C#反射Assembly IoC的一个实例

1.定义一个抽象类ServiceFactory，用来得到T接口的实现对象

public abstract class ServiceFactory
{
    public abstract T CreateService<T>() where T : class;
}

2.首先通过反射机制得到该interface的名字。得到该interface的实现实例后并缓存它。

/// <summary>
/// 直接引用提供服务
/// </summary>
public class RefServiceFactory : ServiceFactory
{
    public override T CreateService<T>()
    {
        //第一次通过反射创建服务实例，然后缓存住
        var interfaceName = typeof(T).Name;
        return CacheHelper.Get<T>(string.Format("Service_{0}", interfaceName), () =>
            {
                return AssemblyHelper.FindTypeByInterface<T>();
            });
    }
}

3.AssemblyHelper.FindTypeByInterface<T>();

该方法会在项目下的bin文件夹内查找dll文件，然后再去检测dll文件中的具体类

interfaceType.IsAssignableFrom(type) 判断type是否interfaceType的实现类
Activator.CreateInstance(type) 创建type类型的实例

/// <summary>
/// 扫描程序集找到实现了某个接口的第一个实例
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="searchpattern">文件名过滤</param>
/// <returns></returns>
public static T FindTypeByInterface<T>(string searchpattern = "*.dll") where T : class
{
    var interfaceType = typeof(T);

    string domain = GetBaseDirectory();
    string[] dllFiles = Directory.GetFiles(domain, searchpattern, SearchOption.TopDirectoryOnly);

    foreach (string dllFileName in dllFiles)
    {
        foreach (Type type in Assembly.LoadFrom(dllFileName).GetLoadableTypes())
        {
            if (interfaceType != type && interfaceType.IsAssignableFrom(type))
            {
                var instance = Activator.CreateInstance(type) as T;
                return instance;
            }
        }
    }

    return null;
}

/// <summary>
/// 得到当前应用程序的根目录
/// </summary>
/// <returns></returns>
public static string GetBaseDirectory()
{
    var baseDirectory = AppDomain.CurrentDomain.SetupInformation.PrivateBinPath;

    if (AppDomain.CurrentDomain.SetupInformation.PrivateBinPath == null)
        baseDirectory = AppDomain.CurrentDomain.BaseDirectory;

    return baseDirectory;
}