在StructureMap中使用策略的示例缺少依赖项

Question

我试图让例2了解如何在StructureMap中使用策略。我创建了一个小测试项目(下面的代码)。不幸的是，由于某些原因，似乎存在一些依赖问题，因为.As<type>和.Each都无法工作。

对于使用As的行，如

user.Green.As<Database>().ConnectionString.ShouldBe("*green*");

我发现了一个错误：

'IDatabase‘不包含'As’的定义，也不包含扩展方法，因为可以找到'IDatabase‘类型的第一个参数(您缺少使用指令或程序集引用吗？)对于这一行：

instance.Constructor.GetParameters()
                .Where(x => x.ParameterType == typeof(IDatabase))
                .Each(param => ...

“StringExtensions.Each(IEnumerable，Action)”由于其保护级别而无法访问。

我使用StructureMap 4.2安装了NuGet。正如您在下面的代码中所看到的，我将所有可以找到的using-statements从StructureMap中放进去，但我仍然有问题。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using StructureMap;
using StructureMap.Pipeline;
using StructureMap.Pipeline.Lazy;
using StructureMap.Configuration;
using StructureMap.Building;
using StructureMap.Attributes;
using StructureMap.AutoMocking;
using StructureMap.Graph;
using StructureMap.Query;
using StructureMap.TypeRules;
using StructureMap.Util;
using StructureMap.Building.Interception;
using StructureMap.Configuration.DSL;
using StructureMap.Diagnostics.TreeView;
using StructureMap.Graph.Scanning;

namespace TestStructureMapPolicies
{
    class Program
    {
        static void Main(string[] args)
        {
            var container = new Container(_ =>
            {
                _.For<IDatabase>().Add<Database>().Named("red")
                    .Ctor<string>("connectionString").Is("*red*");

                _.For<IDatabase>().Add<Database>().Named("green")
                    .Ctor<string>("connectionString").Is("*green*");

                _.Policies.Add<InjectDatabaseByName>();
            });


            // ImportantService should get the "red" database
            container.GetInstance<ImportantService>()
                .DB.As<Database>().ConnectionString.ShouldBe("*red*");

            // BigService should get the "green" database
            container.GetInstance<BigService>()
                .DB.As<Database>().ConnectionString.ShouldBe("*green*");

            // DoubleDatabaseUser gets both
            var user = container.GetInstance<DoubleDatabaseUser>();

            user.Green.As<Database>().ConnectionString.ShouldBe("*green*");
            user.Red.As<Database>().ConnectionString.ShouldBe("*red*");

        }
    }

    public interface IDatabase { }

    public class Database : IDatabase
    {
        public string ConnectionString { get; set; }

        public Database(string connectionString)
        {
            ConnectionString = connectionString;
        }

        public override string ToString()
        {
            return string.Format("ConnectionString: {0}", ConnectionString);
        }
    }

    public class InjectDatabaseByName : ConfiguredInstancePolicy
    {
        protected override void apply(Type pluginType, IConfiguredInstance instance)
        {
            instance.Constructor.GetParameters()
                .Where(x => x.ParameterType == typeof(IDatabase))
                .Each(param =>
                {
                        // Using ReferencedInstance here tells StructureMap
                        // to "use the IDatabase by this name"
                        var db = new ReferencedInstance(param.Name);
                    instance.Dependencies.AddForConstructorParameter(param, db);
                });
        }
    }

    public class BigService
    {
        public BigService(IDatabase green)
        {
            DB = green;
        }

        public IDatabase DB { get; set; }
    }

    public class ImportantService
    {
        public ImportantService(IDatabase red)
        {
            DB = red;
        }

        public IDatabase DB { get; set; }
    }

    public class DoubleDatabaseUser
    {
        public DoubleDatabaseUser(IDatabase red, IDatabase green)
        {
            Red = red;
            Green = green;
        }

        // Watch out for potential conflicts between setters
        // and ctor params. The easiest thing is to just make
        // setters private
        public IDatabase Green { get; private set; }
        public IDatabase Red { get; private set; }
    }
}

Answer 1

我在测试中使用的As<T>()扩展方法不是BCL的一部分，这就是您找不到它的原因。如果您正在使用Shouldly，您可以使用ShouldBeOfType<T>()来实现同样的效果，或者在进行比较之前将其转换为正常值。Each()扩展也是如此。