c# - 在 .NET Core 中使用字符串(配置文件)配置 ServiceCollection

Question

有没有一种方法可以在 .net core 的标准 Microsoft.Extensions.DependencyInjection.ServiceCollection 库中配置依赖注入(inject)，而不需要实际引用相关的实现类？ (从配置文件中获取实现类名？)

例如:

services.AddTransient<ISomething>("The.Actual.Thing");// Where The.Actual.Thing is a concrete class

Answer 1

如果您真的热衷于使用字符串参数动态加载对象，您可以使用创建动态对象的工厂。

public interface IDynamicTypeFactory
{
    object New(string t);
}
public class DynamicTypeFactory : IDynamicTypeFactory
{
    object IDynamicTypeFactory.New(string t)
    {
        var asm = Assembly.GetEntryAssembly();
        var type = asm.GetType(t);
        return Activator.CreateInstance(type);
    }
}

假设您有以下服务

public interface IClass
{
    string Test();
}
public class Class1 : IClass
{
    public string Test()
    {
        return "TEST";
    }
}

然后你就可以

public void ConfigureServices(IServiceCollection services)
    {   
        services.AddTransient<IDynamicTypeFactory, DynamicTypeFactory>();
    }

    // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
    public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory, IDynamicTypeFactory dynamicTypeFactory)
    {
        loggerFactory.AddConsole();

        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }

        app.Run(async (context) =>
        {
            var t = (IClass)dynamicTypeFactory.New("WebApplication1.Class1");
            await context.Response.WriteAsync(t.Test());
        });
    }