在 StructureMap 中使用策略的示例缺少依赖项

Question

我正在尝试了解 example 2 如何在 StructureMap 中使用策略。我创建了一个小的测试项目（下面的代码）。不幸的是，由于某些原因似乎存在一些依赖性问题，因为 .As<type> 和 .Each 都不起作用。

对于使用As的行，例如

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

我收到错误：

'IDatabase' does not contain a definition for 'As' and no extension method 'As' accepting a first argument of type 'IDatabase' could be found (are you missing a using directive or assembly reference?). And for this line:

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

'StringExtensions.Each(IEnumberable,Action)' is inaccessible due to its protection level.

我使用 NuGet 安装了 StructureMap 4.2。正如您在下面的代码中看到的，我输入了我能找到的来自 StructureMap 的所有 using 语句，但我仍然遇到问题。

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。如果您使用的是 Shouldly，您可以使用 ShouldBeOfType<T>() 产生同样的效果，或者在进行比较之前正常投射它。 Each() 扩展也是如此。

在 StructureMap 中使用策略的示例缺少依赖项

Missing dependencies for an example of using policies in StructureMap

c#

structuremap