C# 实体框架核心-更新时CreatedTime为Null

我希望使用实体框架核心自动创建和修改字段。我在中找到了一个解决方案，并遵循了这一点

它非常适合添加数据-

但若我试图更新数据（更新时间是完美的，但创建时间为空），那个么我就会遇到这样的问题-

public class BaseEntity
{
    [Key]
    public long Id { get; set; }

    [DataType(DataType.Date), DisplayFormat(DataFormatString = "{0:yyyy-MM-dd HH:mm:ss.fff}", ApplyFormatInEditMode = true)]
    public DateTime? CreatedTime { get; set; }
    public long CreatorUserId { get; set; }
    //public string CreatorIPAddress { get; set; }

    [DataType(DataType.Date), DisplayFormat(DataFormatString = "{0:yyyy-MM-dd HH:mm:ss.fff}", ApplyFormatInEditMode = true)]
    public DateTime? LastModifiedTime { get; set; }
    public long LastModifireUserId { get; set; }
    //public string LastModifireIPAddress { get; set; }
}

public class ApplicationDbContext : DbContext
{
    //List all tables here
    public DbSet<Advertisement> Advertisements { get; set; }
    public DbSet<Address> Addresses { get; set; }
    public DbSet<Country> Countries { get; set; }
    public DbSet<EducationResult> EducationResults { get; set; }
    public DbSet<Experience> Experiences { get; set; }
    public DbSet<JobCircular> JobCirculars { get; set; }
    public DbSet<Language> Languages { get; set; }
    public DbSet<Reference> References { get; set; }
    public DbSet<Research> Researches { get; set; }
    public DbSet<ResearchDegree> ResearchDegrees { get; set; }
    public DbSet<TeacherApplication> TeacherApplications { get; set; }
    public DbSet<Training> Trainings { get; set; }

    //Configure Database Settings
    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        //Configuration.GetConnectionString("DefaultConnection");
        optionsBuilder.UseSqlite("Filename=./applicationDB.db");
    }

    public override int SaveChanges()
    {
        AddTimestamps();
        return base.SaveChanges();
    }

    public override int SaveChanges(bool acceptAllChangesOnSuccess)
    {
        AddTimestamps();
        return base.SaveChanges(acceptAllChangesOnSuccess);
    }

    public override Task<int> SaveChangesAsync(CancellationToken cancellationToken = default(CancellationToken))
    {
        AddTimestamps();
        return base.SaveChangesAsync(cancellationToken);
    }

    public override Task<int> SaveChangesAsync(bool acceptAllChangesOnSuccess, CancellationToken cancellationToken = default(CancellationToken))
    {
        AddTimestamps();
        return base.SaveChangesAsync(acceptAllChangesOnSuccess, cancellationToken);
    }

    private void AddTimestamps()
    {
        var entities = ChangeTracker.Entries().Where(x => x.Entity is BaseEntity && (x.State == EntityState.Added || x.State == EntityState.Modified));

        /*
        var currentUsername = !string.IsNullOrEmpty(System.Web.HttpContext.Current?.User?.Identity?.Id)
            ? HttpContext.Current.User.Identity.Id
            : -1;   //-1 for Anonimous
        */
        long currentUserId = -1;    //-1 for Anonimous

        foreach (var entity in entities)
        {
            if (entity.State == EntityState.Added)
            {
                ((BaseEntity)entity.Entity).CreatedTime = DateTime.UtcNow;
                ((BaseEntity)entity.Entity).CreatorUserId = currentUserId;
                //((BaseEntity)entity.Entity).CreatorIPAddress = HttpContext.Connection.RemoteIpAddress.ToString();
            }
            else
            {
                ((BaseEntity)entity.Entity).CreatedTime = ((BaseEntity)entity.Entity).CreatedTime;
                ((BaseEntity)entity.Entity).CreatorUserId = ((BaseEntity)entity.Entity).CreatorUserId;
                //((BaseEntity)entity.Entity).CreatorIPAddress = ((BaseEntity)entity.Entity).CreatorIPAddress;
            }

            ((BaseEntity)entity.Entity).LastModifiedTime = DateTime.UtcNow;
            ((BaseEntity)entity.Entity).LastModifireUserId = currentUserId;
            //((BaseEntity)entity.Entity).LastModifireIPAddress = HttpContext.Connection.RemoteIpAddress.ToString();
        }
    }

    public DbSet<ApplicationManagement.DbModel.Office> Office { get; set; }
}

因此，创建属性丢失（设置为Null）

我的BaseEntity类是这样的-

public class BaseEntity
{
    [Key]
    public long Id { get; set; }

    [DataType(DataType.Date), DisplayFormat(DataFormatString = "{0:yyyy-MM-dd HH:mm:ss.fff}", ApplyFormatInEditMode = true)]
    public DateTime? CreatedTime { get; set; }
    public long CreatorUserId { get; set; }
    //public string CreatorIPAddress { get; set; }

    [DataType(DataType.Date), DisplayFormat(DataFormatString = "{0:yyyy-MM-dd HH:mm:ss.fff}", ApplyFormatInEditMode = true)]
    public DateTime? LastModifiedTime { get; set; }
    public long LastModifireUserId { get; set; }
    //public string LastModifireIPAddress { get; set; }
}

public class ApplicationDbContext : DbContext
{
    //List all tables here
    public DbSet<Advertisement> Advertisements { get; set; }
    public DbSet<Address> Addresses { get; set; }
    public DbSet<Country> Countries { get; set; }
    public DbSet<EducationResult> EducationResults { get; set; }
    public DbSet<Experience> Experiences { get; set; }
    public DbSet<JobCircular> JobCirculars { get; set; }
    public DbSet<Language> Languages { get; set; }
    public DbSet<Reference> References { get; set; }
    public DbSet<Research> Researches { get; set; }
    public DbSet<ResearchDegree> ResearchDegrees { get; set; }
    public DbSet<TeacherApplication> TeacherApplications { get; set; }
    public DbSet<Training> Trainings { get; set; }

    //Configure Database Settings
    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        //Configuration.GetConnectionString("DefaultConnection");
        optionsBuilder.UseSqlite("Filename=./applicationDB.db");
    }

    public override int SaveChanges()
    {
        AddTimestamps();
        return base.SaveChanges();
    }

    public override int SaveChanges(bool acceptAllChangesOnSuccess)
    {
        AddTimestamps();
        return base.SaveChanges(acceptAllChangesOnSuccess);
    }

    public override Task<int> SaveChangesAsync(CancellationToken cancellationToken = default(CancellationToken))
    {
        AddTimestamps();
        return base.SaveChangesAsync(cancellationToken);
    }

    public override Task<int> SaveChangesAsync(bool acceptAllChangesOnSuccess, CancellationToken cancellationToken = default(CancellationToken))
    {
        AddTimestamps();
        return base.SaveChangesAsync(acceptAllChangesOnSuccess, cancellationToken);
    }

    private void AddTimestamps()
    {
        var entities = ChangeTracker.Entries().Where(x => x.Entity is BaseEntity && (x.State == EntityState.Added || x.State == EntityState.Modified));

        /*
        var currentUsername = !string.IsNullOrEmpty(System.Web.HttpContext.Current?.User?.Identity?.Id)
            ? HttpContext.Current.User.Identity.Id
            : -1;   //-1 for Anonimous
        */
        long currentUserId = -1;    //-1 for Anonimous

        foreach (var entity in entities)
        {
            if (entity.State == EntityState.Added)
            {
                ((BaseEntity)entity.Entity).CreatedTime = DateTime.UtcNow;
                ((BaseEntity)entity.Entity).CreatorUserId = currentUserId;
                //((BaseEntity)entity.Entity).CreatorIPAddress = HttpContext.Connection.RemoteIpAddress.ToString();
            }
            else
            {
                ((BaseEntity)entity.Entity).CreatedTime = ((BaseEntity)entity.Entity).CreatedTime;
                ((BaseEntity)entity.Entity).CreatorUserId = ((BaseEntity)entity.Entity).CreatorUserId;
                //((BaseEntity)entity.Entity).CreatorIPAddress = ((BaseEntity)entity.Entity).CreatorIPAddress;
            }

            ((BaseEntity)entity.Entity).LastModifiedTime = DateTime.UtcNow;
            ((BaseEntity)entity.Entity).LastModifireUserId = currentUserId;
            //((BaseEntity)entity.Entity).LastModifireIPAddress = HttpContext.Connection.RemoteIpAddress.ToString();
        }
    }

    public DbSet<ApplicationManagement.DbModel.Office> Office { get; set; }
}

而DbContext类是这样的-

public class BaseEntity
{
    [Key]
    public long Id { get; set; }

    [DataType(DataType.Date), DisplayFormat(DataFormatString = "{0:yyyy-MM-dd HH:mm:ss.fff}", ApplyFormatInEditMode = true)]
    public DateTime? CreatedTime { get; set; }
    public long CreatorUserId { get; set; }
    //public string CreatorIPAddress { get; set; }

    [DataType(DataType.Date), DisplayFormat(DataFormatString = "{0:yyyy-MM-dd HH:mm:ss.fff}", ApplyFormatInEditMode = true)]
    public DateTime? LastModifiedTime { get; set; }
    public long LastModifireUserId { get; set; }
    //public string LastModifireIPAddress { get; set; }
}

public class ApplicationDbContext : DbContext
{
    //List all tables here
    public DbSet<Advertisement> Advertisements { get; set; }
    public DbSet<Address> Addresses { get; set; }
    public DbSet<Country> Countries { get; set; }
    public DbSet<EducationResult> EducationResults { get; set; }
    public DbSet<Experience> Experiences { get; set; }
    public DbSet<JobCircular> JobCirculars { get; set; }
    public DbSet<Language> Languages { get; set; }
    public DbSet<Reference> References { get; set; }
    public DbSet<Research> Researches { get; set; }
    public DbSet<ResearchDegree> ResearchDegrees { get; set; }
    public DbSet<TeacherApplication> TeacherApplications { get; set; }
    public DbSet<Training> Trainings { get; set; }

    //Configure Database Settings
    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        //Configuration.GetConnectionString("DefaultConnection");
        optionsBuilder.UseSqlite("Filename=./applicationDB.db");
    }

    public override int SaveChanges()
    {
        AddTimestamps();
        return base.SaveChanges();
    }

    public override int SaveChanges(bool acceptAllChangesOnSuccess)
    {
        AddTimestamps();
        return base.SaveChanges(acceptAllChangesOnSuccess);
    }

    public override Task<int> SaveChangesAsync(CancellationToken cancellationToken = default(CancellationToken))
    {
        AddTimestamps();
        return base.SaveChangesAsync(cancellationToken);
    }

    public override Task<int> SaveChangesAsync(bool acceptAllChangesOnSuccess, CancellationToken cancellationToken = default(CancellationToken))
    {
        AddTimestamps();
        return base.SaveChangesAsync(acceptAllChangesOnSuccess, cancellationToken);
    }

    private void AddTimestamps()
    {
        var entities = ChangeTracker.Entries().Where(x => x.Entity is BaseEntity && (x.State == EntityState.Added || x.State == EntityState.Modified));

        /*
        var currentUsername = !string.IsNullOrEmpty(System.Web.HttpContext.Current?.User?.Identity?.Id)
            ? HttpContext.Current.User.Identity.Id
            : -1;   //-1 for Anonimous
        */
        long currentUserId = -1;    //-1 for Anonimous

        foreach (var entity in entities)
        {
            if (entity.State == EntityState.Added)
            {
                ((BaseEntity)entity.Entity).CreatedTime = DateTime.UtcNow;
                ((BaseEntity)entity.Entity).CreatorUserId = currentUserId;
                //((BaseEntity)entity.Entity).CreatorIPAddress = HttpContext.Connection.RemoteIpAddress.ToString();
            }
            else
            {
                ((BaseEntity)entity.Entity).CreatedTime = ((BaseEntity)entity.Entity).CreatedTime;
                ((BaseEntity)entity.Entity).CreatorUserId = ((BaseEntity)entity.Entity).CreatorUserId;
                //((BaseEntity)entity.Entity).CreatorIPAddress = ((BaseEntity)entity.Entity).CreatorIPAddress;
            }

            ((BaseEntity)entity.Entity).LastModifiedTime = DateTime.UtcNow;
            ((BaseEntity)entity.Entity).LastModifireUserId = currentUserId;
            //((BaseEntity)entity.Entity).LastModifireIPAddress = HttpContext.Connection.RemoteIpAddress.ToString();
        }
    }

    public DbSet<ApplicationManagement.DbModel.Office> Office { get; set; }
}

公共类ApplicationDbContext:DbContext
{
//在此列出所有表格
公共数据库集播发{get；set；}
公共数据库集地址{get；set；}
公共数据库集国家{get；set；}
公共数据库集教育结果{get；set；}
公共数据库集{get；set；}
公共DbSet作业循环{get；set；}
公共数据库集语言{get；set；}
公共数据库集引用{get；set；}
公共数据库集{get；set；}
公共DbSet ResearchDegrees{get；set；}
公共DbSet教学应用程序{get；set；}
公共数据库集{get；set；}
//配置数据库设置
配置时受保护的覆盖无效（DBContextOptions Builder Options Builder）
{
//GetConnectionString（“DefaultConnection”）；
optionsBuilder.UseSqlite（“文件名=./applicationDB.db”）；
}
公共覆盖int SaveChanges（）
{
AddTimestamps（）；
返回base.SaveChanges（）；
}
公共覆盖int SaveChanges（bool acceptAllChangesOnSuccess）
{
AddTimestamps（）；
返回base.SaveChanges（AcceptalChangesOnSuccess）；
}
公共覆盖任务saveChangesSync（CancellationToken CancellationToken=默认值（CancellationToken））
{
AddTimestamps（）；
返回base.saveChangesSync（cancellationToken）；
}
public override Task savechangesync（bool acceptillchangesonsuccess，CancellationToken CancellationToken=default（CancellationToken））
{
AddTimestamps（）；
return base.saveChangesSync（acceptAllChangesOnSuccess，cancellationToken）；
}
私有void AddTimestamps（）
{
var entities=ChangeTracker.Entries（）。其中（x=>x.Entity为BaseEntity&（x.State==EntityState.Added | | x.State==EntityState.Modified））；
/*
var currentUsername=！string.IsNullOrEmpty（System.Web.HttpContext.Current？.User？.Identity？.Id）
？HttpContext.Current.User.Identity.Id
：-1；//-1表示一个动物
*/
长currentUserId=-1；//-1表示匿名
foreach（实体中的var实体）
{
if（entity.State==EntityState.Added）
{
（（BaseEntity）entity.entity）.CreatedTime=DateTime.UtcNow；
（（BaseEntity）entity.entity）.CreatorUserId=currentUserId；
//（（BaseEntity）entity.entity.CreatorIPAddress=HttpContext.Connection.RemoteIpAddress.ToString（）；
}
其他的
{
（（BaseEntity）entity.entity.CreatedTime=（（BaseEntity）entity.entity.CreatedTime；
（（BaseEntity）entity.entity.CreatorUserId=（（BaseEntity）entity.entity.CreatorUserId；
//（（BaseEntity）entity.entity.CreatorIPAddress=（（BaseEntity）entity.entity.CreatorIPAddress；
}
（（BaseEntity）entity.entity.LastModifiedTime=DateTime.UtcNow；
（（BaseEntity）entity.entity）.LastModifireUserId=currentUserId；
//（（BaseEntity）entity.entity.LastModifireIPAddress=HttpContext.Connection.RemoteIpAddress.ToString（）；
}
}
公共数据库集办公室{get；set；}
}

---

有人能帮忙吗？

造成这种情况的唯一方法是使用实体模型作为视图模型。因此，您从表单或通过设置了两个属性的API调用发布一个实体，而不是

CreatedTime

或

CreatorUserId

，从而使它们获得默认值

null

然后将这些空值指定给加载的实体，并覆盖它们

可以通过使用viewmodels并将适当的属性映射到加载的实体来防止这种情况：

// somewhere in a controller
public void UpdatePerson(UpdatePersonViewModel model)
{
    var entity = Get(model.Id);

    entity.Name = model.Name;

    Save(entity);
}

---

或者对实体而不是viewmodel执行相同的操作，我不建议这样做。

导致这种情况的唯一方法是将实体模型用作视图模型。因此，您从表单或通过设置了两个属性的API调用发布一个实体，而不是

CreatedTime

或

CreatorUserId

，从而使它们获得默认值

null

然后将这些空值指定给加载的实体，并覆盖它们

可以通过使用viewmodels并将适当的属性映射到加载的实体来防止这种情况：

// somewhere in a controller
public void UpdatePerson(UpdatePersonViewModel model)
{
    var entity = Get(model.Id);

    entity.Name = model.Name;

    Save(entity);
}

---

或者对实体而不是viewmodel执行相同的操作，我不建议这样做。

从逻辑上讲，对于修改状态，创建时间将保持原始创建时间。下面是获取原始值FOMDB的脚本

((BaseEntity)entity.Entity).CreatedTime = entity.Property("CreatedTime").OriginalValue;

---

从逻辑上讲，对于修改后的状态，创建时间将保持原始创建时间。下面是获取原始值FOMDB的脚本

((BaseEntity)entity.Entity).CreatedTime = entity.Property("CreatedTime").OriginalValue;

---

你真的需要这个代码吗

else
{
（（BaseEntity）entity.entity.CreatedTime=（（BaseEntity）entity.entity.CreatedTime；
（（BaseEntity）entity.entity.CreatorUserId=（（BaseEntity）entity.entity.CreatorUserId；
//（（BaseEntity）entity.entity.CreatorIPAddress=（（BaseEntity）entity.entity.CreatorIPAddress；
}

您真的需要此代码吗

else
{
（（BaseEntity）entity.entity.CreatedTime=（（BaseEntity）entity.entity.CreatedTime；
（（BaseEntity）entity.entity.CreatorUserId=（（BaseEntity）entity.entity.CreatorUserId；
//（（BaseEntity）entity.entity.CreatorIPAddress=（（BaseEntity）entity.entity.CreatorIPAddress；
}

我使用实体模型作为视图模型。FWIW，aut只需要这样的东西