在ASP.NET中實現MySQL的讀寫分離，可以通過以下幾個步驟來完成：

1. 安裝必要的庫

首先，你需要安裝一些必要的庫來連接MySQL數據庫。你可以使用MySql.Data.EntityFrameworkCore來簡化數據庫操作。

dotnet add package MySql.Data.EntityFrameworkCore
dotnet add package Pomelo.EntityFrameworkCore.MySql

2. 配置數據庫連接

在你的appsettings.json文件中配置多個數據庫連接字符串，分別用于讀和寫操作。

{
  "ConnectionStrings": {
    "DefaultConnection": "server=read_host;port=3306;database=mydatabase;user=myuser;password=mypassword",
    "WriteConnection": "server=write_host;port=3306;database=mydatabase;user=myuser;password=mypassword"
  }
}

3. 創建DbContext

創建一個繼承自DbContext的類，并配置連接字符串。

using Microsoft.EntityFrameworkCore;

public class MyDbContext : DbContext
{
    public MyDbContext(DbContextOptions<MyDbContext> options) : base(options) { }

    public DbSet<MyEntity> MyEntities { get; set; }
}

4. 配置讀寫分離策略

你可以使用DbContextOptionsBuilder來配置讀寫分離策略。以下是一個示例：

using Microsoft.EntityFrameworkCore;
using MySql.Data.EntityFrameworkCore;

public class MyDbContext : DbContext
{
    public MyDbContext(DbContextOptions<MyDbContext> options) : base(options) { }

    public DbSet<MyEntity> MyEntities { get; set; }
}

public class ReadWriteDbContextFactory
{
    private readonly string _writeConnectionString;
    private readonly string _readConnectionString;

    public ReadWriteDbContextFactory(string writeConnectionString, string readConnectionString)
    {
        _writeConnectionString = writeConnectionString;
        _readConnectionString = readConnectionString;
    }

    public MyDbContext CreateWriteContext()
    {
        var optionsBuilder = new DbContextOptionsBuilder<MyDbContext>();
        optionsBuilder.UseMySQL(_writeConnectionString);
        return new MyDbContext(optionsBuilder.Options);
    }

    public MyDbContext CreateReadContext()
    {
        var optionsBuilder = new DbContextOptionsBuilder<MyDbContext>();
        optionsBuilder.UseMySQL(_readConnectionString);
        return new MyDbContext(optionsBuilder.Options);
    }
}

5. 使用讀寫分離策略

在你的服務或控制器中，使用ReadWriteDbContextFactory來獲取讀寫分離的MyDbContext實例。

public class MyService
{
    private readonly ReadWriteDbContextFactory _dbContextFactory;

    public MyService(ReadWriteDbContextFactory dbContextFactory)
    {
        _dbContextFactory = dbContextFactory;
    }

    public async Task SaveAsync(MyEntity entity)
    {
        using (var context = _dbContextFactory.CreateWriteContext())
        {
            context.MyEntities.Add(entity);
            await context.SaveChangesAsync();
        }
    }

    public async Task<MyEntity> GetAsync(int id)
    {
        using (var context = _dbContextFactory.CreateReadContext())
        {
            return await context.MyEntities.FindAsync(id);
        }
    }
}

6. 配置依賴注入

在你的Startup.cs或Program.cs中配置依賴注入。

public void ConfigureServices(IServiceCollection services)
{
    services.AddDbContext<MyDbContext>(options =>
        options.UseMySQL(Configuration.GetConnectionString("DefaultConnection")));

    services.AddScoped<ReadWriteDbContextFactory>(sp =>
        new ReadWriteDbContextFactory(
            Configuration.GetConnectionString("WriteConnection"),
            Configuration.GetConnectionString("ReadConnection")));

    services.AddScoped<MyService>();
}

通過以上步驟，你就可以在ASP.NET中實現MySQL的讀寫分離了。讀操作會連接到讀數據庫，而寫操作會連接到寫數據庫，從而提高系統的性能和可靠性。