I would prefer a solution where it is not as specific to a single culture.
Like CultureInfo.CurrentUICulture.TextInfo.IsRightToLeft

this.Body.Attributes.Add will replace the attribute, we need to get its current value, append the class and then .Add the attribute again.

Thank you for the feedback. 👍

You're right – we can update the code as below to ensure that the class attribute is not overwritten and rtl is only added if it's not already included:

if (CultureInfo.CurrentUICulture.TextInfo.IsRightToLeft)
{
    string existingClass = this.Body.Attributes["class"];

    if (string.IsNullOrEmpty(existingClass))
    {
        this.Body.Attributes.Add("class", "rtl ");
    }
    else if (!existingClass.Contains("rtl"))
    {
        this.Body.Attributes["class"] = existingClass + " rtl ";
    }
}

Please let me know if you prefer a utility method for class handling to keep it cleaner.

If you agree with this change, I can update the PR accordingly.

When the page hits a 404 error, the system's default culture falls back to en-US.
The solution I found was to check for "fa-IR" and explicitly set the Persian culture like this:

if (this.PortalSettings.CultureCode == "fa-IR")
{
    var newCulture = Services.Localization.Persian.PersianController.GetPersianCultureInfo();
    System.Threading.Thread.CurrentThread.CurrentUICulture = newCulture;
}

Do you have a better approach to ensure the correct culture is set for 404 pages?

I think (but have not tried it) this line of the web.config defines the fallback language for when DNN can't know the language (which may be the case for 404 pages).

<globalization culture="en-US" uiCulture="en" requestEncoding="UTF-8" responseEncoding="UTF-8" fileEncoding="UTF-8" />

If that is not the case then I guess we would need to figure out for the 404 page. If we know the portal info in that context we could use the portal primary language (which could be a different PR maybe.

Your first change looks good to me if you can adjust the PR, I am fine with the described changes there.

Alright, I will create a new PR for the rtl class