How would I have two model classes in one view?

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The problem I am running into is using two model classes in one view. I have tried using a class called AllModels as a view model but I get this exception:

InvalidOperationException: The model item passed into the ViewDataDictionary is of type 'System.Collections.Generic.List`1[Project2.Models.Entities.ProjectRole]', but this ViewDataDictionary instance requires a model item of type 'System.Collections.Generic.IEnumerable`1[Project2.Models.Entities.AllModels]'.

I have looked at many different resources but cannot seem to figure it out for my code. At this point, I am not sure what I am missing or what I am doing wrong. Any help/advice is much appreciated! Thanks.

What I have tried:

Model Classes

public class Person
    {
        public int Id { get; set; }

        [Required]
        [MaxLength(30)]
        public string FirstName { get; set; }

        [Required]
        [MaxLength(30)]
        public string MiddleName { get; set; }

        [Required]
        [MaxLength(30)]
        public string LastName { get; set; }

        [Required]
        public string Email { get; set; }

        public ICollection<ProjectRole> ProjectRoles { get; set; }
    }

public class Project
    {
        public int Id { get; set; }

        [Required]
        [MaxLength(30)]
        public string Name { get; set; }

        [Required]
        public DateTime StartDate { get; set; }

        [Required]
        public DateTime DueDate { get; set; }

        public ICollection<ProjectRole> ProjectRoles { get; set; }
    }

public class ProjectRole
    {
        public int Id { get; set; }

        [Required]
        public double HourlyRate { get; set; }

        [ForeignKey("Person")]
        public int PersonId { get; set; }

        [ForeignKey("Project")]
        public int ProjectId { get; set; }

        [ForeignKey("AppRole")]
        public int RoleId { get; set; }

    }

Controller Code

[Authorize(Roles = "Member")]
    public class ProjectRolesController : Controller
    {
        private readonly ApplicationDbContext _context;

        public ProjectRolesController(ApplicationDbContext context)
        {
            _context = context;
        }

        private void PopulateLookups(ProjectRole projectRole)
        {
            var projects = _context.Projects.OrderBy(p => p.Name).ToList();
            ViewBag.ProjectId = projects.Select(p => new SelectListItem
            {
                Value = p.Id.ToString(),
                Text = p.Name,
                Selected = p.Id == projectRole.ProjectId
            });
            var people =
                _context.People.OrderBy(p => p.LastName).ThenBy(p => p.FirstName).ToList();
            ViewBag.PersonId = people.Select(p => new SelectListItem
            {
                Value = p.Id.ToString(),
                Text = $"{p.LastName}, {p.FirstName} {p.MiddleName}",
                Selected = p.Id == projectRole.PersonId,
            });
        }

        public async Task<IActionResult> Index()
        {
            
            return View(await _context.ProjectRoles.ToListAsync());
        }
        //...rest of the code below
    }

And my View code

@model IEnumerable< Project2.Models.Entities.AllModels>



@{
    ViewData["Title"] = "Index";
}

<div class="text-center">
    <a href="/"><button>Home</button></a> |
    <a href="../People"><button>Manage People</button></a> |
    <a href="../People/Report"><button>View People Report</button></a> |
    <a href="../Projects"><button>Manage Projects</button></a> |
    <a href="../Projects/Report"><button>View Project Report</button></a> |
    <a href="../ProjectRoles"><button>Manage Project Role</button></a>
</div>

<p>
    <a asp-action="Create">Create New</a>
</p>
<table class="table">
    <thead>
        <tr>
            <th>
                Person Name
            </th>
            <th>
                Project Name
            </th>
            <th>
                @Html.DisplayNameFor(model => model.ProjectRole.HourlyRate)
            </th>
            <th>
                @Html.DisplayNameFor(model => model.ProjectRole.RoleId)
            </th>
            <th></th>
        </tr>
    </thead>
    <tbody>
        @foreach (var item in Model)
        {
            <tr>
                <td>
                    @Html.DisplayFor(modelItem => item.Person.FirstName + " " + item.Person.LastName)
                </td>
                <td>
                    @Html.DisplayFor(modelItem => item.Project.Id)
                </td>
                <td>
                    @Html.DisplayFor(modelItem => item.ProjectRole.HourlyRate)
                </td>
                <td>
                    @Html.DisplayFor(modelItem => item.ProjectRole.RoleId)
                </td>
                <td>
                    <a asp-action="Edit" asp-route-id="@item.ProjectRole.Id">Edit</a> |
                    <a asp-action="Details" asp-route-id="@item.ProjectRole.Id">Details</a> |
                    <a asp-action="Delete" asp-route-id="@item.ProjectRole.Id">Delete</a>
                </td>
            </tr>
        }
    </tbody>
</table>

Posted 3-Nov-21 9:10am

mrnewguy2020

Updated 4-Nov-21 10:25am

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Comments

[no name] 4-Nov-21 1:36am

If you had an "AllModels" class, why didn't you show it? The error says it "doesn't exist", and all the evidence (or lack thereof) confirms that.

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#realJSOP · Answer 1 · 2021-11-04T10:25:00

You could create an object that can have objects added to it. Given the following:

C#

public class Model1
{
    public Model1(){ }
}
public class Model2
{
    public Model2(){ }
}
public class Model3
{
    public Model3(){ }
}

public class ModelBag
{
    public List<object> Models { get; set; }
    public ModelBag ()
    {
        this.Models = new List<object>();
    }

    public void Add(object obj)
    {
        if (obj != null) this.Models.Add(obj);
    }

    public T Get<T>()
    {
        var found = this.Models.OfType<T>().Select(x=>x);
        return (found.Count()>0) ? found.First() : default(T);
    }
}

You can do this:

C#

// create the model bag
ModelBag bag = new ModelBag();

// add a couple of models
bag.Add(new Model1());
bag.Add(new Model2());

// retrieve the desired models
Model1 bagModel1 = bag.Get<Model1>(); // this will return the Model1 iobject
Model3 bagModel3 = bag.Get<Model3>(); // this will return a null value

In the usage example above, you add model1 and model2 to the bag, and attempt to retrieve either one will result in a non-null reference. Because we didn't add a Model3 object to the bag, trying to retrieve it will result in a null reference.

I leave it as an exercise for the programmer to make the ModelBag suit his needs (allow/disallow duplicates of a given object type.

EDIT ==================================

I wrote an article with a more complete code sample.

Multiple Models In a MVC View[^]