = System.Data.CommandType.StoredProcedure;
                        command.CommandText = "blazor_CheckRoute";
                        command.Parameters.AddWithValue("@LanguageFromCulture", languageFromCulture); // language from the culture info
                        command.Parameters.AddWithValue("@LanguageFromURL", languageFromURL); // language from the route/URL
                        command.Parameters.AddWithValue("@PageName", PageName);
                        command.Parameters.Add("@IsRouteFound", System.Data.SqlDbType.Int, 4).Direction = System.Data.ParameterDirection.Output;
                        command.ExecuteNonQuery();
                        if (command.Parameters["@IsRouteFound"].Value != null)
                        {
                            isPastedRouteFound = Convert.ToBoolean(command.Parameters["@IsRouteFound"].Value);
                        }
                    }
                }

                if (isPastedRouteFound == true)
                {
                    var culture = string.Empty;
                    switch (languageFromURL)
                    {
                        case "en":
                            culture = Uri.EscapeDataString("en-US");
                            break;
                        case "de":
                            culture = Uri.EscapeDataString("de-DE");
                            break;
                        case "es":
                            culture = Uri.EscapeDataString("es-ES");
                            break;
                    }


                    _httpContextAccessor.HttpContext.Response.Cookies.Append(
                        CookieRequestCultureProvider.DefaultCookieName,
                        CookieRequestCultureProvider.MakeCookieValue(new RequestCulture(culture, culture)));

                    //-- EXCEPTION IS THROWN WHEN THE LINE BELOW GETS EXECUTED
                    //_navigationManager.NavigateTo(_navigationManager.Uri, true);

                }

            }
        }

    }
    catch (Exception ex)
    {
        Logging.LogError(ex, remark: "");
    }

    await Task.CompletedTask;
}

Database Table (Pages)

Language Route

en contact

de kontakt

es contacto

etc. etc.

Possible scenario: let's say you are currently visiting website.com/es/contacto. Then you paste the following URL to the address bar and hit enter: website.com/en/contact. It redirects you to the new route but the page remains in Spanish. Then if you navigate to another page the language gets changed to EN.

I am certain that I miss something obvious though I am not quite sure what. Thank you!

Answer 2

as you are calling NavigateTo during render it has to throw an error to stop processing (much like aborting a task). don't catch the error, or use OnAfterRender()

also can not update the cookie, as httpcontext is readonly in a blazor app. the request created the signal/r connection and there is no response available. you should handle this logic before the blazor app starts with middleware.