Question

使用默认参数注入构造函数时出现问题。

例如

container.RegisterType<IAddressImportRepository, AddressImportRepository>(
    new PerRequestLifetimeManager());

public AddressImportRepository(
    FairFlexxDbContext context, bool isUseSecurePredicate = true)
    : base(context, isUseSecurePredicate)
{
}

错误：

[InvalidOperationException：布尔类型没有   可访问的构造函数。]
  Microsoft.Practices.ObjectBuilder2.DynamicMethodConstructorStrategy.ThrowForNullExistingObject（IBuilderContext   上下文）+239 lambda_method（Closure，IBuilderContext）+60
  Microsoft.Practices.ObjectBuilder2＆LT;＆GT; c__DisplayClass1.b__0（IBuilderContext   上下文）+71
  Microsoft.Practices.ObjectBuilder2.DynamicMethodBuildPlan.BuildUp（IBuilderContext   上下文）+42
  Microsoft.Practices.ObjectBuilder2.BuildPlanStrategy.PreBuildUp（IBuilderContext   上下文）+333
  Microsoft.Practices.ObjectBuilder2.StrategyChain.ExecuteBuildUp（IBuilderContext   上下文）+274
  Microsoft.Practices.ObjectBuilder2.BuilderContext.NewBuildUp（NamedTypeBuildKey   newBuildKey）+167
  Microsoft.Practices.Unity.ObjectBuilder.NamedTypeDependencyResolverPolicy.Resolve（IBuilderContext   上下文）+101 lambda_method（Closure，IBuilderContext）+425
  Microsoft.Practices.ObjectBuilder2＆LT;＆GT; c__DisplayClass1.b__0（IBuilderContext   上下文）+71
  Microsoft.Practices.ObjectBuilder2.DynamicMethodBuildPlan.BuildUp（IBuilderContext   上下文）+42
  Microsoft.Practices.ObjectBuilder2.BuildPlanStrategy.PreBuildUp（IBuilderContext   上下文）+333
  Microsoft.Practices.ObjectBuilder2.StrategyChain.ExecuteBuildUp（IBuilderContext   上下文）+274
  Microsoft.Practices.ObjectBuilder2.BuilderContext.NewBuildUp（NamedTypeBuildKey   newBuildKey）+167
  Microsoft.Practices.Unity.ObjectBuilder.NamedTypeDependencyResolverPolicy.Resolve（IBuilderContext   上下文）+101 lambda_method（Closure，IBuilderContext）+222
  Microsoft.Practices.ObjectBuilder2＆LT;＆GT; c__DisplayClass1.b__0（IBuilderContext   上下文）+71
  Microsoft.Practices.ObjectBuilder2.DynamicMethodBuildPlan.BuildUp（IBuilderContext   上下文）+42
  Microsoft.Practices.ObjectBuilder2.BuildPlanStrategy.PreBuildUp（IBuilderContext   上下文）+333
  Microsoft.Practices.ObjectBuilder2.StrategyChain.ExecuteBuildUp（IBuilderContext   上下文）+274
  Microsoft.Practices.Unity.UnityContainer.DoBuildUp（Type t，Object   existing，String name，IEnumerable`1 resolverOverrides）+383

Answer 1

Unity使用反射来确定构造函数参数类型。使用构造函数，它找到了参数FairFlexxDbContext和bool。它试图构造每种类型的实例并在bool上失败，因为它是一个值类型。它无法识别您提供的默认值以通过此错误。

要实现这一点，您有几个选择。要么使用InjectionConstructor告诉注册表IAddressImportRepository并告诉如何解析构造函数参数，要么将bool参数移动为属性。由于bool是一个可选参数，我建议将其移动为属性。

container.RegisterType<IAddressImportRepository, AddressImportRepository>(
    new PerRequestLifetimeManager(), 
    new InjectionConstructor(new ResolvedParameter<FairFlexxDbContext>(), true));

或

public AddressImportRepository(FairFlexxDbContext context)
    : base(context, true)
{
    IsUseSecurePredicate = true;
}

public bool IsUseSecurePredicate { get; set; }

具有默认参数的Unity构造函数

1 个答案: