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.NET开发基础知识21-30

news 2025/7/10 1:59:54

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();

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