带有Ajax帖子的空模型

Question

I am trying to pass a model to the controller using an ajax post, but every time I do so, the model is null and I lose all the data I am trying to persist.

The ajax call:

$('#next').click(function (e) {
    e.preventDefault();
    var url = '@Url.Action("Manage")'
    var _model = JSON.stringify(@Html.Raw(Json.Encode(Model)));
    var _page = @(Model.pager.CurrentPage + 1);

    $.ajax({
        type: "POST",
        contentType: "application/json; charset=utf-8",
        url: url,
        data: JSON.stringify({ 'model': _model, 'page': _page }),
        success: function(result) {
            console.log(result);
        }
    });
});

When I look at the serialized object, it looks like a correctly formatted JSON object with no errors thrown in the developer console.

The link that is triggering this jQuery call is just a basic action link:

@Html.ActionLink(">", "Manage", "Announcements", null, new { id = "next" })

My model is a little more complicated...

public class ManageViewModel : IEnumerable<EditViewModel>
{
    [Display(Name="Start Date")]
    [DataType(DataType.DateTime)]
    public DateTime? StartDate { get; set; }

    [Display(Name="End Date")]
    [DataType(DataType.DateTime)]
    public DateTime? EndDate { get; set; }

    public string SearchString { get; set; }

    public Pager pager { get; set; }

    public List<EditViewModel> Data { get; set; }
    public List<CategoryViewModel> Categories { get; set; }

    public ManageViewModel()
    {
        Data = new List<EditViewModel>();
        Categories = new List<CategoryViewModel>();
    }

    public IEnumerator<EditViewModel> GetEnumerator()
    {
        return Data.GetEnumerator();
    }

    IEnumerator IEnumerable.GetEnumerator()
    {
        return Data.GetEnumerator();
    }
}

public class Pager
{
    public int TotalItems { get; private set; }
    public int CurrentPage { get; private set; }
    public int PageSize { get; private set; }
    public int TotalPages { get; private set; }
    public int StartPage { get; private set; }
    public int EndPage { get; private set; }

    public Pager(int totalItems, int? page, int pageSize = 10)
    {
        int totalPages = (int)Math.Ceiling((decimal)totalItems / (decimal)pageSize);
        int currentPage = page ?? 1;
        int startPage = currentPage - 5;
        int endPage = currentPage + 4;

        if(startPage <= 0)
        {
            endPage -= (startPage - 1);
            startPage = 1;
        }

        if(endPage > totalPages)
        {
            endPage = totalPages;
            if(endPage > 10)
            {
                startPage = endPage - 9;
            }
        }
        TotalItems = totalItems;
        TotalPages = totalPages;
        CurrentPage = currentPage;
        PageSize = pageSize;
        EndPage = endPage;
        StartPage = startPage;
    }
}

I can't convert the links in to a form because that breaks the pagination. Or maybe I'm just not understanding the full picture here.

Here is the section of the View where the pagination is occurring

if (Model.pager.EndPage > 1)
{
    <div style="color:#337AB7; padding-bottom: 0px;">Page @Model.pager.CurrentPage of @Model.pager.TotalPages</div>
    <ul class="pagination">
        @if (Model.pager.CurrentPage > 1)
        {
            <li>
                @Html.ActionLink("<<", "Manage", new { model = Model, start = Model.StartDate, end = Model.EndDate, query = Model.SearchString }, null)
            </li>
            <li>
                @Html.ActionLink("<", "Manage", new { model = Model, page = Model.pager.CurrentPage - 1, start = Model.StartDate, end = Model.EndDate, query = Model.SearchString }, null)
            </li>
        }
        @for (var _page = Model.pager.StartPage; _page < Model.pager.EndPage + 1; _page++)
        {
            <li class="@(_page == Model.pager.CurrentPage ? "active" : "")">
                @Html.ActionLink(_page.ToString(), "Manage", new { model = Model, page = _page, start = Model.StartDate, end = Model.EndDate, query = Model.SearchString }, null)
            </li>
        }
        @if (Model.pager.CurrentPage < Model.pager.TotalPages)
        {
            <li> 
                @Html.ActionLink(">", "Manage", "Announcements", null, new { id = "next" })
            </li>
            <li>
                @Html.ActionLink(">>", "Manage", new { model = Model, page = Model.pager.TotalPages, start = Model.StartDate, end = Model.EndDate, query = Model.SearchString }, null)
            </li>
        }
    </ul>
}

The action links attempting to pass the model, obviously don't work but I left them because I am focusing on getting one to work, the one listed previously, before getting all the others configured.

I have looked at the following SO posts and have had no luck with them:
Post an MVC model with AJAX?
Model properties null on Ajax post from list box change event
How to send a model in jQuery $.ajax() post request to MVC controller method
Pass Model To Controller using Jquery/Ajax
How to pass model in ajax post request?

Any ideas on how I might be able to do this? I need the model data to persist for searching/filtering which is done through a form. Thank you in advance for taking a look and giving your insights!

Answer 1

You need to include a parameterless constructor for your models. From the screenshot you have sent it seems there isn't a parameterless constructor for public Pager model.