在ASP.net MVC内核中替换DefaultModelBinder

Question

我正在将一个MVC5项目转换为核心。我目前有一个自定义模型绑定器，我将其用作我的nhibernate实体模型绑定器。我可以选择获取和绑定，方法是从数据库中获取实体，然后调用基本DefaultModelBinder将修改后的数据从请求绑定到实体中。

现在我正在尝试实现IModelBinder...我可以很好地获取实体。但是，当我不再需要调用基本DefaultModelBinder时，如何调用“默认模型绑定器”来绑定其余的表单数据呢？

提前感谢！

Answer 1

你可以这样做：

using System;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc.ModelBinding;
using Microsoft.AspNetCore.Mvc.ModelBinding.Binders;
using Microsoft.Extensions.DependencyInjection;
using Newtonsoft.Json;

namespace Media.Onsite.Api.Middleware.ModelBindings
{
    public class Startup
    {
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddMvc(options =>
            {
                // add the custom binder at the top of the collection
                options.ModelBinderProviders.Insert(0, new MyCustomModelBinderProvider());
            });
        }
    }

    public class MyCustomModelBinderProvider : IModelBinderProvider
    {
        public IModelBinder GetBinder(ModelBinderProviderContext context)
        {
            if (context.Metadata.ModelType == typeof(MyType))
            {
                return new BinderTypeModelBinder(typeof(MyCustomModelBinder));
            }

            return null;
        }
    }

    public class MyCustomModelBinder : IModelBinder
    {
        public Task BindModelAsync(ModelBindingContext bindingContext)
        {
            if (bindingContext == null)
            {
                throw new ArgumentNullException(nameof(bindingContext));
            }

            if (bindingContext.ModelType != typeof(MyType))
            {
                return Task.CompletedTask;
            }

            string modelName = string.IsNullOrEmpty(bindingContext.BinderModelName)
                ? bindingContext.ModelName
                : bindingContext.BinderModelName;

            ValueProviderResult valueProviderResult = bindingContext.ValueProvider.GetValue(modelName);
            if (valueProviderResult == ValueProviderResult.None)
            {
                return Task.CompletedTask;
            }

            bindingContext.ModelState.SetModelValue(modelName, valueProviderResult);

            string valueToBind = valueProviderResult.FirstValue;

            if (valueToBind == null /* or not valid somehow*/)
            {
                return Task.CompletedTask;
            }

            MyType value = ParseMyTypeFromJsonString(valueToBind);

            bindingContext.Result = ModelBindingResult.Success(value);

            return Task.CompletedTask;
        }

        private MyType ParseMyTypeFromJsonString(string valueToParse)
        {
            return new MyType
            {
                // Parse JSON from 'valueToParse' and apply your magic here
            };
        }
    }

    public class MyType
    {
        // Your props here
    }

    public class MyRequestType
    {
        [JsonConverter(typeof(UniversalDateTimeConverter))]
        public MyType PropName { get; set; }

        public string OtherProp { get; set; }
    }
}

Answer 2

我也处于同样的境地。我需要从数据库实例化对象，然后让MVC/Core为我绑定所有属性。经过几个小时的谷歌搜索和“堆栈溢出”，这是我构建的：

public class MyBinder : ComplexTypeModelBinder
{
    public SettingsBinder(IDictionary<ModelMetadata, IModelBinder> propertyBinders) : base(propertyBinders, new LoggerFactory()) { }

    protected override object CreateModel(ModelBindingContext bindingContext)
    {
        return Get_Object_From_Database(); //custom creation logic
    }
}

public class MyBinderProvider : IModelBinderProvider
{
    public IModelBinder GetBinder(ModelBinderProviderContext context)
    {
        //make sure I use it with my type only
        if (context.Metadata.ModelType == typeof(My_Object))
        {
            //get property binders for all the stuff
            var propertyBinders = context.Metadata.Properties.ToDictionary(p => p, p => context.CreateBinder(p));

            return new MyBinder(propertyBinders);
        }

        return null;
    }
}

//startup.cs
services.AddMvc(option =>
{
    option.ModelBinderProviders.Insert(0, new MyBinderProvider());
});

ComplexTypeModelBinder被标记为过时，但微软团队在github上表示，这意味着该类型不应由微软内部使用，但它将继续存在。

使用.NET 5测试成功