.Select with EF Core 在视图中返回 ModelError

Question

我想提供一份约会清单以及他们各自的参与者和/或主题。

Planner 模型如下：

public class Planner : BaseEntity
{        
    public int? ProjectCandId { get; set; }
    public int? CandidateId { get; set; }        
    public int? ProjectId { get; set; }
    public int? CustomerId { get; set; }        

    public DateTime PlanDatum { get; set; }
    public string Location { get; set; }        
    public string Description { get; set; }

    public virtual Customer Customer { get; set; }
    public virtual Candidate Candidate { get; set; }
    public virtual Project Project { get; set; }
    public virtual ProjectCand ProjectCand { get; set; }
}

我只需要从客户、项目和候选人中选择数量的字段，所以我创建了一个控制器，如下所示：

 public async Task<IActionResult> Index()
    {
       var afspraken = await _context.Planner
            .Include(c => c.Customer)
            .Include(c => c.Project)
            .Include(c => c.Candidate)
            .Select(s => new { s.Id, s.CandidateId, s.CustomerId, s.Description,  s.IsDeleted, s.Location, s.PlanDatum, 
                s.Customer.CompanyName, 
                s.Project.ProjectTitle, 
                s.Candidate.FullName })
            .ToListAsync().ConfigureAwait(false);
        return View(afspraken);
    }

在我看来我使用@model IEnumerable<MyProject.Models.Planner>。

当不在控制器中应用 .Select-line 时，一切正常，但使用它会产生以下错误：

InvalidOperationException：传递到 ViewDataDictionary 的模型项的类型为 'System.Collections.Generic.List1[<>f__AnonymousType710[System.Int32,System.Nullable1[System.Int32],System.Nullable1[System.Int32],System.String,System .Boolean,System.String,System.DateTime,System.String,System.String,System.String]]'，但是这个 ViewDataDictionary 实例需要一个类型为'System.Collections.Generic.IEnumerable`1[BeagleNoseV3.Models .Planner]'。

我曾尝试创建一个 ViewModel，但这只会使事情变得更加复杂。我想使用 .Select 创建更高效​​的查询，但我被卡住了。

有什么想法吗？

编辑 ViewModel 场景

我已经尝试过 ViewModel 方法，但是我在如何将 VModel 链接到类方面遇到了困难。

我创建了PlannerVM 和PlanVMList：

public class PlannerVM : BaseEntityVM  //BaseEntityVM provides Id, IsDeleted and some other administrative elements
{
    public int? ProjectCandId { get; set; }
    public int? CandidateId { get; set; }
    public int? ProjectId { get; set; }
    public int? CustomerId { get; set; }

    public DateTime PlanDatum { get; set; }
    public string Location { get; set; }        
    public string Description { get; set; }
    public string CandidateFullName { get; set; }
    public string ProjectCode { get; set; }
    public string ProjectTitle { get; set; }
    public string CompanyName { get; set; }
}

public class PlanVMList
{
    public List<PlannerVM> AppointList { get; set; }
}

我未能在 PlannerController 中提供正确的代码来将 ViewModel 链接到我的数据集 afspraken。有什么想法吗？

Answer 1

您的 afspraken 是匿名列表，您正在将其传递给 View，它期望模型类型为 IEnumerable<MyProject.Models.Planner>

将您的最终 Select 语句更改为：

.Select(s => new MyProject.Models.Planner {
...
})

Answer 2

根据您的要求，显示Planner 及其各自的参与者和/或主题。无需指定.Select。

这是一个如下所示的工作演示：

1.型号：

public class BaseEntity
{
    public int Id { get; set; }
    public bool IsDeleted { get; set; }
}
public class Planner : BaseEntity
{
    public int? ProjectCandId { get; set; }
    public int? CandidateId { get; set; }
    public int? ProjectId { get; set; }
    public int? CustomerId { get; set; }

    public DateTime PlanDatum { get; set; }
    public string Location { get; set; }
    public string Description { get; set; }

    public virtual Customer Customer { get; set; }
    public virtual Candidate Candidate { get; set; }
    public virtual Project Project { get; set; }
}  
public class Customer: BaseEntity
{
    public string CompanyName { get; set; }
}
public class Candidate: BaseEntity
{
    public string FullName { get; set; }
}
public class Project: BaseEntity
{
    public string ProjectTitle { get; set; }
}

2.查看：

@model IEnumerable<Planner>
<h1>Index</h1>
<p>
    <a asp-action="Create">Create New</a>
</p>
<table class="table">
    <thead>
        <tr>
            <th>
                @Html.DisplayNameFor(model => model.Id)
            </th>
            <th>
                @Html.DisplayNameFor(model => model.CandidateId)
            </th>
            <th>
                @Html.DisplayNameFor(model => model.CustomerId)
            </th>
            <th>
                @Html.DisplayNameFor(model => model.PlanDatum)
            </th>
            <th>
                @Html.DisplayNameFor(model => model.Location)
            </th>
            <th>
                @Html.DisplayNameFor(model => model.Description)
            </th>
            <th>
                @Html.DisplayNameFor(model => model.Customer)
            </th>
            <th>
                @Html.DisplayNameFor(model => model.Candidate)
            </th>
            <th>
                @Html.DisplayNameFor(model => model.Project)
            </th>
            <th>
                @Html.DisplayNameFor(model => model.IsDeleted)
            </th>
        </tr>
    </thead>
    <tbody>
@foreach (var item in Model) {
        <tr>
            <td>
                @Html.DisplayFor(modelItem => item.Id)
            </td>
            <td>
                @Html.DisplayFor(modelItem => item.CandidateId)
            </td>
            <td>
                @Html.DisplayFor(modelItem => item.CustomerId)
            </td>
            <td>
                @Html.DisplayFor(modelItem => item.PlanDatum)
            </td>
            <td>
                @Html.DisplayFor(modelItem => item.Location)
            </td>
            <td>
                @Html.DisplayFor(modelItem => item.Description)
            </td>
            <td>
                @Html.DisplayFor(modelItem => item.Customer.CompanyName)
            </td>
            <td>
                @Html.DisplayFor(modelItem => item.Candidate.FullName)
            </td>
            <td>
                @Html.DisplayFor(modelItem => item.Project.ProjectTitle)
            </td>
            <td>
                @Html.DisplayFor(modelItem => item.IsDeleted)
            </td>
        </tr>
}
    </tbody>
</table>

3.控制器：

public async Task<IActionResult> Index()
{
    var model = _context.Planner.Include(p => p.Candidate).Include(p => p.Customer).Include(p => p.Project);
    return View(await model.ToListAsync());
}

结果：