partial view returns Value cannot be null

Question

User1051638994 posted

Hello,

I am trying to display a partial view with data from my db using a view model.

Here is my View model

   public class VMTicketReply
    {
        public IEnumerable<Ticket> Tickets { get; set; }

        public IEnumerable<Replies> Replies { get; set; }

        public IEnumerable<User> Users { get; set; }

        public IEnumerable<Accepter> Accepters { get; set; }
    }

My razor view

 @await Html.PartialAsync("_LoginPartial.cshtml", new VMTicketReply())

And my partial view

@model HelpDesk.Models.VMTicketReply

  
@foreach (var item in Model.Tickets.Where(t=>t.TicketIsSeen = false))
                    {
                        <a asp-action="Details" asp-route-id="@item.TicketID">@item.TicketContent></a>

                    }

But always retuns ArgumentNullException: Value cannot be null. Any Idea? Thank you

Answer 1

User475983607 posted

mspace

But always retuns ArgumentNullException: Value cannot be null. Any Idea? Thank you

Because you are specifically passing null/empty IEnumerable properties!

 @await Html.PartialAsync("_LoginPartial.cshtml", new VMTicketReply())

See the C# programming guide to learn C# classes and constructors.

https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/constructors

Answer 2

User1051638994 posted

Thank you for your reply.

If I dont use this

new VMTicketReply()

then I get error to partial view too.

I tried  this

public IEnumerable<Ticket> Tickets { get; set; } = new List<Ticket>();

I dont receive any errors but also the data are not being displayed

Answer 3

User475983607 posted

I dont receive any errors but also the data are not being displayed

Of course there's no data.  You are not populating the model.  

Getting Started Tutorials.

https://docs.microsoft.com/en-us/aspnet/core/tutorials/first-mvc-app/?view=aspnetcore-3.1

https://docs.microsoft.com/en-us/aspnet/core/data/ef-mvc/?view=aspnetcore-3.1

Answer 4

User1312693872 posted

Hi,mspace

But always retuns ArgumentNullException: Value cannot be null. Any Idea? Thank you

I haven't seen any data passing code in your shared code, but you should get the data for the model first, so I made a demo, you can check it:

Model:

    public class VMTicketReply
    {
        public IEnumerable<Ticket> Tickets { get; set; }
    }
    public class Ticket
    {
        public int TicketID { get; set; }
        public string TicketContent { get; set; }
        public bool TicketIsSeen { get; set; }
    }

View:

@model VMTicketReply

@await Html.PartialAsync("_LoginPartial.cshtml", Model.Tickets)

Partial view:

@model IEnumerable<Ticket> 

@foreach (var item in Model)
{
    if (item.TicketIsSeen == false)
    { 
    <a asp-action="Details" asp-route-id="@item.TicketID">@item.TicketContent</a>
    }
}

Controller(if you use a database, then the sql connection sentence should be written in the controller)

public IActionResult Index()
        {
            var data = new VMTicketReply()
            {
                Tickets =new  List<Ticket>()
                {
                    new Ticket{
                    TicketID = 1,
                    TicketContent = "It's a ticket",
                    TicketIsSeen = false
                    },
                    new Ticket{
                    TicketID = 1,
                    TicketContent = "It's a ticket2",
                    TicketIsSeen = true
                    }
                }
            };
            return View(data);
        }

Result:

Best Regards,

Jerry Cai

Answer 5

User1051638994 posted

Thank you for your reply! I understand your logic

but now I get

'IHtmlHelper<dynamic> has no applicable method named but appears to have an extension method by that name. Extension methods cannot be dynamically dispatched. Consider casting the dynamic arguments or calling the extension method without the extension method syntax.

at line 

@await Html.PartialAsync("_LoginPartial.cshtml", Model.Ticket)

Answer 6

User1051638994 posted

Thank you for your help

I used ViewComponents instead of partials and it worked

 

Answer 7

User1312693872 posted

Hi,mspace

I'm glad that you have solved your problem, I suggest you mark the answer which you think is useful, so it will help more people who have the similar problems.

Best Regards,

Jerry Cai