我正在尝试向表中添加一行,该表的外键指向同一表中的另一个位置。此外键定义为可为空。 尝试向表中添加条目时出现错误
"errors": {
"parentId": [
"Error converting value {null} to type 'System.Int32'. Path 'parentId', line 4, position 18."
]
},
如果我尝试传递一个随机 int,我会得到 The INSERT statement conflicted with the FOREIGN KEY constraint
,这是有道理的,因为表中没有其他条目。
如您所见,外键被视为可为空。
我尝试过完全不传递字段,传递字段时不传递任何参数,传递null,所有这些都产生了后来的错误,除了我尝试传递null时,它给了我转换错误。
我正在使用 swagger ui 来传递 JSON。
有问题的类:
public class
{
public Country Country { get; set; }
[Required]
public int CountryId { get; set; }
[Required]
public int Id { get; set; }
[Required]
public string Name { get; set; }
public int? ParentId { get; set; }
[ForeignKey("ParentId")]
public Company Parent { get; set; }
}
我想在此表上创建第一行并将其外键设置为空。
实现答案中建议的修复后,我的错误从转换错误变为上述外部约束错误,即使传递空值也是如此。
代码,根据要求:
数据库上下文:
public class ArtGalleriesContext:DbContext
{
public ArtGalleriesContext(DbContextOptions<ArtGalleriesContext> options):base(options)
{
}
public DbSet<ArtItem> ArtItems { get; set; }
public DbSet<Artist> Artists { get; set; }
public DbSet<Company> Companies { get; set; }
public DbSet<Country> Countries { get; set; }
public DbSet<Floor> Floors { get; set; }
public DbSet<Location> Locations { get; set; }
public DbSet<Room> Rooms { get; set; }
public DbSet<User> Users { get; set; }
public DbSet<UserLocation> UserLocations { get; set; }
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<UserLocation>()
.HasKey(u => new {u.UserId, u.LocationId});
}
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
if (!optionsBuilder.IsConfigured)
{
optionsBuilder.UseSqlServer(
"Server=(localdb)\\mssqllocaldb;Database=GalleriesDB;Trusted_Connection=True;");
}
}
}
Controller :
[HttpPost("Companies")]
public IActionResult CreateCompany([FromBody]CreateCompanyRequest createCompanyRequest)
{
try
{
if (createCompanyRequest==null)
{
return NotFound();
}
return CreatedAtRoute("CompanyById", _repository.Company.CreateCompany(createCompanyRequest),
createCompanyRequest);
}
catch (Exception e)
{
return StatusCode(500, e.InnerException);
}
}
存储库:
public int CreateCompany(CreateCompanyRequest createCompanyRequest)
{
Company company = new Company()
{
CountryId = createCompanyRequest.CountryId,
Name = createCompanyRequest.Name,
ParentId = createCompanyRequest.ParentId
};
_context.Companies.Add(company);
_context.SaveChanges();
return company.Id;
}
可能的相关信息:我尝试使用 Microsoft SQL Server Manager 填充表。它是成功的,然而,这是结果:
显然有问题,因为它从 PK 14 开始添加条目。
进一步检查后,我注意到即使向表中添加一行失败,主键仍然递增。
最佳答案
错误是在将json反序列化为模型时,您有两个选择:
添加到您的 startup.cs 类 Json 选项以忽略空值,如下所示:
.AddJsonOptions(options => { options.SerializerSettings.NullValueHandling = NullValueHandling.Ignore });
在属性本身上设置为忽略空值,以便它将
int?
初始化为 nullpublic class { public Country Country { get; set; } [Required] public int CountryId { get; set; } [Required] public int Id { get; set; } [Required] public string Name { get; set; } [JsonProperty(NullValueHandling = NullValueHandling.Ignore)] public int? ParentId { get; set; } [ForeignKey("ParentId")] public Company Parent { get; set; } }
关于c# - 尝试向表中添加行时无法将 Int32 转换为 null,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/58501992/