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[英]Xamarin Forms Dependency Injection with Microsoft.Extensions.DependencyInjection
[英]Dependency injection using Services with Microsoft.Extensions.DependencyInjection library
为什么在第二次 scope 创建后未调用 ScopedOperation 构造函数?
资料来源: https://dotnetfiddle.net/wtyP9n
using System;
using Microsoft.Extensions.DependencyInjection;
public class Program
{
public static void Main()
{
添加服务:
var serviceProvider = new ServiceCollection()
.AddTransient<TransientOperation>() //Create a Simple Transient Service that writes a text on creation
.AddScoped<ScopedOperation>() //Create a Simple Scoped Service that writes a text on creation
.AddSingleton<SingletonOperation>() //Create a Simple Singleton Service that writes a text on creation
构建服务并发出第一个请求:
serviceProvider.BuildServiceProvider();
Console.WriteLine("Initiating Service Operations");
Console.WriteLine("\n-------- First Request --------");
//With the scope the aim is to see if after the using(), which service will be destroyed
using (var scope = serviceProvider.CreateScope())
{
var singletonService = serviceProvider.GetService<SingletonOperation>();
var scopedService = serviceProvider.GetService<ScopedOperation>();
var transientService = serviceProvider.GetService<TransientOperation>();
} //Why the disposed methods of Scoped and Transient Services are not being called ?
继续第二个请求:
Console.WriteLine("\n-------- Second Request --------");
using (var scope = serviceProvider.CreateScope()) //adding the same singleton, scope and transient services agains
{
var singletonService = serviceProvider.GetService<SingletonOperation>();
var scopedService = serviceProvider.GetService<ScopedOperation>();
var transientService = serviceProvider.GetService<TransientOperation>();
} //Why the disposed methods of Scoped and Transient Services are not being called ?
Console.WriteLine();
Console.WriteLine(new String('-',30));
Console.WriteLine("Operations Concluded!");
Console.ReadLine();
}
}
//DEFINING THE SERVICES
服务:
public class SingletonOperation:IDisposable
{ private bool _disposed = false;
public SingletonOperation() => Console.WriteLine("Singleton Service created!");
public void Dispose() { if (_disposed) return; Console.WriteLine("SingletonService Disposed!"); _disposed = true;}
~SingletonOperation() => Dispose();
}
public class ScopedOperation:IDisposable
{
private bool _disposed = false;
public ScopedOperation() => Console.WriteLine("Scoped Service created!");
public void Dispose() { if (_disposed) return; Console.WriteLine("ScopedService Disposed!");_disposed = true; }
~ScopedOperation()=>Dispose();
}
public class TransientOperation:IDisposable
{ private bool _disposed = false;
public TransientOperation() => Console.WriteLine("Transient Service created!");
public void Dispose(){ if (_disposed) return; Console.WriteLine("TransientService Disposed!"); _disposed = true; }
~TransientOperation() => Dispose();
}
显示完整结果:
请注意,在第二个请求中,调用了 Transient Service 构造函数,但我希望也调用 ScopedService 构造函数,因为它位于不同的 scope 中。 为什么它没有被调用?
//为什么没有调用Scoped和Transient Services的disposed方法?
您的示例的提供者没有被处置,因此它创建的服务也不会被处置。 您示例中的所有GetService
调用都属于同一个 scope。
使用创建的 scope 的提供者来获得所需的行为
//...
using (IServiceScope scope = serviceProvider.CreateScope()) {
var singletonService = scope.ServiceProvider.GetService<SingletonOperation>();
var scopedService = scope.ServiceProvider.GetService<ScopedOperation>();
var transientService = scope.ServiceProvider.GetService<TransientOperation>();
}
//...
对提供的小提琴进行上述更改会产生以下 output
Initiating Service Operations
-------- First Request --------
Singleton Service created!
Scoped Service created!
Transient Service created!
TransientService Disposed!
ScopedService Disposed!
Executing DemoService Operation number: 0
Executing DemoService Operation number: 1
Initialized valued on service was: 10
Adding object of type Client
I am Service A
I am Service B
I am Service B
-------- Second Request --------
Scoped Service created!
Transient Service created!
TransientService Disposed!
ScopedService Disposed!
------------------------------
Operations Concluded!
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