如何自动填充 CreatedDate 和 ModifiedDate？

Question

我正在学习 ASP.NET Core MVC，我的模型是

namespace Joukyuu.Models
{
    public class Passage
    {
        public int PassageId { get; set; }
        public string Contents { get; set; }


        public DateTime CreatedDate { get; set; }
        public DateTime ModifiedDate { get; set; }
    }
}

Passage 表用于保存我写的段落。

场景

• Create 视图只有一个字段Contents 用于输入段落。 CreatedDate 和 ModifiedDate 必须由服务器自动设置为相等（使用 UTC 格式）。

• Edit 视图只有一个字段Contents 用于编辑段落。 ModifiedDate 必须由服务器自动设置。

问题

我必须将哪些属性附加到CreatedDate 和ModifiedDate 属性才能使它们根据上述情况由服务器自动填充？

Answer 1

我必须将哪些属性附加到 CreatedDate 和 ModifiedDate 属性以使它们根据上述情况由服务器自动填充？

解决方案 1)

namespace Joukyuu.Models
{
    public class Passage
    {
        public int PassageId { get; set; }
        public string Contents { get; set; }


        public DateTime CreatedDate { get; set; }
        public DateTime ModifiedDate { get; set; }

       public Passage()
       {          
         this.CreatedDate  = DateTime.UtcNow;
         this.ModifiedDate = DateTime.UtcNow;
       }
    }
}

通过编辑，您必须自己更改/更新它！

解决方案 2)

自定义属性：

[SqlDefaultValue(DefaultValue = "getutcdate()")]
public DateTime CreatedDate { get; set; }

Entity Framework 6 Code first Default value

解决方案 3)

在计算的帮助下：

[Required, DatabaseGenerated(DatabaseGeneratedOption.Computed)]
public DateTime CreatedUtc { get; set; 


  "dbo.Products",
            c => new
                {
                    ProductId = c.Int(nullable: false, identity: true),
                    Name = c.String(),
                    CreatedUtc = c.DateTime(nullable: false, defaultValueSql: "GETUTCDATE()"),
                })
            .PrimaryKey(t => t.ProductId);

https://andy.mehalick.com/2014/02/06/ef6-adding-a-created-datetime-column-automatically-with-code-first-migrations/

解决方案 4) 您也可以通过手动修改查询来使用命令拦截器来做到这一点。

解决方案 5) 使用 Repository 模式管理数据创建并由 CreateNew 设置 这是我喜欢的解决方案！

https://msdn.microsoft.com/en-us/library/ff649690.aspx

解决方案 6) 只需在 UI 或 VM 中设置或进入。

---

在Entity Framework Core 1.0中很容易：

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<Passage>()
        .Property(b => b.CreatedDate )
        .HasDefaultValueSql("getdate()");
}

Answer 2

对于使用异步系统（SaveChangesAsync）和.NET Core的用户，最好重写DbContext的SaveChangesAsync方法：

public override Task<int> SaveChangesAsync(
    bool acceptAllChangesOnSuccess,
    CancellationToken cancellationToken = default(CancellationToken))
{
    var AddedEntities = ChangeTracker.Entries()
        .Where(E => E.State == EntityState.Added)
        .ToList();

    AddedEntities.ForEach(E =>
    {
        E.Property("CreationTime").CurrentValue = DateTime.Now;
    });

    var EditedEntities = ChangeTracker.Entries()
        .Where(E => E.State == EntityState.Modified)
        .ToList();

    EditedEntities.ForEach(E =>
    {
        E.Property("ModifiedDate").CurrentValue = DateTime.Now;
    });

    return base.SaveChangesAsync(acceptAllChangesOnSuccess, cancellationToken);
}

此外，您可以使用以下属性为模型定义基类或接口：

public class SaveConfig
{
    public DateTime CreationTime { get; set; }
    public DateTime? ModifiedDate { get; set; }
}

Answer 3

如果您使用的是代码优先，您可以试试这个

[Required, DatabaseGenerated(DatabaseGeneratedOption.Computed)]
public DateTime CreatedDate { get; set; }

关于迁移

AddColumn("Passage", "CreatedDate", n => n.DateTime(nullable: false, defaultValueSql: "GETDATE()"));

更多参考here,similar answer

或者您可以全局覆盖saveChanges 注意*如果您有CreatedDate 字段，这将影响整个模型

public override int SaveChanges()
{
  DateTime saveTime = DateTime.Now;
  foreach (var entry in this.ChangeTracker.Entries()
      .Where(e => e.State == (EntityState) System.Data.EntityState.Added))
   {
     if (entry.Property("CreatedDate").CurrentValue == null)
       entry.Property("CreatedDate").CurrentValue = saveTime;
   }
   return base.SaveChanges();  
}

Answer 4

PostgreSQL中CreationDate的解决方案：

builder.Property(e => e.CreationDate)
  .HasColumnType("timestamp without time zone")
  .HasDefaultValueSql("NOW()")
  .ValueGeneratedOnAdd();

通过：https://www.npgsql.org/efcore/modeling/generated-properties.html#guiduuid-generation 不幸的是没有更新事件的解决方案

Answer 5

使用 SaveChangesAsync 的替代方法是您可以为相应的数据库创建数据库触发器。我为 mssql、postgress、sqlite 和 mysql 制作了一个带有一些辅助函数的 gist。这是代码的粘贴。

有一个有趣的讨论here 具有数据库逻辑与应用程序逻辑。就个人而言，让数据库强制执行 updated_date 列更新在我的代码中的行数更少。他们还提出的一个论点是，如果使用不同的服务更改了您的数据库，这些数据库完整性约束仍将适用于数据库级别。

每当我进行核心数据迁移以在表和列更新上添加自定义更新列触发器时，我一直在使用下面的这个类。

using Microsoft.EntityFrameworkCore.Metadata;
using Npgsql.EntityFrameworkCore.PostgreSQL.Metadata;

namespace ProjectNamespace.Api.Utils
{
    public class DatabaseTools
    {
        public class DatabaseKeys
        {
            public string ValueGenerationStrategy;
            public object SerialColumn;
            public string DEFAULTDATE_CREATE;
            public string DEFAULTDATE_UPDATE;
            public string dateTime;
            public bool UpdateDateTrigger = true;
            public string ProviderName { get; set; }
        }
        /*
        Notes:
        can check if updateDateTrigger needed for dataprovider and add update triggers
        if (dbKeys.UpdateDateTrigger)
            {
                migrationBuilder.Sql(DatabaseTools.getUpdateDateTrigger(dbKeys.ProviderName, "TG_roles_updated_at", "roles", "updated_at"));
            }
        if postgress don't forget to drop the generated functions for each of the different named update columns (updated_at, modified_date) at the end of the migration E.g.
        protected override void Down(MigrationBuilder migrationBuilder){...
        if (dbKeys.ProviderName == "postgress")
            {
                migrationBuilder.Sql(@"
                    DROP FUNCTION update_" + "updated_at" + @"_column();
                    ");
            }
        postgres doesn't support parameters in triggers for new and old keywords.
         */
        /// <summary>
        /// needed for non mysql implementation to update a datetime on a record update
        /// </summary>
        /// <param name="databaseProvider"></param>
        /// <param name="name"></param>
        /// <param name="table"></param>
        /// <param name="column"></param>
        /// <param name="schema"></param>
        /// <param name="id_column"></param>
        /// <returns></returns>
        public static string getUpdateDateTrigger(string databaseProvider, string name, string table, string column, string schema = "", string id_column = "id")
        {
            string updateDateTrigger = null;
            if (!string.IsNullOrEmpty(schema))
                schema = schema + ".";
            switch (databaseProvider)
            {
                case "sqlite":
                    updateDateTrigger = @"
                    CREATE TRIGGER [" + name + @"]  
                        AFTER   
                        UPDATE  
                        ON " + table + @"
                        FOR EACH ROW   
                        WHEN NEW." + column + @" <= OLD." + column + @"  
                    BEGIN  
                        update " + table + @" set " + column + @"=CURRENT_TIMESTAMP where " + id_column + @"=OLD." + id_column + @";  
                    END  
                    ";
                    break;
                case "postgress":
                    updateDateTrigger = @"
                    CREATE OR REPLACE FUNCTION update_" + column + @"_column() RETURNS TRIGGER AS
                    $$
                    BEGIN
                        NEW.""" + column + @""" = now();
                        RETURN NEW;  
                    END;
                    $$ LANGUAGE plpgsql;
                    CREATE TRIGGER " + name + @" 
                    BEFORE UPDATE ON " + schema + @"""" + table + @"""
                    FOR EACH ROW EXECUTE PROCEDURE update_" + column + @"_column();
                    ";
                    break;
                case "sqlserver":
                    updateDateTrigger = @"
                    CREATE TRIGGER " + name + @" 
                    ON " + table + @"
                    AFTER UPDATE AS
                        UPDATE " + table + @"
                        SET " + column + @" = GETDATE()
                        WHERE " + id_column + @" IN (SELECT DISTINCT " + id_column + @" FROM Inserted);
                    ";
                    break;
            }

            return updateDateTrigger;
        }
        /*
        Notes:
        if in OnModelCreating can call as var dbKeys = DatabaseTools.getDatabaseDefaults(this.Database.ProviderName);
        if in a migration call as var dbKeys = DatabaseTools.getDatabaseDefaults(migrationBuilder.ActiveProvider);
        Then update any datetime columns for correct defaults
        created_at = table.Column<DateTime>(type: dbKeys.dateTime, nullable: true, defaultValueSql: dbKeys.DEFAULTDATE_CREATE),
        updated_at = table.Column<DateTime>(type: dbKeys.dateTime, nullable: true, defaultValueSql: dbKeys.DEFAULTDATE_UPDATE)
         */
        /// <summary>
        /// Can get specific formats for different databases. Supports mssql, postgress, sqlite, and mysql.
        /// </summary>
        /// <param name="databaseProvider"></param>
        /// <returns></returns>
        public static DatabaseKeys getDatabaseDefaults(string databaseProvider)
        {
            var dbKeys = new DatabaseKeys();
            dbKeys.dateTime = "datetime";

            switch (databaseProvider)
            {
                case "Microsoft.EntityFrameworkCore.Sqlite":
                case "sqlite":
                    dbKeys.DEFAULTDATE_UPDATE = "datetime('now')";
                    dbKeys.SerialColumn = true;
                    dbKeys.ProviderName = "sqlite";
                    dbKeys.ValueGenerationStrategy = "Sqlite:Autoincrement";
                    break;
                case "postgress":
                case "Npgsql.EntityFrameworkCore.PostgreSQL":
                    dbKeys.DEFAULTDATE_UPDATE = "CURRENT_TIMESTAMP";
                    dbKeys.SerialColumn = NpgsqlValueGenerationStrategy.SerialColumn;
                    dbKeys.ProviderName = "postgress";
                    dbKeys.ValueGenerationStrategy = "Npgsql:ValueGenerationStrategy";
                    dbKeys.dateTime = "timestamp";
                    break;
                case "mysql":
                case "MySql.Data.EntityFrameworkCore":
                    dbKeys.DEFAULTDATE_UPDATE = "CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP";
                    dbKeys.DEFAULTDATE_CREATE = "CURRENT_TIMESTAMP";
                    dbKeys.UpdateDateTrigger = false;
                    dbKeys.SerialColumn = true;
                    dbKeys.ProviderName = "mysql";
                    dbKeys.ValueGenerationStrategy = "MySQL:AutoIncrement";
                    break;
                case "sqlserver":
                default:
                    dbKeys.DEFAULTDATE_UPDATE = "(getdate())";
                    dbKeys.SerialColumn = SqlServerValueGenerationStrategy.IdentityColumn;
                    dbKeys.ProviderName = "sqlserver";
                    dbKeys.ValueGenerationStrategy = "SqlServer:ValueGenerationStrategy";
                    break;
            }
            if (string.IsNullOrEmpty(dbKeys.DEFAULTDATE_CREATE))
                dbKeys.DEFAULTDATE_CREATE = dbKeys.DEFAULTDATE_UPDATE;
            return dbKeys;
        }
    }
}

Answer 6

太简单了，只需两步：

1.在createDate 字段之上创建具有这些字段的模型：

 [Required, DatabaseGenerated(DatabaseGeneratedOption.Computed)]

2.创建迁移后，在其文件中更新数据库前编辑这部分的列，并添加defaultValueSql: "getdate()"，如下所示：

 id = table.Column<int>(nullable: false)
                    .Annotation("SqlServer:Identity", "1, 1"),
                CreatedDate = table.Column<DateTime>(defaultValueSql: "getdate()",nullable: false)