Asp.net mvc 使用Autofac将服务注入基类

TL；DR:当两个自定义

ModelBinder

实现都依赖Autofac向它们注入（公共）依赖项时，如何将它们共享的逻辑整合到一个基类中

---

在查看我正在处理的ASP.NETMVC项目中的一些代码时，我意识到我有两个自定义模型绑定器，它们基本上做相同的事情。它们都继承自

DefaultModelBinder

，并且都使用注入其构造函数的

IEncodingService

对两个独立视图模型类上的单个属性进行编码

public class ResetQuestionAndAnswerViewModelBinder : DefaultModelBinder {
    public ResetQuestionAndAnswerViewModelBinder(IEncodingService encodingService) {
        encoder = encodingService;
    }

    private readonly IEncodingService encoder;

    public override object BindModel(ControllerContext controllerContext,
                                     ModelBindingContext bindingContext) {
        var model = base.BindModel(controllerContext, bindingContext) as ResetQuestionAndAnswerViewModel;

        if (model != null) {
            var answer = bindingContext.ValueProvider.GetValue("Answer");

            if ((answer != null) && !(answer.AttemptedValue.IsNullOrEmpty())) {
                model.Answer = encoder.Encode(answer.AttemptedValue);
            }
        }

        return model;
    }
}

public class ConfirmIdentityViewModelBinder : DefaultModelBinder {
    public ConfirmIdentityViewModelBinder(IEncodingService encodingService) {
        encoder = encodingService;
    }

    private readonly IEncodingService encoder;

    public override object BindModel(ControllerContext controllerContext,
                                     ModelBindingContext bindingContext) {
        var model = base.BindModel(controllerContext, bindingContext) as ConfirmIdentityViewModel;

        if (model != null) {
            var secretKey = bindingContext.ValueProvider.GetValue("SecretKey");

            if ((secretKey != null) && !(secretKey.AttemptedValue.IsNullOrEmpty())) {
                model.SecretKeyHash = encoder.Encode(secretKey.AttemptedValue);
            }
        }

        return model;
    }
}

我为这两个类编写了一个要从中继承的通用基类：

public class EncodedPropertyModelBinder<TViewModel> : DefaultModelBinder 
    where TViewModel : class {

    public EncodedPropertyModelBinder(IEncodingService encodingService,
                                      string propertyName) {
        encoder = encodingService;
        property = propertyName;
    }

    private readonly IEncodingService encoder;
    private readonly string property;

    public override object BindModel(ControllerContext controllerContext,
                                     ModelBindingContext bindingContext) {
        var model = base.BindModel(controllerContext, bindingContext) as TViewModel;

        if (model != null) {
            var value = bindingContext.ValueProvider.GetValue(property);

            if ((value != null) && !(value.AttemptedValue.IsNullOrEmpty())) {
                var encodedValue = encoder.Encode(value.AttemptedValue);

                var propertyInfo = model.GetType().GetProperty(property);
                propertyInfo.SetValue(model, encodedValue, null);
            }
        }

        return model;
    }
}

公共类EncodedPropertyModelBinder:DefaultModelBinder
TViewModel:类的位置{
公共编码属性模型绑定器（IceodingService encodingService，
字符串属性名称）{
编码器=编码服务；
property=propertyName；
}
专用只读编码服务编码器；
私有只读字符串属性；
公共覆盖对象绑定模型（ControllerContext ControllerContext，
ModelBindingContext（绑定上下文）{
var model=base.BindModel（controllerContext，bindingContext）作为TViewModel；
如果（型号！=null）{
var value=bindingContext.ValueProvider.GetValue（属性）；
if（（value！=null）&&&！（value.AttemptedValue.IsNullOrEmpty（））{
var encodedValue=encoder.Encode（value.AttemptedValue）；
var propertyInfo=model.GetType（）.GetProperty（属性）；
propertyInfo.SetValue（model，encodedValue，null）；
}
}
收益模型；
}
}

---

使用Autofac，我如何将

IEncodingService

注入基类构造函数，同时强制派生类提供要编码的属性的名称？

实际上，我的做法略有不同。这意味着我将封装属性操作的细节，并将不同的实现传递给单个模型绑定器

首先，定义一个表示绑定单个属性的接口：

public interface IPropertyBinder
{
    void SetPropertyValue(object model, ModelBindingContext context);
}

然后，使用最初来自

encodedpropertypodelbinder

的参数实现它：

public sealed class PropertyBinder : IPropertyBinder
{
    private readonly IEncodingService _encodingService;
    private readonly string _propertyName;

    public PropertyBinder(IEncodingService encodingService, string propertyName)
    {
        _encodingService = encodingService;
        _propertyName = propertyName;
    }

    public void SetPropertyValue(object model, ModelBindingContext bindingContext)
    {
        var value = bindingContext.ValueProvider.GetValue(_propertyName);

        if(value != null && !value.AttemptedValue.IsNullOrEmpty())
        {
            var encodedValue = _encodingService.Encode(value.AttemptedValue);

            var property = model.GetType().GetProperty(_propertyName);

            property.SetValue(model, encodedValue, null);
        }
    }
}

builder.
    Register(c => new EncodedPropertyModelBinder(new PropertyBinder(c.Resolve<IEncodingService>(), "Answer")))
    .Named<EncodedPropertyModelBinder>("AnswerBinder");

builder.
    Register(c => new EncodedPropertyModelBinder(new PropertyBinder(c.Resolve<IEncodingService>(), "SecretKey")))
    .Named<EncodedPropertyModelBinder>("SecretKeyBinder");

接下来，使用新接口实现

encodedpropertypodelbinder

：

public class EncodedPropertyModelBinder : DefaultModelBinder
{
    private readonly IPropertyBinder _propertyBinder;

    public EncodedPropertyModelBinder(IPropertyBinder propertyBinder)
    {
        _propertyBinder = propertyBinder;
    }

    public override object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
    {
        var model = base.BindModel(controllerContext, bindingContext);

        if(model != null)
        {
            _propertyBinder.SetPropertyValue(model, bindingContext);
        }

        return model;
    }
}

最后，使用Autofac命名实例注册视图模型的两个版本，传入不同的

PropertyBinder

配置：

public sealed class PropertyBinder : IPropertyBinder
{
    private readonly IEncodingService _encodingService;
    private readonly string _propertyName;

    public PropertyBinder(IEncodingService encodingService, string propertyName)
    {
        _encodingService = encodingService;
        _propertyName = propertyName;
    }

    public void SetPropertyValue(object model, ModelBindingContext bindingContext)
    {
        var value = bindingContext.ValueProvider.GetValue(_propertyName);

        if(value != null && !value.AttemptedValue.IsNullOrEmpty())
        {
            var encodedValue = _encodingService.Encode(value.AttemptedValue);

            var property = model.GetType().GetProperty(_propertyName);

            property.SetValue(model, encodedValue, null);
        }
    }
}

builder.
    Register(c => new EncodedPropertyModelBinder(new PropertyBinder(c.Resolve<IEncodingService>(), "Answer")))
    .Named<EncodedPropertyModelBinder>("AnswerBinder");

builder.
    Register(c => new EncodedPropertyModelBinder(new PropertyBinder(c.Resolve<IEncodingService>(), "SecretKey")))
    .Named<EncodedPropertyModelBinder>("SecretKeyBinder");

builder。
寄存器（c=>newencodedpropertypodelbinder（newpropertybinder（c.Resolve（），“Answer”））
.命名为（“AnswerBinder”）；
建设者
寄存器（c=>newencodedpropertypodelbinder（newpropertybinder（c.Resolve（），“SecretKey”））
.命名为（“SecretKeyBinder”）；