You should delete old child items thisParent.ChildItems one by one manually. Entity Framework doesn’t do that for you. It finally cannot decide what you want to do with the old child items – if you want to throw them away or if you want to keep and assign them to other parent entities. You must … Read more
There is a lot to say about this. Let me focus on AsEnumerable and AsQueryable and mention ToList() along the way. What do these methods do? AsEnumerable and AsQueryable cast or convert to IEnumerable or IQueryable, respectively. I say cast or convert with a reason: When the source object already implements the target interface, the … Read more
Try this: var sql = @”Update [User] SET FirstName = @FirstName WHERE Id = @Id”; ctx.Database.ExecuteSqlCommand( sql, new SqlParameter(“@FirstName”, firstname), new SqlParameter(“@Id”, id));
You can do it by manually edit code first migration: public override void Up() { AddColumn(“dbo.Events”, “Active”, c => c.Boolean(nullable: false, defaultValue: true)); }
You can have multiple contexts for single database. It can be useful for example if your database contains multiple database schemas and you want to handle each of them as separate self contained area. The problem is when you want to use code first to create your database – only single context in your application … Read more
With Entity Framework 6.1, you can now do this: [Index(“IX_FirstAndSecond”, 1, IsUnique = true)] public int FirstColumn { get; set; } [Index(“IX_FirstAndSecond”, 2, IsUnique = true)] public int SecondColumn { get; set; } The second parameter in the attribute is where you can specify the order of the columns in the index. More information: MSDN
You need to : Delete the state: Delete the migrations folder in your project; And Delete the __MigrationHistory table in your database (may be under system tables); Then Run the following command in the Package Manager Console: Enable-Migrations -EnableAutomaticMigrations -Force Use with or without -EnableAutomaticMigrations And finally, you can run: Add-Migration Initial
I ran into this and it was caused by the entity’s ID (key) field not being set. Thus when the context went to save the data, it could not find an ID = 0. Be sure to place a break point in your update statement and verify that the entity’s ID has been set. From … Read more
EntityFramework 6 has made this a bit easier with .RemoveRange(). Example: db.People.RemoveRange(db.People.Where(x => x.State == “CA”)); db.SaveChanges(); Warning! Do not use this on large datasets! EF pulls all the data into memory, THEN deletes it. For smaller data sets this might not be an issue but generally avoid this style of delete unless you can … Read more
I want to add some clarification to this thread: Update-Database -TargetMigration:”name_of_migration” What you are doing above is saying that you want to rollback all migrations UNTIL you’re left with the migration specified. Thus, if you use GET-MIGRATIONS and you find that you have A, B, C, D, and E, then using this command will rollback … Read more