告诉EF自动计算并插入创建行的当前日期时间？ [英] Tell EF to automatically compute and insert the current date time when the row is created?

问题描述

当我插入新行时，我想插入当前的日期时间。

我正在使用EF 6，MVC 5的Code First方法

搜索后，我得到了这个

  [DatabaseGenerated（DatabaseGeneratedOption.Computed）] 
 public DateTime？ CreatedDate {get;组; 
  

它必须以模型类编写，但是当插入新记录时，NULL被保存在DB中，我注意到这只是CreatedDate的声明，在哪里编写CreatedDate = DateTime.Now
或任何其他方式来解决它。

我的整个模型

  namespace December.Models 
 {
 [Table（tblLibray）] 
 public class Library 
 {
 [Key] 
 public int Id {get;组; } 
 [必需] 
 public string BookName {get;组; } 
 [必需] 
 public string Author {get;组; } 
 [必需] 
 public string说明{get;组; } 
 [必需] 
公开十进制MRP {get;组; } 
 
 [DatabaseGenerated（DatabaseGeneratedOption.Computed）] 
 public DateTime？ CreatedDate {get;组; 
} 
} 
  

解决方案

[DatabaseGenerated（DatabaseGeneratedOption.Computed）] 属性允许您跳过实体框架验证，但由于您的 DateTime 可空，您不需要它。

创建一个新课程

 内部类AutoDateTimeMigrationSqlGenerator：SqlServerMigrationSqlGenerator //：NpgsqlMigrationSqlGenerator 
 {
 protected override void Generate（AddColumnOperation addColumnOperation）
 {
 SetCreatedDateColumn（addColumnOperation.Column）; 
 
 base.Generate（addColumnOperation）; 
} 
 
 protected override void生成（CreateTableOperation createTableOperation）
 {
 SetCreatedDateColumn（createTableOperation.Columns）; 
 
 base.Generate（createTableOperation）; 
} 
 
 private static void SetCreatedDateColumn（IEnumerable< ColumnModel>列）
 {
 foreach（列中的var columnModel）
 {
 SetCreatedDateColumn （columnModel）; 
} 
} 
 
 private static void SetCreatedDateColumn（PropertyModel column）
 {
 if（column.Name ==CreatedDate）
 {
 column.DefaultValueSql =GETUTCDATE（）; 
} 
} 
} 
  

在您的 Configuration.cs 文件（具有从 DbMigrationsConfiguration 继承的迁移配置类的文件）在类构造函数中添加以下行：

  public Configuration（）
 {
 AutomaticMigrationsEnabled = false; 
 SetSqlGenerator（System.Data.SqlClient，new AutoDateTimeMigrationSqlGenerator（））
} 
  

PS：更新数据库所有这些。

I want to insert current Datetime when ever a new row is inserted.
I am using Code First Approach of EF 6,MVC 5
After searching I got this

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

It has to be written in Models Class,but when ever a new record is inserted NULL is saved in DB,I have noticed that this is just declaration of CreatedDate,where to write CreatedDate = DateTime.Now OR any other way to solve it.
My Entire Model

namespace December.Models
{   
    [Table("tblLibray")]
    public class Library
    {   
        [Key]
        public int Id { get; set; }
        [Required]
        public string BookName { get; set; }
        [Required]
        public  string Author { get; set; }
        [Required]
        public string Description { get; set; }
        [Required]
        public decimal MRP { get; set; }

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

解决方案

The [DatabaseGenerated(DatabaseGeneratedOption.Computed)] attribute allows you to skip entity framework validation, but since your DateTime prop is nullable, you don't need it.

Create a new class

internal class AutoDateTimeMigrationSqlGenerator: SqlServerMigrationSqlGenerator //:NpgsqlMigrationSqlGenerator 
    {
        protected override void Generate(AddColumnOperation addColumnOperation)
        {
            SetCreatedDateColumn(addColumnOperation.Column);

            base.Generate(addColumnOperation);
        }

        protected override void Generate(CreateTableOperation createTableOperation)
        {
            SetCreatedDateColumn(createTableOperation.Columns);

            base.Generate(createTableOperation);
        }

        private static void SetCreatedDateColumn(IEnumerable<ColumnModel> columns)
        {
            foreach (var columnModel in columns)
            {
                SetCreatedDateColumn(columnModel);
            }
        }

        private static void SetCreatedDateColumn(PropertyModel column)
        {
            if (column.Name == "CreatedDate")
            {
                column.DefaultValueSql = "GETUTCDATE()";
            }
        }
    }

In your Configuration.cs file (the one with the migration configuration class that inherits from DbMigrationsConfiguration<>) add the following line in the class constructor:

public Configuration()
{
      AutomaticMigrationsEnabled = false;
      SetSqlGenerator("System.Data.SqlClient", new AutoDateTimeMigrationSqlGenerator())
}

PS: Update-Database after all this.

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