DynamicNodeProviderBase + Pagination - asp.net-mvc

Question

I have ASP.NET MVC Project and I have some module. Some modules have pagination. For test and understand MvcSiteMapProvider I working with one module Forum and created ForumDynamicNodeProvider class
public class ForumDynamicNodeProvider : DynamicNodeProviderBase
{
private readonly IForumsService _forumsService;
public ForumDynamicNodeProvider(IForumsService forumsService)
{
this._forumsService = forumsService;
}
public override IEnumerable<DynamicNode> GetDynamicNodeCollection(ISiteMapNode node)
{
string rootTitle = ManagerLocalization.Get("Forums", "FORUMS");
var nodes = new List<DynamicNode>
{
new DynamicNode
{
Title = rootTitle,
Controller = "Forums",
Action = "Index",
Key = "forum_home"
}
};
var forums = this._forumsService.GetForums<ForumNode>().ToList();
var topics = this._forumsService.GetTopics<TopicNode>().ToList();
foreach (var forum in forums)
{
var parentForum = this.GetParentForum(forums, forum);
string parentKey = parentForum?.Id.ToString() ?? "home";
var forumRouteValue = new Dictionary<string, object> { { "forumName", forum.NameTranslit } };
nodes.Add(new DynamicNode
{
Key = $"forum_{forum.Id}",
ParentKey = $"forum_{parentKey}",
Title = forum.Name,
Controller = "Forums",
Action = "ShowForum",
RouteValues = forumRouteValue
});
}
foreach (var topic in topics)
{
var forum = forums.FirstOrDefault(item => item.Id == topic.ForumId);
var forumRouteValue = new Dictionary<string, object> { { "forum", forum.NameTranslit }, { "topicName", topic.TitleTranslite }, {"page", 0 } };
nodes.Add(new DynamicNode
{
Key = $"topic_{topic.Id}",
ParentKey = $"forum_{topic.ForumId}",
Title = topic.Title,
Controller = "Forums",
Action = "ShowTopic",
RouteValues = forumRouteValue
});
}
return nodes;
}
private ForumNode GetParentForum(List<ForumNode> forums, ForumNode forum)
{
if (forum.ForumId > 0)
{
return forums.FirstOrDefault(item => item.Id == forum.ForumId);
}
return null;
}
}
But I can't found a good decision for pagination. For easy I can use page prefix for key and make duplicate DynamicNode. But it's bad idea, because when I have example 1000 topics and each topic have 20 page I must create 20000 DynamicNode. Maybe have other decision?

Answer 1

For ambient context (such as page number) you can use PreservedRouteParameters to force a match on any value for the specified keys. These keys match either route values or query string parameters from the request (route values take precedence if they are the same).
foreach (var forum in forums)
{
var parentForum = this.GetParentForum(forums, forum);
string parentKey = parentForum?.Id.ToString() ?? "home";
var forumRouteValue = new Dictionary<string, object> { { "forumName", forum.NameTranslit } };
// Always match the "page" route value regardless of its value
var forumPreservedRouteParameters = new List<string>() { "page" };
nodes.Add(new DynamicNode
{
Key = $"forum_{forum.Id}",
ParentKey = $"forum_{parentKey}",
Title = forum.Name,
Controller = "Forums",
Action = "ShowForum",
RouteValues = forumRouteValue,
PreservedRouteParameters = forumPreservedRouteParameters
});
}
NOTE: When you use PreservedRouteParameters, they are included in the generated URL from the current request if provided and not included in the URL if not provided in the request. Therefore, if you have more than one page number in the same ancestry you need to have a separate route key name for each one or the current page number will be passed to the ancestor nodes from the current request.