So i'm trying to build a User multi-select in order to get the participants to a project. This is my code:

  <form asp-page-handler="ProjectModalPartial">
                @*numele metodei*@
                <input name="IsValid" type="hidden" value="@ViewData.ModelState.IsValid.ToString()" />
                <div >
                    <label asp-for="ProjectsModel.ProjectName">Title</label>
                    <input asp-for="ProjectsModel.ProjectName"  placeholder="MyProject1" />
                    <span asp-validation-for="ProjectsModel.ProjectName" ></span>
                </div>
                <br />
                <div >
                    <label asp-for="ProjectsModel.ProjectDescription">Description</label>
                    <textarea asp-for="ProjectsModel.ProjectDescription"  rows="3" placeholder="This is my first project"></textarea>
                    <span asp-validation-for="ProjectsModel.ProjectDescription" ></span>
                </div>
                <br />

                <div >

                    <label asp-for="ProjectsModel.MultiValues">Project participants</label>
                    <select multiple="multiple"  id="listbox1" asp-for="ProjectsModel.MultiValues" asp-items="@Model.Items" style="width: 470px;">
                     
                    </select>
                    <span asp-validation-for="ProjectsModel.MultiValues" ></span>

                </div>
            </form>

The page:

 public ApplicationDbContext _context;

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

    public List<Project> ProjectList { get; private set; } = new List<Project>();
    [BindProperty]
    public ProjectsModel ProjectsModel { get; set; }
    public List<User> UserList { get; private set; } = new List<User>();

    public IEnumerable<SelectListItem> Items { get; set; }
    = new List<SelectListItem>();
    public void OnGet()
    {

        ProjectList =  _context.Projects.ToList();
        Items = (from usr in this._context.Users
                 select new SelectListItem
                 {
                     Text = usr.Email.ToString(),
                     Value = usr.Id.ToString()
                 }).ToList();


    }

    public IActionResult OnPostProjectModalPartial()
    {
        Items = (from usr in this._context.Users
                 select new SelectListItem
                 {
                     Text = usr.Email.ToString(),
                     Value = usr.Id.ToString()
                 }).ToList();

        if (ModelState.IsValid)
        {
            var project = new Project
            {
                ProjectName = ProjectsModel.ProjectName,
                ProjectDescription = ProjectsModel.ProjectDescription,
                Created = DateTime.Now,
                Active = true,
                ProjectCreatorId = User.FindFirst(ClaimTypes.NameIdentifier).Value

            };
            _context.Projects.Add(project);
            _context.SaveChanges();
            foreach (var person in Items)
            {
                _context.ProjectParticipants.Add(new ProjectParticipant
                {
                    ProjectId = project.Id,
                    UserId = person.Value
                });


            }
            _context.SaveChanges();
        }
        return Page();
    }

And the model:

   public class ProjectsModel
{
    public int Id { get; set; }
    [Required]
    public string ProjectName { get; set; }
    [Required]
    public string ProjectDescription { get; set; }
    public DateTime Created { get; set; }
    public bool Active { get; set; }

    public string ProjectCreatorId { get; set; }

    [Required(ErrorMessage = "You must select atleast one participant")]
    public List<User> ProjectParticipants { get; set; }

    public IEnumerable<string> MultiValues { get; set; }


}

However, when i put a breakpoint inside the foreachloop of OnPostProjectModalPartial i can see the list is populated with all the users but none of them is selected. What am i doing wrong? Do i need some jquery script to make this work?

CodePudding user response：

You need indicate the property of your model associated to the selected option:

<select multiple="multiple" 
    
   id="listbox1" 
   asp-for="UserId" // <-- This property
   asp-items="@Model.Items" 
   style="width: 470px;">

And add UserId property to your class:

public int UserId { get; set; }

Then, in the post, your model UserId has the selected user id and you can do a query to get all info that you need about that user.

NOTE: In your current OnPostProjectModalPartial, you are making a query in your database but without any kind of selection info getted from the post.

CodePudding user response：

If you want some of the list of users selected you need to change your code, this piece of code in the page part

ORIGINAL

foreach (var person in Items)
{
    _context.ProjectParticipants.Add(new ProjectParticipant
    {
         ProjectId = project.Id,
         UserId = person.Value
     });
} //ORIGINAL

Into this: Filtering only the Model.Iems selected

foreach (var person in model.Items.Where(item=> item.Selected))
{
    _context.ProjectParticipants.Add(new ProjectParticipant
    {
         ProjectId = project.Id,
         UserId = person.Value
     });
}

Also you did'nt need to go get the list again from database, you got it in the model