When on a search results page and use the language switcher, the search results are lost.

The language switcher does not include the query parameters needed for search in the URL.

Using the in page options in the search results widget to filter for results in a different language doesn’t cause the page itself to switch to the other language, just the search results.

For example selecting "Show results in Spanish", the results are in Spanish, but the rest of the page is not.

The .NET Core Renderer doesn't have language selector widget out of the box. It needs to be implemented as per below sample:

https://github.com/Sitefinity/sitefinity-aspnetcore-mvc-samples/tree/master/src/language-selector

This is expected behavior.

Use the below workaround.

In Program.cs:

1. Add IHttpContextAccessor service:

builder.Services.AddHttpContextAccessor();

In LanguageSelectorModel.cs:

1. Add a variable:

private readonly IHttpContextAccessor _httpContextAccessor;

2. Assign the variable in the constructor:

public LanguageSelectorModel(IHttpContextAccessor httpContextAccessor, IRequestContext requestContext, IRestClient restClient)
{
_httpContextAccessor = httpContextAccessor;
this.requestContext = requestContext;
this.restClient = restClient;
}

3. Add the below code in GetViewModel:

3.1.

var request = _httpContextAccessor.HttpContext.Request;

3.2. in the foreach iterating the available languages:

if (request.QueryString.HasValue)
{
	var query = request.Query;

	if (query.Keys.Contains("indexCatalogue"))
	{
		string resolvedQueryParams = this.ResolveQueryParams(request.QueryString.Value, language);

		var entry = new LanguageEntry()
		{
			Name = ci.EnglishName,
			Value = ci.Name,
			Selected = ci.Name == this.requestContext.Culture.Name,
			PageUrl = pageNode.ViewUrl + resolvedQueryParams
		};


	viewModel.Languages.Add(entry);
	
	}
}
else
{
  // the default behavior
}

3.3. Add ResolveQueryParams method:

private string ResolveQueryParams(string queryString, string language)
{
    string[] queryParams = queryString.Split('&');

    string resolvedQueryParams = "";

    for (int i = 0; i < queryParams.Length; i++)
    {
        if (queryParams[i].Length >= 11 && queryParams[i].Substring(0, 11) == "sf_culture=")
        {
            queryParams[i] = "sf_culture=" + language;

            if (i == queryParams.Length - 1)
            {
                resolvedQueryParams += queryParams[i];
                continue;
            }
            else
            {
                resolvedQueryParams += queryParams[i] + "&";
                continue;
            }
        }

        if (i == queryParams.Length - 1)
        {
            resolvedQueryParams += queryParams[i];
        }
        else
        {
            resolvedQueryParams += queryParams[i] + "&";
        }

    }

    return resolvedQueryParams;

}