通过 Code First 方法使用 List<int> 属性创建数据库

Question

我正在尝试通过代码优先方法使用 MySQL 和我的实体创建一个数据库，但我在尝试时遇到了一些错误。该错误是：

InvalidOperationException: The property 'SymptomousInBodySublocations.HealthSymptomLocationIDs' could not be mapped, because it is of type 'List' which is not a supported primitive type or a valid entity type. Either explicitly map this property, or ignore it using the '[NotMapped]' attribute or by using 'EntityTypeBuilder.Ignore' in 'OnModelCreating'.

所以，我猜我可能会遇到这样的错误，但老实说我不知道如何处理它。

我的方法：

public static void InsertData()
{
    List<SymptomousInBodySublocations> SymtomsInBodySublocationsList = MedicService.SymptomsInBodySublocations();

    var semptominbodylocation = new SymptomousInBodySublocations();

    var context = new SymptomsRepo();

    using (context)
    {
        context.Database.EnsureCreated();
        foreach(SymptomousInBodySublocations symptomousInBodySublocations in SymtomsInBodySublocationsList)
        {
            semptominbodylocation.ID = symptomousInBodySublocations.ID;
            semptominbodylocation.Name = symptomousInBodySublocations.Name;
            semptominbodylocation.HasRedFlag = symptomousInBodySublocations.HasRedFlag;
            semptominbodylocation.HealthSymptomLocationIDs = symptomousInBodySublocations.HealthSymptomLocationIDs;
            semptominbodylocation.ProfName = symptomousInBodySublocations.ProfName;
            semptominbodylocation.Synonyms = symptomousInBodySublocations.Synonyms;
            context.SymptomousInBodySublocations.Add(semptominbodylocation);
            context.SaveChanges();
        }
    }
}

我的实体Class:

using System.Collections.Generic;

public class SymptomousInBodySublocations
{
    public int ID { get; set; }
    public string Name { get; set; }
    public bool HasRedFlag { get; set; }
    public List<int> HealthSymptomLocationIDs { get; set; }
    public string ProfName { get; set; }
    public List<string> Synonyms { get; set; }
}

我的背景Class:

using Microsoft.EntityFrameworkCore;

public class SymptomsRepo : DbContext
{
    public SymptomsRepo(){  }

    public SymptomsRepo(DbContextOptions<SymptomsRepo> options) :base(options){}
    public DbSet<SymptomousInBodySublocations> SymptomousInBodySublocations {get; set;}

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
      optionsBuilder.UseMySQL("server=localhost;database=Symptoms;user=root;password=password");
    }
    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
      base.OnModelCreating(modelBuilder);
    }
}

如何将其添加为列表或 table 中的单个功能？

Answer 1

哈林,

我很确定您的问题与此线程完全相同：

这是我通过复制您的错误消息并将其粘贴到 Google 中找到的。

您的问题正是错误消息所说的。将 C# class 映射到数据库 table 时，无法映射 List<>，因为 SQL 中没有 List<> 类型。意思是，没有 SQL 列可以具有 List<> 类型。 String、Int、DateTime……没问题。但是 SQL table 中的单个单元格并非旨在包含集合。它只能包含一个值。

您需要从 class 中删除此字段，或者用 [NotMapped] 修饰它，如下所示：

public class SymptomousInBodySublocations
{
    public int ID { get; set; }
    public string Name { get; set; }
    public bool HasRedFlag { get; set; }
    [NotMapped]
    public List<int> HealthSymptomLocationIDs { get; set; }
    public string ProfName { get; set; }
    [NotMapped]
    public List<string> Synonyms { get; set; }
}

通过 Code First 方法使用 List<int> 属性创建数据库

Creating A Database With List<int> Property Through Code First Approach

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通过 Code First 方法使用 List<int> 属性 创建数据库

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通过 Code First 方法使用 List<int> 属性创建数据库