【Autofac笔记】解决循环依赖

定义类ClassA、ClassB

public class ClassA
{
    public ClassA(ClassB b)
    { }
}
public class ClassB
{
    public ClassB(ClassA a)
    { }
}

以下代码会抛出循环依赖异常

var containerBuilder = new ContainerBuilder();
containerBuilder.RegisterType<ClassA>();
containerBuilder.RegisterType<ClassB>();
var container = containerBuilder.Build();
using (var scope = container.BeginLifetimeScope())
{
    var a = scope.Resolve<ClassA>();
    var b = scope.Resolve<ClassB>();
}

解决方案

可以使用Lazy，避免抛出循环依赖异常
定义类ClassA、ClassB

public class ClassA
{
    public string Name => "A";
    private readonly Lazy<ClassB> _b = null;
    public ClassA(Lazy<ClassB> b)
    {
        _b = b;
    }
    public void Execute()
    {
        Console.WriteLine(_b.Value.Name);
    }
}
public class ClassB
{
    public string Name => "B";
    private readonly Lazy<ClassA> _a = null;
    public ClassB(Lazy<ClassA> a)
    {
        _a = a;
    }
    public void Execute()
    {
        Console.WriteLine(_a.Value.Name);
    }
}

var containerBuilder = new ContainerBuilder();
containerBuilder.RegisterType<ClassA>();
containerBuilder.RegisterType<ClassB>();
var container = containerBuilder.Build();
using (var scope = container.BeginLifetimeScope())
{
    var a = scope.Resolve<ClassA>();
    var b = scope.Resolve<ClassB>();
    a.Execute();//输出B
    b.Execute();//输出A
}

不会抛出异常