[英]Is it possible to exclude a constructor from autofac registration?
If I have the following class, is it possible to exclude the copy constructor from Autofac registration? 如果我有以下类,是否可以从Autofac注册中排除复制构造函数?
public class A
{
public A() {}
public A(A other) { // copy constructor }
public A(int b) { // some other stuff }
}
Basically, I would want autofac to resolve the default constructor, or if the user requested a Func<int, A>
the third constructor. 基本上,我希望autofac解析默认构造函数,或者如果用户请求Func<int, A>
第三个构造函数。 I never want autofac to resolve the copy constructor. 我从不希望autofac解析复制构造函数。 Is this possible? 这可能吗?
The reason for this is that when I try and use Autofac to inject a Func<A>
, it results in a circular dependency as Autofac is trying to use the second constructor (it thinks it knows a way to resolve A, but the way to resolve A requires an A). 原因是当我尝试使用Autofac注入Func<A>
,它会导致循环依赖,因为Autofac正在尝试使用第二个构造函数(它认为它知道解决A的方法,但是解决A需要A)。
You can implement your own constructor selector that ignores your second constructor: 您可以实现自己的构造函数选择器 ,忽略您的第二个构造函数:
public class AConstructorSelector : IConstructorSelector
{
public ConstructorParameterBinding SelectConstructorBinding(ConstructorParameterBinding[] constructorBindings)
{
if (constructorBindings == null) throw new ArgumentNullException("constructorBindings");
if (constructorBindings.Length == 0) throw new ArgumentOutOfRangeException("constructorBindings");
if (constructorBindings.Length == 1)
return constructorBindings[0];
var withLength = constructorBindings
.Where(b => !b.TargetConstructor.GetParameters().Select(p => p.ParameterType).Contains(typeof(A)))
.Select(binding => new { Binding = binding, ConstructorParameterLength = binding.TargetConstructor.GetParameters().Length })
.ToArray();
var maxLength = withLength.Max(binding => binding.ConstructorParameterLength);
var maximal = withLength
.Where(binding => binding.ConstructorParameterLength == maxLength)
.Select(ctor => ctor.Binding)
.ToArray();
if (maximal.Length == 1)
return maximal[0];
throw new DependencyResolutionException("Unable to find constructor");
}
}
And when register your class use it as parameter of the UsingConstructor
注册您的类时,请将其用作UsingConstructor
参数
var builder = new ContainerBuilder();
builder.RegisterType<A>().UsingConstructor(new AConstructorSelector());
Autofac 3.x will automatically create Implicit Relationship Types , eg Func<A>
, Lazy<B>
, etc. However you can override the default by registering your own. Autofac 3.x将自动创建隐式关系类型 ,例如Func<A>
, Lazy<B>
等。但是,您可以通过注册自己的默认值来覆盖默认值。
builder.Register<Func<int, A>>(c => (value) => { return new A(value); });
This is registering the Func<int, A>
signature and instructing which constructor to use to create this. 这是注册Func<int, A>
签名并指示使用哪个构造函数来创建它。
Try it out at .NET Fiddle, https://dotnetfiddle.net/CTFyo3 在.NET Fiddle上试一试, https: //dotnetfiddle.net/CTFyo3
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