C# 抽象模型的Asp.NETCore2.0（MVC）内容绑定器

我刚刚开始用MVC框架开发ASP.Net Core 2.0

当从查看页面发布（表单提交）数据时，我遇到了一些问题

以下是我的观点：

<form action="/Media/CreateVideo" method="post">
                <input type="text" name="Name" />
                <input type="hidden" name="ModelType" value="VideoModel" />
                <input type="text" name="ContentType" value="video" />

                <button type="submit">Yes</button>
  </form>

    public abstract class ContentModel
    {
        [Key]
        public int Id { get; set; }
        [Required]
        public string Name { get; set; }
        [Required]
        public string ContentType { get; set; }
        public string Data { get; set; }

        public virtual FolderModel ParentFolder { get; set; }
    }



    public abstract class FileModel : ContentModel
    {
        public string Path { get; set; }
    }

    public class VideoModel : FileModel
    {
        //Other properties i.e. video duration, size, format etc.
    }

    public class ImageModel : FileModel
    {
        //Other properties i.e. size, format, cropping value, hue, etc.
    }

        [HttpPost]
        public IActionResult CreateWeb([ModelBinder(BinderType = typeof(CustomModelBinder))]ContentModel item)
        {
            _contentService.Add(item);
            _contentService.SaveChanges();

            return View();
        }

public class CustomModelBinder : IModelBinder
    {

        public Task BindModelAsync(ModelBindingContext bindingContext)
        {
            if (bindingContext == null)
                throw new ArgumentNullException(nameof(bindingContext));

            ValueProviderResult values = bindingContext.ValueProvider.GetValue("ModelType");
            if (values.Length == 0)
                return Task.CompletedTask;

            string typeString = values.FirstValue;
            Type type = Type.GetType(
                "Magic.Core.Models." + typeString + ", Magic.Core.Models",
                true
            );

            object model = Activator.CreateInstance(type);

            var metadataProvider = (IModelMetadataProvider)bindingContext.HttpContext.RequestServices.GetService(typeof(IModelMetadataProvider));
            bindingContext.ModelMetadata = metadataProvider.GetMetadataForType(type);
            bindingContext.Result = ModelBindingResult.Success(model);

            return Task.CompletedTask;
        }
    }

我的控制器：

<form action="/Media/CreateVideo" method="post">
                <input type="text" name="Name" />
                <input type="hidden" name="ModelType" value="VideoModel" />
                <input type="text" name="ContentType" value="video" />

                <button type="submit">Yes</button>
  </form>

    public abstract class ContentModel
    {
        [Key]
        public int Id { get; set; }
        [Required]
        public string Name { get; set; }
        [Required]
        public string ContentType { get; set; }
        public string Data { get; set; }

        public virtual FolderModel ParentFolder { get; set; }
    }



    public abstract class FileModel : ContentModel
    {
        public string Path { get; set; }
    }

    public class VideoModel : FileModel
    {
        //Other properties i.e. video duration, size, format etc.
    }

    public class ImageModel : FileModel
    {
        //Other properties i.e. size, format, cropping value, hue, etc.
    }

        [HttpPost]
        public IActionResult CreateWeb([ModelBinder(BinderType = typeof(CustomModelBinder))]ContentModel item)
        {
            _contentService.Add(item);
            _contentService.SaveChanges();

            return View();
        }

public class CustomModelBinder : IModelBinder
    {

        public Task BindModelAsync(ModelBindingContext bindingContext)
        {
            if (bindingContext == null)
                throw new ArgumentNullException(nameof(bindingContext));

            ValueProviderResult values = bindingContext.ValueProvider.GetValue("ModelType");
            if (values.Length == 0)
                return Task.CompletedTask;

            string typeString = values.FirstValue;
            Type type = Type.GetType(
                "Magic.Core.Models." + typeString + ", Magic.Core.Models",
                true
            );

            object model = Activator.CreateInstance(type);

            var metadataProvider = (IModelMetadataProvider)bindingContext.HttpContext.RequestServices.GetService(typeof(IModelMetadataProvider));
            bindingContext.ModelMetadata = metadataProvider.GetMetadataForType(type);
            bindingContext.Result = ModelBindingResult.Success(model);

            return Task.CompletedTask;
        }
    }

我的自定义模型活页夹类：

<form action="/Media/CreateVideo" method="post">
                <input type="text" name="Name" />
                <input type="hidden" name="ModelType" value="VideoModel" />
                <input type="text" name="ContentType" value="video" />

                <button type="submit">Yes</button>
  </form>

    public abstract class ContentModel
    {
        [Key]
        public int Id { get; set; }
        [Required]
        public string Name { get; set; }
        [Required]
        public string ContentType { get; set; }
        public string Data { get; set; }

        public virtual FolderModel ParentFolder { get; set; }
    }



    public abstract class FileModel : ContentModel
    {
        public string Path { get; set; }
    }

    public class VideoModel : FileModel
    {
        //Other properties i.e. video duration, size, format etc.
    }

    public class ImageModel : FileModel
    {
        //Other properties i.e. size, format, cropping value, hue, etc.
    }

        [HttpPost]
        public IActionResult CreateWeb([ModelBinder(BinderType = typeof(CustomModelBinder))]ContentModel item)
        {
            _contentService.Add(item);
            _contentService.SaveChanges();

            return View();
        }

public class CustomModelBinder : IModelBinder
    {

        public Task BindModelAsync(ModelBindingContext bindingContext)
        {
            if (bindingContext == null)
                throw new ArgumentNullException(nameof(bindingContext));

            ValueProviderResult values = bindingContext.ValueProvider.GetValue("ModelType");
            if (values.Length == 0)
                return Task.CompletedTask;

            string typeString = values.FirstValue;
            Type type = Type.GetType(
                "Magic.Core.Models." + typeString + ", Magic.Core.Models",
                true
            );

            object model = Activator.CreateInstance(type);

            var metadataProvider = (IModelMetadataProvider)bindingContext.HttpContext.RequestServices.GetService(typeof(IModelMetadataProvider));
            bindingContext.ModelMetadata = metadataProvider.GetMetadataForType(type);
            bindingContext.Result = ModelBindingResult.Success(model);

            return Task.CompletedTask;
        }
    }

下面是发生的情况

我能够告诉控制器，这个内容模型是视频模型。 但是，所有post值（如名称、ContentType等）均为空

我曾经在MVC5中按照这个线程来做这件事 而且效果很好

---

我的问题是，.Net核心中是否遗漏了一些与模型绑定相关的步骤或有什么新内容？

好吧，我想您的

CustomModelBinder

需要更多的逻辑来从提供者处获取表单值：

public class CustomModelBinder : IModelBinder
{

    public Task BindModelAsync(ModelBindingContext bindingContext)
    {
        if (bindingContext == null)
            throw new ArgumentNullException(nameof(bindingContext));

        ValueProviderResult values = bindingContext.ValueProvider.GetValue("ModelType");
        if (values.Length == 0)
            return Task.CompletedTask;

        string typeString = values.FirstValue;
        Type type = Type.GetType(
            "Magic.Core.Models." + typeString + ", Magic.Core.Models",
            true
        );

        object model = Activator.CreateInstance(type);

        //*get form values from provider
        var content = model as ContentModel;
        if(content != null)
        {
            var provider = bindingContext.ValueProvider;

            var contentType = provider.GetValue("ContentType");
            content.ContentType = contentType != null ? contentType.ToString() : string.Empty;

            var name = provider.GetValue("Name");
            content.Name = name != null ? name.ToString() : string.Empty;
        }
        //*/

        var metadataProvider = (IModelMetadataProvider)bindingContext.HttpContext.RequestServices.GetService(typeof(IModelMetadataProvider));
        bindingContext.ModelMetadata = metadataProvider.GetMetadataForType(type);
        bindingContext.Result = ModelBindingResult.Success(model);

        return Task.CompletedTask;
    }
}

---

我仍然想知道为什么我必须自己绑定post数据。但在MVC5中，它会自动为我做这件事吗？@DemonEden，你可能在回忆ASP NET（无核心）MVC的

DefaultModelBinder

？是的，DefaultModelBinder及其CreateModel方法。但现在，我最终做了类似于PropertyInfo[]infoList=type.GetProperties（）的事情；var provider=bindingContext.ValueProvider；foreach（PropertyInfo info in infoList）{var val=provider.GetValue（info.Name）.FirstValue；info.SetValue（model，val，null）；}由于对性能的影响，需要考虑使用反射。