Question

我已经找到了几个使用ASP.NET MVC在StructureMap项目中注入自定义模型绑定器的指南，并按照本教程进行了操作：http://benfoster.io/blog/model-binder-dependency-injection-structuremap

我安装了StructureMap.MVC5个包。并在默认注册表中添加了类型绑定：

public class DefaultRegistry : Registry {
    public DefaultRegistry() {
        Scan(scan => {
            scan.Assembly(System.Reflection.Assembly.GetExecutingAssembly());
            scan.WithDefaultConventions();
            scan.With(new ControllerConvention());
        });

        For(typeof(IRepository<>)).Use(typeof(MongoDbRepository<>));

        var dictionary = new ModelBinderMappingDictionary();
        dictionary.Add<Car, CarModelBinder>();

        For<ModelBinderMappingDictionary>().Use(dictionary);
        For<IModelBinderProvider>().Use<StructureMapModelBinderProvider>();
    }
}

public class StructureMapModelBinderProvider : IModelBinderProvider {
    private readonly IContainer container;

    public StructureMapModelBinderProvider(IContainer container) {
        this.container = container;
    }

    public IModelBinder GetBinder(Type modelType) {
        var mappings = container.GetInstance<ModelBinderMappingDictionary>();
        if(mappings != null && mappings.ContainsKey(modelType))
            return container.GetInstance(mappings[modelType]) as IModelBinder;

        return null;
    }
}

现在我得到一个指向该行的NullReferenceException：

var mappings = container.GetInstance<ModelBinderMappingDictionary>();

这些内部异常文本：

在c：\ BuildAgent \ work \ 996e173a8ceccdca \ src \ StructureMap \ SessionCache.cs中的StructureMap.SessionCache.GetDefault（Type pluginType，IPipelineGraph pipelineGraph）：43 C：\ BuildAgent \ work \ 996e173a8ceccdca \ src \ StructureMap \ Container.cs中的StructureMap.Container.GetInstance（Type pluginType）：331 C：\ BuildAgent \ work \ 996e173a8ceccdca \ src \ StructureMap \ Container.cs中的StructureMap.Container.GetInstance（）：201 d：\ projects \ unicorn \ unicorn.web \ infrastructure \ model_binding \ StructuremapModelBinderProvider.cs中的my_project_name.StructureMapModelBinderProvider.GetBinder（Type modelType）：15 System.Web.Mvc.ModelBinderProviderCollection.GetBinder（Type modelType）+57 System.Web.Mvc.ModelBinderDictionary.GetBinder（TypeTypeType，IModelBinder fallbackBinder）+27 System.Web.Mvc.ModelBinderDictionary.GetBinder（Type modelType，Boolean fallbackToDefault）+71 等等...

该代码有什么问题？

Answer 1

看起来您正在尝试将ModelBinder Mapping Dictionary注册为Add方法的返回值，该方法为void。试试这个（默认注册表）：

    var modelBinderMappingDictionary = new ModelBinderMappingDictionary();
    modelBinderMappingDictionary.Add<Car, CarModelBinder>();
    For<ModelBinderMappingDictionary>().Use(modelBinderMappingDictionary);

Answer 2

好的我明白了！

我尝试为StructureMapModelBinderProvider使用另一种生命周期类型：

public class ModelBindingRegistry : Registry {
    public ModelBindingRegistry() {
        Scan(scan => {
            scan.TheCallingAssembly();
        });

        var dictionary = new ModelBinderMappingDictionary();
        dictionary.Add<Car, CarModelBinder>();

        For<ModelBinderMappingDictionary>().Use(dictionary);
        For<IModelBinderProvider>().Singleton().Use<StructureMapModelBinderProvider>();
    }
}

使用Singleton一切正常！不确定Singleton范围是否适合这里？

使用结构图3注入自定义模型绑定器

2 个答案: