如何实现包含复选框ASP.Net Core MVC的“编辑”操作？

如何解决如何实现包含复选框ASP.Net Core MVC的“编辑”操作？

我有两个表“ Project”和“ Offices”，我想实现“多对多”关系，从而产生“ ProjectManagement”表。

我想在创建项目时定义负责办公室，我执行了create动作，但是[HttpPost] edit动作出现问题，我通过删除“ ProjectManagement”表中所有与之相关的先前记录来解决此问题使用当前编辑的项目，然后重新保存新的编辑，但效果不太好。

Project.cs

public class Project 
    {
        public int Id { get; set; } 
        public string ProjectCode { get; set; } 
        public string Donor { get; set; } 
        public DateTime StartDate { get; set; } 
        public DateTime EndtDate { get; set; }
        
    }

Office.cs

public class Office 
    {
        public int Id { get; set; } 
        public int RegionId { get; set; }
        public string OfficeName { get; set; }
        public string OfficeAddress { get; set; }
        public string Latitude_y { get; set; }
        public string Longitude_x { get; set; }
        public virtual Region Region { get; set; }
        public bool Selected { get; set; }

    }

ProjectManagement.cs

public class ProjectManagement 
    {
        public int Id { get; set; }
        public int ProjectId { get; set; }
        public int OfficeId { get; set; }
        public virtual Project Project { get; set; }
        public virtual Office Office { get; set; }
    }

ProjectViewModel.cs

public class ProjectViewModel
    {
        public int Id { get; set; }
        public string ProjectCode { get; set; }
        public string Donor { get; set; }
        public DateTime StartDate { get; set; } 
        public DateTime EndtDate { get; set; }
        public string Notes { get; set; }
        public IList<SelectListItem> Offices { get; set; }
        
    }

// GET：项目/创建

public IActionResult Create()
{
    var offices = _office.Entity.GetAll();
    
    var item = offices.Select(x => new SelectListItem()
    {
        Text = x.OfficeName,Value = x.Id.ToString()
    }).ToList();

    var projectVM = new ProjectViewModel()
    {
        Offices = item
        
    };
    return View(projectVM);
}

// POST：项目/创建

[HttpPost]
[ValidateAntiForgeryToken]
public IActionResult Create(ProjectViewModel model)
{
    if (ModelState.IsValid)
    {
        Project project = new Project
        {
            ProjectCode = model.ProjectCode,Donor = model.Donor,StartDate = model.StartDate,EndtDate = model.EndtDate

        };
        _project.Entity.Insert(project);
        _project.Save();

       var officeIds = model.Offices.Where(x => x.Selected).Select(y => y.Value);
        foreach (var id in officeIds)
        {
            ProjectManagement pm = new ProjectManagement
            {
                OfficeId = int.Parse(id),ProjectId = project.Id
            };
            _projectManagement.Entity.Insert(pm);
            _projectManagement.Save();
        } 

        return RedirectToAction(nameof(Index));
    }

    return View(model);
}

// GET：Project / Edit / 5

        public IActionResult Edit(int? id)
        {
            if (id == null)
            {
                return NotFound();
            }

            var project = _project.Entity.GetById(id);
            if (project == null)
            {
                return NotFound();
            }

  var selectedoffices = _projectManagement.Entity.GetAll().Where(a => a.ProjectId == id);
            var offices = _office.Entity.GetAll();
                            
            foreach (var i in selectedoffices)
            {
                i.Office.Selected = true;
            }

            var item = offices.Select(x => new SelectListItem()
            {
                Text = x.OfficeName,Value = x.Id.ToString(),Selected = x.Selected
            }).ToList();

            

            ProjectViewModel projectViewModel = new ProjectViewModel
            {
                Id = project.Id,ProjectCode = project.ProjectCode,Donor = project.Donor,StartDate = project.StartDate,EndtDate = project.EndtDate,Offices = item
            };
            return View(projectViewModel);
        }

// POST：Project / Edit / 5

[HttpPost]
[ValidateAntiForgeryToken]
public IActionResult Edit(int id,ProjectViewModel model)
{
    if (id != model.Id)
    {
        return NotFound();
    }

    if (ModelState.IsValid)
    {
        try
        {

            Project project = new Project
            {
                Id = model.Id,ProjectCode = model.ProjectCode,EndtDate = model.EndtDate
            };

            _project.Entity.Update(project);
            _project.Save();
        }

        catch (DbUpdateConcurrencyException)
        {
            if (!ProjectExists(model.Id))
            {
                return NotFound();
            }
            else
            {
                throw;
            }
        }
        var officeIds = model.Offices.Where(x => x.Selected).Select(y => y.Value);
        var existingoffices = _projectManagement.Entity.GetAll().Where(x => x.ProjectId == id).ToList();
        foreach (var item in existingoffices)
        {
            _projectManagement.Entity.Delete(item.Id);
            _projectManagement.Save();
        }

        foreach (var i in officeIds)
        {

            ProjectManagement pm = new ProjectManagement
            {
                OfficeId = int.Parse(i),ProjectId = id
            };
            _projectManagement.Entity.Insert(pm);
            _projectManagement.Save();

        }

        return RedirectToAction(nameof(Index));

    }
    return View(model);
}

编辑视图：

<div class="form-group">
                @for (int i = 0; i < Model.Offices.Count; i++)
                {

                    <input type="hidden" asp-for="@Model.Offices[i].Value" />
                    <input asp-for="Offices[i].Selected" />@Model.Offices[i].Text
                }
            </div>