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21. 自定义配置源

• 技术知识：除了默认的配置源（如 appsettings.json），你可以自定义配置源，从不同的数据源（如数据库、网络服务等）加载配置信息，以满足多样化的配置需求。

• 案例：

CustomConfigSource.cs

using Microsoft.Extensions.Configuration;
using System;public class CustomConfigSource : IConfigurationSource
{public IConfigurationProvider Build(IConfigurationBuilder builder){return new CustomConfigProvider();}
}public class CustomConfigProvider : ConfigurationProvider
{public override void Load(){// 模拟从自定义数据源加载配置Data["CustomSetting"] = "CustomValue";}
}

Program.cs

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;var builder = WebApplication.CreateBuilder(args);// 添加自定义配置源
builder.Configuration.Add(new CustomConfigSource());var app = builder.Build();var config = app.Services.GetRequiredService<IConfiguration>();
var customSetting = config["CustomSetting"];
Console.WriteLine($"Custom Setting Value: {customSetting}");app.Run();

22. 配置绑定到对象集合

• 技术知识：可以将配置文件中的数组或列表数据绑定到对象集合，方便处理批量配置信息。

• 案例：

Program.cs

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using System.Collections.Generic;public class MyItem
{public string Name { get; set; }public int Value { get; set; }
}var builder = WebApplication.CreateBuilder(args);var myItems = new List<MyItem>();
builder.Configuration.Bind("MyItems", myItems);var app = builder.Build();foreach (var item in myItems)
{Console.WriteLine($"Name: {item.Name}, Value: {item.Value}");
}app.Run();

appsettings.json

{"MyItems": [{"Name": "Item1","Value": 10},{"Name": "Item2","Value": 20}]
}    

23. 中间件委托

• 技术知识：中间件可以使用委托来定义，这种方式更加灵活，可以在不创建类的情况下实现中间件逻辑。

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Hosting;
using System.Threading.Tasks;var builder = WebApplication.CreateBuilder(args);
var app = builder.Build();// 使用中间件委托
app.Use(async (context, next) =>
{Console.WriteLine("Before processing request in delegate middleware");await next();Console.WriteLine("After processing request in delegate middleware");
});app.Run(async context =>
{await context.Response.WriteAsync("Hello from application");
});app.Run();

24. 控制器模型绑定自定义

• 技术知识：可以自定义控制器的模型绑定规则，处理特殊的数据格式或复杂的对象绑定。

• 案例：

CustomModelBinder.cs

using Microsoft.AspNetCore.Mvc.ModelBinding;
using System.Threading.Tasks;public class CustomModelBinder : IModelBinder
{public Task BindModelAsync(ModelBindingContext bindingContext){var valueProviderResult = bindingContext.ValueProvider.GetValue(bindingContext.ModelName);if (valueProviderResult != ValueProviderResult.None){var value = valueProviderResult.FirstValue;if (!string.IsNullOrEmpty(value)){// 自定义绑定逻辑bindingContext.Result = ModelBindingResult.Success($"Custom: {value}");}}return Task.CompletedTask;}
}

MyController.cs

using Microsoft.AspNetCore.Mvc;[ApiController]
[Route("[controller]")]
public class MyController : ControllerBase
{[HttpGet]public IActionResult Get([ModelBinder(typeof(CustomModelBinder))] string input){return Ok(input);}
}

Program.cs

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;var builder = WebApplication.CreateBuilder(args);
builder.Services.AddControllers();var app = builder.Build();app.UseRouting();
app.MapControllers();app.Run();

25. 基于策略的授权

• 技术知识：基于策略的授权允许你定义复杂的授权规则，将多个授权条件组合成一个策略，方便管理和复用。

MyController.cs

using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Mvc;[ApiController]
[Route("[controller]")]
public class MyController : ControllerBase
{[HttpGet][Authorize(Policy = "AdminPolicy")]public IActionResult Get(){return Ok("Authorized as Admin");}
}

Program.cs 

using Microsoft.AspNetCore.Authentication.JwtBearer;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.IdentityModel.Tokens;
using System.Text;var builder = WebApplication.CreateBuilder(args);// 配置 JWT 认证
builder.Services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme).AddJwtBearer(options =>{options.TokenValidationParameters = new TokenValidationParameters{ValidateIssuer = true,ValidateAudience = true,ValidateLifetime = true,ValidateIssuerSigningKey = true,ValidIssuer = "YourIssuer",ValidAudience = "YourAudience",IssuerSigningKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes("YourSecretKey"))};});// 定义授权策略
builder.Services.AddAuthorization(options =>
{options.AddPolicy("AdminPolicy", policy =>policy.RequireRole("Admin"));
});builder.Services.AddControllers();var app = builder.Build();app.UseAuthentication();
app.UseAuthorization();app.MapControllers();app.Run();

26. 应用程序配置重载

• 技术知识：在应用程序运行过程中，可以手动触发配置的重载，以加载最新的配置信息，而无需重启应用。

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using System;
using System.Threading;var builder = WebApplication.CreateBuilder(args);var config = builder.Configuration;
var mySetting = config["MySetting"];
Console.WriteLine($"Initial MySetting value: {mySetting}");var reloadToken = config.GetReloadToken();
var cancellationTokenSource = new CancellationTokenSource();// 模拟定时重载配置
new Thread(() =>
{while (!cancellationTokenSource.Token.IsCancellationRequested){Thread.Sleep(5000);reloadToken = config.Reload();mySetting = config["MySetting"];Console.WriteLine($"Reloaded MySetting value: {mySetting}");}
}).Start();var app = builder.Build();app.Run();

27. 路由约束

• 技术知识：路由约束可以对路由参数进行验证，确保只有符合特定条件的参数才能匹配路由，提高路由的准确性。

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Routing;
using Microsoft.Extensions.Hosting;var builder = WebApplication.CreateBuilder(args);
var app = builder.Build();app.UseRouting();app.UseEndpoints(endpoints =>
{endpoints.MapGet("/products/{id:int}", async context =>{var id = Convert.ToInt32(context.Request.RouteValues["id"]);await context.Response.WriteAsync($"Product ID: {id}");});
});app.Run();

28. 依赖注入服务替换

• 技术知识：在某些情况下，你可能需要替换已注册的服务实现，以满足不同的需求或进行测试。

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;// 定义服务接口
public interface IMyService
{void DoSomething();
}// 定义默认服务实现
public class MyDefaultService : IMyService
{public void DoSomething(){Console.WriteLine("Default service is doing something");}
}// 定义替换服务实现
public class MyReplacementService : IMyService
{public void DoSomething(){Console.WriteLine("Replacement service is doing something");}
}var builder = WebApplication.CreateBuilder(args);// 注册默认服务
builder.Services.AddTransient<IMyService, MyDefaultService>();// 替换服务实现
builder.Services.AddTransient<IMyService, MyReplacementService>();var app = builder.Build();var service = app.Services.GetRequiredService<IMyService>();
service.DoSomething();app.Run();

10. 配置变更通知

• 技术知识：当配置发生变更时，可以通过监听配置变更通知来执行相应的操作，如重新加载缓存、更新服务状态等。

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;var builder = WebApplication.CreateBuilder(args);var config = builder.Configuration;
var mySetting = config["MySetting"];
Console.WriteLine($"Initial MySetting value: {mySetting}");var changeToken = config.GetReloadToken();
changeToken.RegisterChangeCallback(state =>
{var newConfig = (IConfiguration)state;var newMySetting = newConfig["MySetting"];Console.WriteLine($"MySetting value has changed to: {newMySetting}");// 重新获取变更通知令牌changeToken = newConfig.GetReloadToken();changeToken.RegisterChangeCallback(state, newConfig);
}, config);var app = builder.Build();app.Run();