MVC 6自定义模型绑定器的依赖注入
MVC 6自定义模型绑定器的依赖注入
提问于 2016-02-25 00:34:44
现在我的ViewModel看起来是这样的：
public class MyViewModel
{
private readonly IMyService myService;
public ClaimantSearchViewModel(IMyService myService)
{
this.myService = myService;
}
}使用此Controller的ViewModel如下所示：
public class MyController : Controller
{
private readonly IMyService myService;
public HomeController(IMyService myService)
{
this.myService = myService;
}
public IActionResult Index()
{
var model = new MyViewModel(myService);
return View(model);
}
[HttpPost]
public async Task<IActionResult> Find()
{
var model = new MyViewModel(myService);
await TryUpdateModelAsync(model);
return View("Index", model);
}
}我需要的是我的Controller看起来是这样的：
public class MyController : Controller
{
private readonly IServiceProvider servicePovider;
public MyController(IServiceProvider servicePovider)
{
this.servicePovider = servicePovider;
}
public IActionResult Index()
{
var model = servicePovider.GetService(typeof(MyViewModel));
return View(model);
}
[HttpPost]
public IActionResult Index(MyViewModel model)
{
return View(model);
}
}现在，调用第一个Index方法很好(使用
builder.RegisterSource(new AnyConcreteTypeNotAlreadyRegisteredSource(x => x.Name.Contains("ViewModel")));在我的Startup class中)，但是执行POST到Index(MyViewModel model)的操作会给您一个No parameterless constructor defined for this object异常。我意识到可以使用我的custom model binder的DI将是最有可能的解决方案.但我找不到任何关于如何开始这里的帮助。请帮助我，特别是Autofac in MVC 6。
回答 2
Stack Overflow用户
回答已采纳
发布于 2016-02-26 20:17:30
我们在这里得到了答案：https://github.com/aspnet/Mvc/issues/4167
答案是使用: FromServices
我的模特最后看起来是这样：
public class MyViewModel
{
[FromServices]
public IMyService myService { get; set; }
public ClaimantSearchViewModel(IMyService myService)
{
this.myService = myService;
}
}虽然让这个属性成为public是很悲哀的，但它比不得不使用custom model binder要少得多。
此外，假定您应该能够在Action方法中将[FromServices]作为param的一部分传递，它确实解析了类，但这破坏了模型绑定.我所有的财产都没有被映射。它看起来是这样的：(但同样，-它不能工作，所以请使用上面的例子)
public class MyController : Controller
{
... same as in OP
[HttpPost]
public IActionResult Index([FromServices]MyViewModel model)
{
return View(model);
}
}更新1
在使用[FromServices]属性之后，我们决定在所有ViewModels中注入属性并不是我们想要的方式，特别是在考虑使用测试进行长期维护时。因此，我们决定删除[FromServices]属性，并使我们的自定义模型绑定器正常工作：
public class IoCModelBinder : IModelBinder
{
public Task<ModelBindingResult> BindModelAsync(ModelBindingContext bindingContext)
{
var serviceProvider = bindingContext.OperationBindingContext.HttpContext.RequestServices;
var model = serviceProvider.GetService(bindingContext.ModelType);
bindingContext.Model = model;
var binder = new GenericModelBinder();
return binder.BindModelAsync(bindingContext);
}
}它像这样在Startup ConfigureServices方法中注册：
services.AddMvc().AddMvcOptions(options =>
{
options.ModelBinders.Clear();
options.ModelBinders.Add(new IoCModelBinder());
});就是这样。(甚至不确定是否需要options.ModelBinders.Clear();。)
UPDATE 2在经过多次迭代以使其正常工作(使用帮助https://github.com/aspnet/Mvc/issues/4196)之后，最后的结果如下：
public class IoCModelBinder : IModelBinder
{
public async Task<ModelBindingResult> BindModelAsync(ModelBindingContext bindingContext)
{ // For reference: https://github.com/aspnet/Mvc/issues/4196
if (bindingContext == null)
throw new ArgumentNullException(nameof(bindingContext));
if (bindingContext.Model == null && // This binder only constructs viewmodels, avoid infinite recursion.
(
(bindingContext.ModelType.Namespace.StartsWith("OUR.SOLUTION.Web.ViewModels") && bindingContext.ModelType.IsClass)
||
(bindingContext.ModelType.IsInterface)
)
)
{
var serviceProvider = bindingContext.OperationBindingContext.HttpContext.RequestServices;
var model = serviceProvider.GetRequiredService(bindingContext.ModelType);
// Call model binding recursively to set properties
bindingContext.Model = model;
var result = await bindingContext.OperationBindingContext.ModelBinder.BindModelAsync(bindingContext);
bindingContext.ValidationState[model] = new ValidationStateEntry() { SuppressValidation = true };
return result;
}
return await ModelBindingResult.NoResultAsync;
}
}很明显，您想要用OUR.SOLUTION...替换为您的ViewModels的任何namespace，我们的注册：
services.AddMvc().AddMvcOptions(options =>
{
options.ModelBinders.Insert(0, new IoCModelBinder());
});更新3：这是Model Binder及其Provider与ASP.NET Core 2.X一起工作的最新迭代。
public class IocModelBinder : ComplexTypeModelBinder
{
public IocModelBinder(IDictionary<ModelMetadata, IModelBinder> propertyBinders, ILoggerFactory loggerFactory) : base(propertyBinders, loggerFactory)
{
}
protected override object CreateModel(ModelBindingContext bindingContext)
{
object model = bindingContext.HttpContext.RequestServices.GetService(bindingContext.ModelType) ?? base.CreateModel(bindingContext);
if (bindingContext.HttpContext.Request.Method == "GET")
bindingContext.ValidationState[model] = new ValidationStateEntry { SuppressValidation = true };
return model;
}
}
public class IocModelBinderProvider : IModelBinderProvider
{
private readonly ILoggerFactory loggerFactory;
public IocModelBinderProvider(ILoggerFactory loggerFactory)
{
this.loggerFactory = loggerFactory;
}
public IModelBinder GetBinder(ModelBinderProviderContext context)
{
if (context == null)
{
throw new ArgumentNullException(nameof(context));
}
if (!context.Metadata.IsComplexType || context.Metadata.IsCollectionType) return null;
var propertyBinders = new Dictionary<ModelMetadata, IModelBinder>();
foreach (ModelMetadata property in context.Metadata.Properties)
{
propertyBinders.Add(property, context.CreateBinder(property));
}
return new IocModelBinder(propertyBinders, loggerFactory);
}
}然后在Startup
services.AddMvc(options =>
{
// add IoC model binder.
IModelBinderProvider complexBinder = options.ModelBinderProviders.FirstOrDefault(x => x.GetType() == typeof(ComplexTypeModelBinderProvider));
int complexBinderIndex = options.ModelBinderProviders.IndexOf(complexBinder);
options.ModelBinderProviders.RemoveAt(complexBinderIndex);
options.ModelBinderProviders.Insert(complexBinderIndex, new IocModelBinderProvider(loggerFactory));Stack Overflow用户
发布于 2021-02-05 00:33:04
这个问题被标记为ASP.NET核心，下面是我们针对DOTNetCore3.1的解决方案。
我们的解决方案概要: TheProject需要将ICustomerService提供给在请求管道中自动创建的对象。需要这样做的类被标记为一个接口IUsesCustomerService。然后由Binder在创建对象时检查这个接口，并处理特例。
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc.ModelBinding;
using Microsoft.Extensions.Logging;
namespace TheProject.Infrastructure.DependencyInjection
{
/// <summary>
/// This is a simple pass through class to the binder class.
/// It gathers some information from the context and passes it along.
/// </summary>
public class TheProjectModelBinderProvider : IModelBinderProvider
{
public TheProjectModelBinderProvider()
{
}
public IModelBinder GetBinder(ModelBinderProviderContext context)
{
ILoggerFactory ilogger;
if (context == null)
{
throw new ArgumentNullException(nameof(context));
}
// The Binder that gets returned is a <ComplexTypeModelBinder>, but I'm
// not sure what side effects returning early here might cause.
if (!context.Metadata.IsComplexType || context.Metadata.IsCollectionType)
{
return null;
}
var propertyBinders = new Dictionary<ModelMetadata, IModelBinder>();
foreach (ModelMetadata property in context.Metadata.Properties)
{
propertyBinders.Add(property, context.CreateBinder(property));
}
ilogger = (ILoggerFactory)context.Services.GetService(typeof(ILoggerFactory));
return new TheProjectModelBinder(propertyBinders, ilogger);
}
}
/// <summary>
/// Custom model binder.
/// Allows interception of endpoint method to adjust object construction
/// (allows automatically setting properties on an object that ASP.NET creates for the endpoint).
/// Here this is used to make sure the <see cref="ICustomerService"/> is set correctly.
/// </summary>
public class TheProjectModelBinder : ComplexTypeModelBinder
{
public TheProjectModelBinder(IDictionary<ModelMetadata, IModelBinder> propertyBinders, ILoggerFactory loggerFactory)
: base(propertyBinders, loggerFactory)
{
}
/// <summary>
/// Method to construct an object. This normally calls the default constructor.
/// This method does not set property values, setting those are handled elsewhere in the pipeline,
/// with the exception of any special properties handled here.
/// </summary>
/// <param name="bindingContext">Context.</param>
/// <returns>Newly created object.</returns>
protected override object CreateModel(ModelBindingContext bindingContext)
{
if (bindingContext == null)
throw new ArgumentNullException(nameof(bindingContext));
var customerService = (ICustomerService)bindingContext.HttpContext.RequestServices.GetService(typeof(ICustomerService));
bool setcustomerService = false;
object model;
if (typeof(IUsesCustomerService).IsAssignableFrom(bindingContext.ModelType))
{
setcustomerService = true;
}
// I think you can also just call Activator.CreateInstance here.
// The end result is an object that's constructed, but no properties are set yet.
model = base.CreateModel(bindingContext);
if (setcustomerService)
{
((IUsesCustomerService)model).SetcustomerService(customerService);
}
return model;
}
}
}然后，在启动代码中，确保设置AddMvcOptions。
public void ConfigureServices(IServiceCollection services)
{
// ...
// asp.net core 3.1 MVC setup
services.AddControllersWithViews()
.AddApplicationPart(assembly)
.AddRazorRuntimeCompilation()
.AddMvcOptions(options =>
{
IModelBinderProvider complexBinder = options.ModelBinderProviders.FirstOrDefault(x => x.GetType() == typeof(ComplexTypeModelBinderProvider));
int complexBinderIndex = options.ModelBinderProviders.IndexOf(complexBinder);
options.ModelBinderProviders.RemoveAt(complexBinderIndex);
options.ModelBinderProviders.Insert(complexBinderIndex, new Infrastructure.DependencyInjection.TheProjectModelBinderProvider());
});
}页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/35616035
复制相关文章
相似问题
腾讯云开发者
