Autofac PropertiesAutowired - 是否可以忽略一个或多个属性？

尽管建议通过构造函数传递依赖项，但我发现使用无参数构造函数然后自动装配所有属性的开发成本显着减少，并使应用程序更易于开发和维护。然而有时（例如在视图模型上）我有一个在容器中注册的属性，但我不想在构造时填充该属性（例如绑定到容器的所选项目）。

有没有办法告诉容器在自动装配其余属性时忽略某些属性？

目前，我只是重置在激活事件中标有属性的属性：

public static IRegistrationBuilder<TLimit, ScanningActivatorData, TRegistrationStyle> 
    PropertiesAutowiredExtended<TLimit, TRegistrationStyle>(
    this IRegistrationBuilder<TLimit, ScanningActivatorData, TRegistrationStyle> builder)
{
    builder.ActivatorData.ConfigurationActions.Add(
        (type, innerBuilder) =>
        {
            var parameter = Expression.Parameter(typeof(object));
            var cast = Expression.Convert(parameter, type);
            var assignments = type.GetProperties()
                .Where(candidate => candidate.HasAttribute<NotAutowiredAttribute>())
                .Select(property => new { Property = property, Expression = Expression.Property(cast, property) })
                .Select(data => Expression.Assign(data.Expression, Expression.Default(data.Property.PropertyType)))
                .Cast<Expression>()
                .ToArray();

            if (assignments.Any())
            {
                var @action = Expression
                    .Lambda<Action<object>>(Expression.Block(assignments), parameter)
                    .Compile();

                innerBuilder.OnActivated(e =>
                {
                    e.Context.InjectUnsetProperties(e.Instance);
                    @action(e.Instance);
                });
            }
            else
            {
                innerBuilder.OnActivated(e => e.Context.InjectUnsetProperties(e.Instance));
            }
        });

    return builder;
}

有一个更好的方法吗？

不确定这是一个更好的方法，但您可以从另一侧出发，通过 WithProperty 语法仅注册所需的属性。优点是 Autofac 不会解决不必要的服务。这是一个工作示例：

public class MyClass
{
    public MyDependency MyDependency { get; set; }
    public MyDependency MyExcludeDependency { get; set; }
}
public class MyDependency {}

public class Program
{
    public static void Main(string[] args)
    {
        var builder = new ContainerBuilder();
        builder.RegisterType<MyDependency>();
        builder.RegisterType<MyClass>().WithPropertiesAutowiredExcept("MyExcludeDependency");

        using (var container = builder.Build())
        {
            var myClass = container.Resolve<MyClass>();

            Console.WriteLine(myClass.MyDependency == null);
            Console.WriteLine(myClass.MyExcludeDependency == null);
        }
    }
}

public static class PropertiesAutowiredExtensions
{
    // Extension that registers only needed properties
    // Filters by property name for simplicity
    public static IRegistrationBuilder<TLimit, TReflectionActivatorData, TRegistrationStyle>
        WithPropertiesAutowiredExcept<TLimit, TReflectionActivatorData, TRegistrationStyle>(
        this IRegistrationBuilder<TLimit, TReflectionActivatorData, TRegistrationStyle> registrationBuilder,
        params string[] propertiesNames)
        where TReflectionActivatorData : ReflectionActivatorData
    {
        var type = ((IServiceWithType)registrationBuilder.RegistrationData.Services.Single()).ServiceType;

        foreach (var property in type
            .GetProperties(BindingFlags.Public | BindingFlags.Instance)
            .Where(pi => pi.CanWrite && !propertiesNames.Contains(pi.Name)))
        {
            // There's no additional checks like in PropertiesAutowired for simplicity
            // You can add them from Autofac.Core.Activators.Reflection.AutowiringPropertyInjector.InjectProperties

            var localProperty = property;
            registrationBuilder.WithProperty(
                new ResolvedParameter(
                    (pi, c) =>
                        {
                            PropertyInfo prop;
                            return pi.TryGetDeclaringProperty(out prop) &&
                                   prop.Name == localProperty.Name;
                        },
                    (pi, c) => c.Resolve(localProperty.PropertyType)));
        }

        return registrationBuilder;
    }

    // From Autofac.Util.ReflectionExtensions
    public static bool TryGetDeclaringProperty(this ParameterInfo pi, out PropertyInfo prop)
    {
        var mi = pi.Member as MethodInfo;
        if (mi != null && mi.IsSpecialName && mi.Name.StartsWith("set_", StringComparison.Ordinal)
            && mi.DeclaringType != null)
        {
            prop = mi.DeclaringType.GetProperty(mi.Name.Substring(4));
            return true;
        }

        prop = null;
        return false;
    }
}