现在我的ViewModel看起来像这样：
public class MyViewModel
{
private readonly IMyService myService;
public ClaimantSearchViewModel(IMyService myService)
{
this.myService = myService;
}
}
消费此Controller的{{1}}如下所示：
ViewModel我需要的是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);
}
}
看起来像这样：
Controller现在，调用第一个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);
}
}
方法可以正常工作（使用
Index在我的builder.RegisterSource(new AnyConcreteTypeNotAlreadyRegisteredSource(x => x.Name.Contains("ViewModel")));
中，但Startup class到POST会给你一个Index(MyViewModel model)例外。我意识到可以使用我No parameterless constructor defined for this object的{{1}}将是最有可能的解决方案......但我无法找到任何有关如何开始使用的帮助。请帮助我，尤其是custom model binder中的DI。
答案 0 :(得分：4)
我们在这里得到了答案：https://github.com/aspnet/Mvc/issues/4167
答案是使用：[FromServices]
我的模特最终看起来像这样：
public class MyViewModel
{
[FromServices]
public IMyService myService { get; set; }
public ClaimantSearchViewModel(IMyService myService)
{
this.myService = myService;
}
}
虽然它的悲伤，使该属性public，它是不必使用悲伤更不用说custom model binder。
另外，据说你应该能够在Action方法中将[FromServices]作为param的一部分传递，它确实解析了类，但是它破坏了模型绑定...即我的属性都没有被映射。它看起来像这样:(但是，这不工作所以使用上面的例子）
public class MyController : Controller
{
... same as in OP
[HttpPost]
public IActionResult Index([FromServices]MyViewModel model)
{
return View(model);
}
}
更新1
使用[FromServices]属性后，我们决定在所有ViewModels中注入属性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。所以我们决定删除[FromServices]属性并使我们的自定义模型绑定器工作：
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);
}
}
它是在Startup ConfigureServices方法中注册的：
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();。）
更新2 经过各种迭代让它工作（使用帮助https://github.com/aspnet/Mvc/issues/4196），这是最终的结果：
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;
}
}
您显然希望将OUR.SOLUTION...替换为您namespace的{{1}}注册：
ViewModels答案 1 :(得分：0)
这个问题被标记为 ASP.NET Core，所以这是我们针对 dotnet core 3.1 的解决方案。
我们的解决方案概要：TheProject 需要使 ICustomerService 可用于在请求管道中自动创建的对象。需要它的类用接口 IUsesCustomerService 标记。 Binder在创建对象时会检查这个接口，并处理特殊情况。
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());
});
}