.NET Minimal API无法连接MySQL实例的问题求助

问题场景 #

搭建了.NET Minimal API项目，已配置MarketDb上下文连接Docker中的MySQL实例，/hello端点可正常返回结果，但访问/regions端点时抛出以下错误：

System.InvalidOperationException: No database provider has been configured for this DbContext. A provider can be configured by overriding the 'DbContext.OnConfiguring' method or by using 'AddDbContext' on the application service provider. If 'AddDbContext' is used, then also ensure that your DbContext type accepts a DbContextOptions object in its constructor and passes it to the base constructor for DbContext.

数据库可通过adminer容器和MySQL浏览器正常访问，上下文配置看起来符合要求，但问题依旧。

核心错误原因 #

所有实体模型类（TypeId、RegionId、MarketData、CompletedDates）都错误地继承了DbContext。DbContext是EF Core中负责数据库交互的上下文类，实体模型应该是普通的POCO（Plain Old CLR Object）类，不需要继承DbContext。当EF Core尝试加载这些实体时，会将它们当作未配置的DbContext实例处理，从而触发上述错误。

修复方案 #

移除所有实体类的: DbContext继承，仅保留MarketDb作为项目中唯一的DbContext类。

修正后的实体类代码示例 #

TypeId.cs

using System.ComponentModel.DataAnnotations.Schema;
using System.Collections.Generic;

namespace Api.Models
{
  [Table("type_id")]
  public class TypeId
  {
    public int Id { get; set; }
    public string Value { get; set; }
    public ICollection<MarketData> MarketData { get; set; } = new List<MarketData>();

    public TypeId(int id, string value)
    {
      Id = id;
      Value = value ?? throw new ArgumentNullException(nameof(value));
    }
  }
}

RegionId.cs

using System.ComponentModel.DataAnnotations.Schema;
using System.Collections.Generic;

namespace Api.Models
{
  [Table("region_id")]
  public class RegionId
  {
    public int Id { get; set; }
    public string Value { get; set; }
    public ICollection<MarketData> MarketData { get; set; } = new List<MarketData>();

    public RegionId(int id, string value)
    {
      Id = id;
      Value = value ?? throw new ArgumentNullException(nameof(value));
    }
  }
}

MarketData.cs

using System.ComponentModel.DataAnnotations.Schema;
using System.Collections.Generic;

namespace Api.Models
{
  [Table("market_data")]
  [PrimaryKey(nameof(DateID), nameof(RegionID), nameof(TypeID))]
  public class MarketData
  {
    public int DateID { get; set; }
    public CompletedDates Date { get; set; }

    public int RegionID { get; set; }
    public RegionId Region { get; set; }
    public int TypeID { get; set; }
    public TypeId Type { get; set; }
    public double Average { get; set; }
    public double Highest { get; set; }
    public double Lowest { get; set; }
    public long Volume { get; set; }
    public long OrderCount { get; set; }

    public MarketData(int dateID, CompletedDates completedDate, int regionID, RegionId region, int typeID, TypeId type, double average, double highest, double lowest, long volume, long orderCount)
    {
      DateID = dateID;
      Date = completedDate ?? throw new ArgumentNullException(nameof(completedDate));
      RegionID = regionID;
      Region = region ?? throw new ArgumentNullException(nameof(region));
      TypeID = typeID;
      Type = type ?? throw new ArgumentNullException(nameof(type));
      Average = average;
      Highest = highest;
      Lowest = lowest;
      Volume = volume;
      OrderCount = orderCount;
    }
  }
}

CompletedDates.cs

using System.ComponentModel.DataAnnotations.Schema;
using System.Collections.Generic;

namespace Api.Models
{
  [Table("completed_dates")]
  public class CompletedDates
  {
    public int Id { get; set; }
    public DateOnly Date { get; set; }
    public ICollection<MarketData> MarketData { get; set; } = new List<MarketData>();
  }
}

额外优化建议 #

为实体类添加无参数构造函数（可设为私有，EF Core可通过反射访问），避免EF Core实例化实体时出现异常：

// 在RegionId类中添加
private RegionId() { }

内容的提问来源于stack exchange，提问作者Catradora