使用视图模型类插入数据

如何解决使用视图模型类插入数据

模型类：：

public class MappedModels
    {
        [Key]
        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public int MappedId { get; set; }
        public int MappedType { get; set; }
        public decimal MappedAmount { get; set; }
        
        [ForeignKey("ProjectId")]
        public ProjectModels Project { get; set; } 
        public int ProjectId { get; set; }
    }

查看模型类：：

public class MappedViewModels
    {
        public int MappedType { get; set; }
        public decimal MappedAmount { get; set; }
        public int ProjectId { get; set; }
        public string ProjectName { get; set; }
        
        // these two fields only in MappedViewModels for calculation purpose
        public decimal ProjectAllocatedAmount { get; set; } 
        public decimal RemainingAmount { get; set; }  
}

我已经使用MappedViewModels为Create.cshtml创建了MappedModels页面。现在，当我尝试提交表单时，出现错误：:

The model item passed into the dictionary is of type 'myapp.Models.MappedModels',but this dictionary requires a model item of type 'myapp.ViewModels.MappedViewModels'.

我的创建控制器方法：：

[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult Create([Bind(Include = "MappedId,MappedType,MappedAmount,ProjectId")] MappedModels mappedModels)
{
    if (ModelState.IsValid)
    {
        db.Mappeds.Add(mappedModels);
        db.SaveChanges();
        return RedirectToAction("Index");
    }
    return View(mappedModels);
}

如果我将方法更改为public ActionResult Create( MappedViewModels mappedModels)，则在db.Mappeds.Add(mappedModels)中出现错误

我必须使用MappedViewModels中public ActionResult Create(int? ProjectId)的字段。

此外，我的MappedViewModels不包含属性MappedId，如果我将其保留在（MappedViewModels）中，那么MappedId怎么可以自动递增。>

那么如何使用MappedViewModels到MappedModels插入数据？

根据解决方案的建议，我尝试了::

public ActionResult Create([Bind(Include = "MappedType,ProjectId")] MappedViewModels model)
{
    if (ModelState.IsValid)
    {
        var dbMappedModel = new MappedModels
        {
          MappedType = model.MappedType,MappedAmount = model.MappedAmount,ProjectId = model.ProjectId
        }

        db.Mappeds.Add(dbMappedModel);
        db.SaveChanges();
        return RedirectToAction("Index");
    }
    return View(mappedModels);
}

但是出现错误Validation failed for one or more entities. See 'EntityValidationErrors' property for more details.。这是由于存在多个必填字段的Project类引起的。请帮忙！！！

解决方法

如下更新您的操作逻辑

[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult Create([Bind(Include = "MappedType,MappedAmount,ProjectId")] MappedViewModels model)
{
    if (ModelState.IsValid)
    {
        // when you add to the context,create a new MappedModels object
        // You need not to worry about the MappedId,it will be auto incremented
        var dbMappedModel = new MappedModels
        {
          MappedType = model.MappedType,MappedAmount = = model.MappedAmount,Project = new ProjectModels { ... }
        }

        db.Mappeds.Add(dbMappedModel);
        db.SaveChanges();
        return RedirectToAction("Index");
    }
    return View(mappedModels);
}

[Bind(Include = "MappedType,ProjectId")]的用途是什么，我认为这不是必需的。我没用过。