.NET：在ASPX、ASHX和MVC中使用IOC容器（菜鸟必看）

前言

程序开发的一个良好原则就是：“将使用和创建分开”。5年前有多少人采用这种风格呢？几乎没有。在IOC流行甚至泛滥的今天，还有一些团队没有使用IOC容器，有些是由于历史原因，有些是由于团队的文化。没有采用IOC的团队，找个机会拥抱一下吧。

我一直在用IOC容器，在此介绍一下如何将IOC集成到WebForm和WebMvc的应用系统中。

自动注入到ASPX和ASHX

框架支持

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Happy.Web
{
    public interface IWantAutoDependInjection
    {
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Happy.Web
{
    [AttributeUsage(AttributeTargets.Property, AllowMultiple = false)]
    public sealed class DependToAttribute : Attribute
    {
        public Type DependToType { get; set; }

        public string Key { get; set; }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

using System.Web;

using Microsoft.Practices.ServiceLocation;

using Happy.ExtensionMethods.Reflection;

namespace Happy.Web
{
    public class DependInjectionModule : IHttpModule
    {
        public void Init(HttpApplication context)
        {
            context.PreRequestHandlerExecute += OnPreRequestHandlerExecute;
        }

        private void OnPreRequestHandlerExecute(object sender, EventArgs e)
        {
            if (!(HttpContext.Current.CurrentHandler is IWantAutoDependInjection))
            {
                return;
            }

            var properties = HttpContext.Current.CurrentHandler.GetType().GetProperties();

            foreach (var property in properties)
            {
                var dependToAttribute = property.GetAttribute<DependToAttribute>(false);

                if (dependToAttribute == null)
                {
                    continue;
                }

                var dependType = dependToAttribute.DependToType ?? property.PropertyType;

                var value = ServiceLocator.Current.GetInstance(dependType, dependToAttribute.Key ?? string.Empty);

                property.SetValue(HttpContext.Current.Handler, value);
            }
        }

        public void Dispose()
        {
        }
    }
}

代码示例

<configuration>
  <system.web>
    <compilation debug="true" targetFramework="4.5" />
    <httpRuntime targetFramework="4.5" />
  </system.web>

  <system.webServer>
    <modules>
      <add name="DependInjectionModule" type="Happy.Web.DependInjectionModule"/>
    </modules>
  </system.webServer>

</configuration>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

using Happy.Web;

namespace WebStudy
{
    public partial class Test : System.Web.UI.Page, IWantAutoDependInjection
    {
        [DependTo]
        public ApplicationService ApplicationService { get; set; }

        protected void Page_Load(object sender, EventArgs e)
        {
            this.Response.Write(this.ApplicationService.GetMessage());
        }
    }

    public sealed class ApplicationService
    {
        public string GetMessage()
        {
            return "段光伟";
        }
    }
}

运行结果

 

自动注入到MVC

框架支持（最新版本）

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

using System.Web.Routing;
using System.Web.Mvc;

using Microsoft.Practices.ServiceLocation;

using Happy.DesignByContract;

namespace Happy.Web.Mvc
{
    public sealed class ServiceLocationDependencyResolver : IDependencyResolver
    {
        private readonly IServiceLocator _serviceLocator;

        public ServiceLocationDependencyResolver(IServiceLocator serviceLocator)
        {
            Check.RequireNotNull(serviceLocator, "serviceLocator");

            _serviceLocator = serviceLocator;
        }

        public object GetService(Type serviceType)
        {
            Check.RequireNotNull(serviceType, "serviceType");

            try
            {
                return _serviceLocator.GetInstance(serviceType);
            }
            catch
            {
                return null;
            }
        }

        public IEnumerable<object> GetServices(Type serviceType)
        {
            Check.RequireNotNull(serviceType, "serviceType");

            try
            {
                return _serviceLocator.GetAllInstances(serviceType);
            }
            catch
            {
                return new List<object>();
            }
        }
    }
}

代码示例

此处省略代码示例，有兴趣的朋友请留言交流。

备注

想象一下，开发人员只需要定义和声明，不需要手工组装（new）会有多爽。IOC容器的配置最好根据约定自动配置。