我们有3个模型类：
主持人有很多比赛分母。 TournamentBatch具有许多TournamentBatchItem。在TournamentBatch表中将有FK主机。
我们确实对ApplicationDbContext中的SaveChangesAsync进行了覆盖，以允许如下所示的软删除：
public override Task<int> SaveChangesAsync(bool acceptAllChangesOnSuccess, CancellationToken cancellationToken = default(CancellationToken))
{
OnBeforeSaving();
return base.SaveChangesAsync(acceptAllChangesOnSuccess, cancellationToken);
}
private void OnBeforeSaving()
{
if (_httpContextAccessor.HttpContext != null)
{
var userName = _httpContextAccessor.HttpContext.User.Identity.Name;
var userId = _httpContextAccessor.HttpContext.User.FindFirstValue(ClaimTypes.NameIdentifier);
// Added
var added = ChangeTracker.Entries().Where(v => v.State == EntityState.Added && typeof(IBaseEntity).IsAssignableFrom(v.Entity.GetType())).ToList();
added.ForEach(entry =>
{
((IBaseEntity)entry.Entity).DateCreated = DateTime.UtcNow;
((IBaseEntity)entry.Entity).CreatedBy = userId;
((IBaseEntity)entry.Entity).LastDateModified = DateTime.UtcNow;
((IBaseEntity)entry.Entity).LastModifiedBy = userId;
});
// Modified
var modified = ChangeTracker.Entries().Where(v => v.State == EntityState.Modified &&
typeof(IBaseEntity).IsAssignableFrom(v.Entity.GetType())).ToList();
modified.ForEach(entry =>
{
((IBaseEntity)entry.Entity).LastDateModified = DateTime.UtcNow;
((IBaseEntity)entry.Entity).LastModifiedBy = userId;
});
// Deleted
var deleted = ChangeTracker.Entries().Where(v => v.State == EntityState.Deleted &&
typeof(IBaseEntity).IsAssignableFrom(v.Entity.GetType())).ToList();
// var deleted = ChangeTracker.Entries().Where(v => v.State == EntityState.Deleted).ToList();
deleted.ForEach(entry =>
{
((IBaseEntity)entry.Entity).DateDeleted = DateTime.UtcNow;
((IBaseEntity)entry.Entity).DeletedBy = userId;
});
foreach (var entry in ChangeTracker.Entries()
.Where(e => e.State == EntityState.Deleted &&
e.Metadata.GetProperties().Any(x => x.Name == "IsDeleted")))
{
switch (entry.State)
{
case EntityState.Added:
entry.CurrentValues["IsDeleted"] = false;
break;
case EntityState.Deleted:
entry.State = EntityState.Modified;
entry.CurrentValues["IsDeleted"] = true;
break;
}
}
}
else
{
// DbInitializer kicks in
}
}
在我们的模型中：
using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using System.Linq;
using System.Threading.Tasks;
namespace AthlosifyWebArchery.Models
{
public class TournamentBatch : IBaseEntity
{
[Key]
public Guid TournamentBatchID { get; set; }
public Guid HostID { get; set; }
public string Name { get; set; }
public string BatchFilePath { get; set; }
[Display(Name = "Batch File Size (bytes)")]
[DisplayFormat(DataFormatString = "{0:N1}")]
public long BatchFileSize { get; set; }
[Display(Name = "Uploaded (UTC)")]
[DisplayFormat(DataFormatString = "{0:F}")]
public DateTime DateUploaded { get; set; }
public DateTime DateCreated { get; set; }
public string CreatedBy { get; set; }
public DateTime LastDateModified { get; set; }
public string LastModifiedBy { get; set; }
public DateTime? DateDeleted { get; set; }
public string DeletedBy { get; set; }
public bool IsDeleted { get; set; }
public Host Host { get; set; }
public ICollection<TournamentBatchItem> TournamentBatchItems { get; set; }
[Timestamp]
public byte[] RowVersion { get; set; }
[ForeignKey("CreatedBy")]
public ApplicationUser ApplicationCreatedUser { get; set; }
[ForeignKey("LastModifiedBy")]
public ApplicationUser ApplicationLastModifiedUser { get; set; }
}
}
在我们的Razor页面中，我们可以通过以下操作删除包含TournamentBatchItem的TournamentBatch：
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.RazorPages;
using Microsoft.EntityFrameworkCore;
using AthlosifyWebArchery.Data;
using AthlosifyWebArchery.Models;
using Microsoft.Extensions.Logging;
namespace AthlosifyWebArchery.Pages.Administrators.TournamentBatches
{
public class DeleteModel : PageModel
{
private readonly AthlosifyWebArchery.Data.ApplicationDbContext _context;
private readonly ILogger _logger;
public DeleteModel(AthlosifyWebArchery.Data.ApplicationDbContext context,
ILogger<DeleteModel> logger)
{
_context = context;
_logger = logger;
}
[BindProperty]
public TournamentBatch TournamentBatch { get; set; }
public IList<TournamentBatchItem> tournamentBatchItems { get; set; }
public string ConcurrencyErrorMessage { get; set; }
public async Task<IActionResult> OnGetAsync(Guid? id, bool? concurrencyError)
{
if (id == null)
{
return NotFound();
}
TournamentBatch = await _context.TournamentBatch
.AsNoTracking() //Addded
.FirstOrDefaultAsync(m => m.TournamentBatchID == id);
if (TournamentBatch == null)
{
return NotFound();
}
if (concurrencyError.GetValueOrDefault())
{
ConcurrencyErrorMessage = "The record you attempted to delete "
+ "was modified by another user after you selected delete. "
+ "The delete operation was canceled and the current values in the "
+ "database have been displayed. If you still want to delete this "
+ "record, click the Delete button again.";
}
return Page();
}
public async Task<IActionResult> OnPostAsync(Guid? id)
{
try
{
//var tournamentBatchItems = await _context.TournamentBatchItem.Where(m => m.TournamentBatchID == id).ToListAsync();
//_context.TournamentBatchItem.RemoveRange(tournamentBatchItems);
//await _context.SaveChangesAsync();
if (await _context.TournamentBatch.AnyAsync(
m => m.TournamentBatchID == id))
{
// Department.rowVersion value is from when the entity
// was fetched. If it doesn't match the DB, a
// DbUpdateConcurrencyException exception is thrown.
_context.TournamentBatch.Remove(TournamentBatch);
_logger.LogInformation($"TournamentBatch.BeforeSaveChangesAsync ... ");
await _context.SaveChangesAsync();
_logger.LogInformation($"DbInitializer.AfterSaveChangesAsync ... ");
}
return RedirectToPage("./Index");
}
catch(DbUpdateException)
{
return RedirectToPage("./Delete",
new { concurrencyError = true, id = id });
}
//catch (DbUpdateConcurrencyException)
//{
// return RedirectToPage("./Delete",
// new { concurrencyError = true, id = id });
//}
}
}
}
...，并且出现以下错误，这有点奇怪。
System.Data.SqlClient.SqlException（0x80131904）：UPDATE语句 与FOREIGN KEY约束冲突 “ FK_TournamentBatch_Host_HostID”。数据库中发生了冲突 “ aspnet-AthlosifyWebArchery-53bc9b9d-9d6a-45d4-8429-2a2761773502”， 表“ dbo.Host”的“ HostID”列。该声明已终止。
有什么想法吗？
我们所做的事情：
如果我们从OnBeforeSaving();方法中删除了SaveChangesAsyc()，则该代码将成功删除（硬删除） TournamentBatch和TournamentBatchItem。
如果我们从OnBeforeSaving();方法中加入了SaveChangesAsyc()，并通过删除 Host 和 TournamentBatchItem （不是 TournamentBatch < / strong>），则代码已成功删除（软删除）。
似乎与Host和TournamentBatch之间的关系有关
环境：
答案 0 :(得分：2)
您可以尝试以下方法并更改实现软删除的方式。
在您的ApplicationDBContext OnBeforeSaving方法中更改以下代码
foreach (var entry in ChangeTracker.Entries()
.Where(e => e.State == EntityState.Deleted &&
e.Metadata.GetProperties().Any(x => x.Name == "IsDeleted")))
{
switch (entry.State)
{
case EntityState.Added:
entry.CurrentValues["IsDeleted"] = false;
break;
case EntityState.Deleted:
entry.State = EntityState.Modified;
entry.CurrentValues["IsDeleted"] = true;
break;
}
}
----到-----
foreach (var entry in ChangeTracker.Entries()
.Where(e => e.State == EntityState.Deleted &&
e.Metadata.GetProperties().Any(x => x.Name == "IsDeleted")))
{
SoftDelete(entry);
}
SoftDelete方法：
private void SoftDelete(DbEntityEntry entry)
{
Type entryEntityType = entry.Entity.GetType();
string tableName = GetTableName(entryEntityType);
string primaryKeyName = GetPrimaryKeyName(entryEntityType);
string sql =
string.Format(
"UPDATE {0} SET IsDeleted = true WHERE {1} = @id",
tableName, primaryKeyName);
Database.ExecuteSqlCommand(
sql,
new SqlParameter("@id", entry.OriginalValues[primaryKeyName]));
// prevent hard delete
entry.State = EntityState.Detached;
}
此方法将对每个删除的实体执行sql查询：
UPDATE TournamentBatch SET IsDeleted = true WHERE TournamentBatchID = 123
要使其具有通用性并与任何实体（不仅仅是TournamentBatch）兼容，我们需要知道两个附加属性，表名称和主键名称
为此目的，SoftDelete方法内部有两个函数：GetTableName和GetPrimaryKeyName。我已经在单独的文件中定义了它们，并将类标记为局部。因此，请确保使上下文类成为局部类，以使事情正常进行。这是具有缓存机制的GetTableName和GetPrimaryKeyName：
public partial class ApplicationDBContext
{
private static Dictionary<Type, EntitySetBase> _mappingCache =
new Dictionary<Type, EntitySetBase>();
private string GetTableName(Type type)
{
EntitySetBase es = GetEntitySet(type);
return string.Format("[{0}].[{1}]",
es.MetadataProperties["Schema"].Value,
es.MetadataProperties["Table"].Value);
}
private string GetPrimaryKeyName(Type type)
{
EntitySetBase es = GetEntitySet(type);
return es.ElementType.KeyMembers[0].Name;
}
private EntitySetBase GetEntitySet(Type type)
{
if (!_mappingCache.ContainsKey(type))
{
ObjectContext octx = ((IObjectContextAdapter)this).ObjectContext;
string typeName = ObjectContext.GetObjectType(type).Name;
var es = octx.MetadataWorkspace
.GetItemCollection(DataSpace.SSpace)
.GetItems<EntityContainer>()
.SelectMany(c => c.BaseEntitySets
.Where(e => e.Name == typeName))
.FirstOrDefault();
if (es == null)
throw new ArgumentException("Entity type not found in GetTableName", typeName);
_mappingCache.Add(type, es);
}
return _mappingCache[type];
}
}
答案 1 :(得分：1)
原因
我想原因是您从客户端绑定了TournamentBatch。
让我们回顾一下OnPostAsync()方法：
public async Task<IActionResult> OnPostAsync(Guid? id)
{
try
{
if (await _context.TournamentBatch.AnyAsync(
m => m.TournamentBatchID == id))
{
_context.TournamentBatch.Remove(TournamentBatch);
_logger.LogInformation($"TournamentBatch.BeforeSaveChangesAsync ... ");
await _context.SaveChangesAsync();
_logger.LogInformation($"DbInitializer.AfterSaveChangesAsync ... ");
}
return RedirectToPage("./Index");
}
// ....
}
在这里 TournamentBatch是PageModel的属性：
[BindProperty]
public Models.TournamentBatch TournamentBatch{ get; set; }
请注意您没有根据ID从数据库中检索到它，而您只是直接通过_context.TournamentBatch.Remove(TournamentBatch);将其删除了。
换句话说，TournamentBatch的其他属性将由ModelBinding设置。假设如果您仅提交ID，则所有其他属性均为默认值。例如，Host将为空，而HostID将是默认的00000000-0000-0000-0000-000000000000。因此，当您保存更改时，EF Core将更新模型，如下所示：
UPDATE [TournamentBatch]
SET [HostID] = '00000000-0000-0000-0000-000000000000' ,
[IsDeleted] = 1 ,
# ... other fields
WHERE [TournamentBatchID] = 'A6F5002A-60CA-4B45-D343-08D660167B06'
由于没有ID为00000000-0000-0000-0000-000000000000的Host记录，数据库将抱怨：
UPDATE语句与FOREIGN KEY约束“ FK_TournamentBatch_Host_HostID”冲突。在数据库“ App-93a194ca-9622-487c-94cf-bcbe648c6556”的表“ dbo.Host”的“ Id”列中发生了冲突。 该声明已终止。
如何修复
您需要通过TournamentBatch从服务器检索TournamentBatch而不是从客户端绑定TournamentBatch = await _context.TournamentBatch.FindAsync(id);。因此，您将正确设置所有属性，以便EF可以正确更新字段：
try
{
//var tournamentBatchItems = await _context.TournamentBatchItem.Where(m => m.TournamentBatchID == id).ToListAsync();
//_context.TournamentBatchItem.RemoveRange(tournamentBatchItems);
//await _context.SaveChangesAsync();
TournamentBatch = await _context.TournamentBatch.FindAsync(id);
if (TournamentBatch != null)
{
// Department.rowVersion value is from when the entity
// was fetched. If it doesn't match the DB, a
// DbUpdateConcurrencyException exception is thrown.
_context.TournamentBatch.Remove(TournamentBatch);
_logger.LogInformation($"TournamentBatch.BeforeSaveChangesAsync ... ");
await _context.SaveChangesAsync();
_logger.LogInformation($"DbInitializer.AfterSaveChangesAsync ... ");
}
return RedirectToPage("./Index");
}
// ...
答案 2 :(得分：0)
不要忘记外键是对另一个表中唯一值的引用。如果存在外键，SQL将确保引用完整性，因此它不允许您使用孤立的键引用。
在外键列中插入值时，该值必须为null或对另一个表中某行的现有引用，并且在删除时，必须先删除包含外键的行，然后再删除该行参考。
如果不这样做，您将得到一条错误提示。
因此，首先将行输入到“主”表中，然后再输入“相关”表信息。
答案 3 :(得分：0)
在EF中更新与主键或外键有关的任何内容时，通常都会引发错误。可以fix this manually。
但是，我个人要做的是删除整个数据库，添加迁移并更新数据库。如果我有很多测试数据，可能会生成一个插入脚本。 （这显然在生产环境中不起作用，但是再次重申，无论如何，您都不应该在生产环境中更改数据库，而是添加带有时间戳的可空列，该时间戳指示删除的时间；如果其处于活动状态，则为null记录。）