gistfile1.txt

public string GetProductCategory()
{
    var category = GetFirstCategory(CurrentDocument);
    
    if (category != null)
    {
        var qsvalue = category.CategoryID;

        return "?subject=" + qsvalue;
    }
    else
    {
        return String.Empty;
    }
}

public SettingsProvider.BaseInfo GetFirstCategory(TreeNode tn)
{
    if (tn.Categories != null)
    {
        if (tn.Categories.Count > 0)
        {
            return (CategoryInfo)tn.Categories.FirstItem;
        }
        else
        {
            return null;
        }
        
    }
    else if (!tn.Parent.IsRoot())
    {
        return GetFirstCategory(tn.Parent);
    }
    else
    {
        return null;
    }
}