如何使用C＃以数据库优先方式拥有审核列？

Question

I need to add audit columns (created by, created on, modified by and modified on) for all the tables in my MVC project (web-application). I thought of having a base class with these 4 columns and inheriting all the other classes. But I am using Database-First approach, hence EF has generated all the classes. I am not sure how can I add the audit columns and the base class inheritance.

Answer 1

I assume that it is not possible to perform your desired operation via EF Database first. But in order to add specific fields to all tables of a database you can use the following code for each field in Sql Server and then update your EF model.

DECLARE @TableName VARCHAR(100)
DECLARE @TableSchema VARCHAR(100)
DECLARE @COLUMN_NAME VARCHAR(50)
SET @COLUMN_NAME='CreatedOn' 
DECLARE @COLUMN_DATATYPE VARCHAR(50)
SET @COLUMN_DATATYPE='DateTime'

DECLARE CUR CURSOR FOR
  SELECT TABLE_SCHEMA,
         TABLE_NAME
  FROM   INFORMATION_SCHEMA.TABLES
  WHERE  TABLE_TYPE = 'BASE TABLE'
OPEN CUR
FETCH NEXT FROM CUR INTO @TableSchema,@TableName
WHILE @@FETCH_STATUS = 0
  BEGIN

  DECLARE @SQL NVARCHAR(MAX)
  SET @SQL=NULL
  IF NOT EXISTS ( SELECT 1 FROM INFORMATION_SCHEMA.COLUMNS 
       WHERE TABLE_NAME=@TableName AND COLUMN_NAME = @COLUMN_NAME  and Table_Schema=@TableSchema)
  BEGIN
  SET @SQL='ALTER TABLE '+ @TableSchema+'.'+ @TableName +' ADD '+ @COLUMN_NAME + ' '+ @COLUMN_DATATYPE
    PRINT @SQL
    EXEC(@SQL)
  END

  IF EXISTS ( SELECT 1 FROM INFORMATION_SCHEMA.COLUMNS 
              WHERE TABLE_NAME=@TableName AND COLUMN_NAME=@COLUMN_NAME and Table_Schema=@TableSchema)
  BEGIN
    PRINT 'Column Already exists in Table'
  END
      FETCH NEXT FROM CUR INTO @TableSchema,@TableName
  END
CLOSE CUR
DEALLOCATE CUR

Answer 2

Database first means you have to add all the fields to the database manually and AFAIK there is no inheritance. You could write a SQL script adding those columns. As Mahyar said. But you would still lack the inheritance.

Or you switch to code first. Then you can define an interface and handle auditing in code. As shown here . I, for example, use this interface:

    /// <summary>
    /// Adds auditing properties to an entity.
    /// </summary>
    public interface IAuditedEntity
    {
        /// <summary>
        /// Date and time of the entity's creation. Usually in UTC.
        /// </summary>
        /// <remarks>Best set via a <see cref="ITimeProvider"/>.</remarks>
        DateTime DateCreated { get; set; }

        /// <summary>
        /// Identification who created this instance.
        /// </summary>
        /// <remarks>Best set via a <see cref="ICurrentUserIdProvider"/>.</remarks>
        string CreatedBy { get; set; }

        /// <summary>
        /// Date and time of last modification. Usually in UTC.
        /// </summary>
        /// <remarks>Best set via a <see cref="ITimeProvider"/>.</remarks>
        DateTime? DateModified { get; set; }

        /// <summary>
        /// Last one modifiying this instance.
        /// </summary>
        /// <remarks>Best set via a <see cref="ICurrentUserIdProvider"/>.</remarks>
       string ModifiedBy { get; set; }
}

The user provider interface is defined like this:

    /// <summary>
    /// Interface for providing the current user's id.
    /// </summary>
    public interface ICurrentUserIdProvider
    {
        /// <summary>
        /// Get the id of the curent user.
        /// </summary>
        /// <returns></returns>
        string GetCurrentUserId();
    }

For testing purposes you now can use an ambient context/service delivering the current user or any user you need to test your logic.