Querying Data in a System-Versioned Temporal Table in Entity Framework Core
it could be done by an extension method, I found piece of code that may help you :
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Infrastructure;
using Microsoft.EntityFrameworkCore.Internal;
using Microsoft.EntityFrameworkCore.Migrations;
using System;
using System.Linq;
namespace core
{
public static class Extensions
{
public static void AddTemporalTableSupport(this MigrationBuilder builder, string tableName, string historyTableSchema)
{
builder.Sql($@"ALTER TABLE {tableName} ADD
SysStartTime datetime2(0) GENERATED ALWAYS AS ROW START HIDDEN NOT NULL,
SysEndTime datetime2(0) GENERATED ALWAYS AS ROW END HIDDEN NOT NULL,
PERIOD FOR SYSTEM_TIME (SysStartTime, SysEndTime);");
builder.Sql($@"ALTER TABLE {tableName} SET (SYSTEM_VERSIONING = ON (HISTORY_TABLE = {historyTableSchema}.{tableName} ));");
}
public static DbContext GetDbContext<T>(this DbSet<T> dbSet) where T : class
{
var infrastructure = dbSet as IInfrastructure<IServiceProvider>;
return (infrastructure.Instance.GetService(typeof(ICurrentDbContext)) as ICurrentDbContext).Context;
}
public static string GetTableName<T>(this DbSet<T> dbSet) where T : class
{
var entityType = dbSet.GetDbContext().Model.GetEntityTypes().FirstOrDefault(t => t.ClrType == typeof(T))
?? throw new ApplicationException($"Entity type {typeof(T).Name} not found in current database context!");
var tableNameAnnotation = entityType.GetAnnotation("Relational:TableName");
return tableNameAnnotation.Value.ToString();
}
public static IQueryable<T> ForSysTime<T>(this DbSet<T> dbSet, DateTime time) where T : class
{
return dbSet.FromSql($"SELECT * FROM dbo.[{dbSet.GetTableName()}] FOR SYSTEM_TIME AS OF {{0}}", time.ToUniversalTime());
}
}
}
Usage :
var date = DateTime.Parse("2018-08-28 16:30:00");
var students = ctx.student.ForSysTime(date);
this extension method was written by Mirek , you can find the complete article here.
The latest version of Entity Framework Core (6) supports temporal tables.
As mentioned in here Microsoft devBlogs, EF Core 6.0 supports:
- The creation of temporal tables using EF Core migrations
- Transformation of existing tables into temporal tables, again using migrations
- Restoring data from some point in the past
- Querying historical data
Querying historical data can be seen here