具有默认参数的Unity构造函数

Question

使用默认参数注入构造函数的问题。

例如

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

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

错误：

[InvalidOperationException：类型Boolean没有可访问的构造函数。]
Microsoft.Practices.ObjectBuilder2.DynamicMethodConstructorStrategy.ThrowForNullExistingObject（IBuilderContext context）+239 lambda_method（Closure，IBuilderContext）+60
Microsoft.Practices.ObjectBuilder2。<> c__DisplayClass1.b__0（IBuilderContext context）+71
Microsoft.Practices.ObjectBuilder2.DynamicMethodBuildPlan.BuildUp（IBuilderContext context）+42
Microsoft.Practices.ObjectBuilder2.BuildPlanStrategy.PreBuildUp（IBuilderContext context）+333
Microsoft.Practices.ObjectBuilder2.StrategyChain.ExecuteBuildUp（IBuilderContext context）+274
Microsoft.Practices.ObjectBuilder2.BuilderContext.NewBuildUp（NamedTypeBuildKey newBuildKey）+167
Microsoft.Practices.Unity.ObjectBuilder.NamedTypeDependencyResolverPolicy.Resolve（IBuilderContext context）+101 lambda_method（Closure，IBuilderContext）+425
Microsoft.Practices.ObjectBuilder2。<> c__DisplayClass1.b__0（IBuilderContext context）+71
Microsoft.Practices.ObjectBuilder2.DynamicMethodBuildPlan.BuildUp（IBuilderContext context）+42
Microsoft.Practices.ObjectBuilder2.BuildPlanStrategy.PreBuildUp（IBuilderContext context）+333
Microsoft.Practices.ObjectBuilder2.StrategyChain.ExecuteBuildUp（IBuilderContext context）+274
Microsoft.Practices.ObjectBuilder2.BuilderContext.NewBuildUp（NamedTypeBuildKey newBuildKey）+167
Microsoft.Practices.Unity.ObjectBuilder.NamedTypeDependencyResolverPolicy.Resolve（IBuilderContext context）+101 lambda_method（Closure，IBuilderContext）+222
Microsoft.Practices.ObjectBuilder2。<> c__DisplayClass1.b__0（IBuilderContext context）+71
Microsoft.Practices.ObjectBuilder2.DynamicMethodBuildPlan.BuildUp（IBuilderContext context）+42
Microsoft.Practices.ObjectBuilder2.BuildPlanStrategy.PreBuildUp（IBuilderContext context）+333
Microsoft.Practices.ObjectBuilder2.StrategyChain.ExecuteBuildUp（IBuilderContext context）+274
Microsoft.Practices.Unity.UnityContainer.DoBuildUp（类型t，对象存在，字符串名称，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。

为了实现这一点，您有几个选择。 使用InjectionConstructor告诉注册表IAddressImportRepository ，并告诉它如何解析构造函数参数或将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));

要么

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

public bool IsUseSecurePredicate { get; set; }