CODEWITHSUNDEEP
c#entity-framework
MyDaftQuestions
MyDaftQuestions

Reputation: 4701

How to use EF to copy and paste tables between 2 databases

I have 2 databases - one for live, the other for production

I need to replicate an issue on live, and so I thought the best thing is to copy the tables from my live database to my local database!

This means copying several tables (relational in my SQLExpress database) to my local SQL Server Compact db.

I am unable to do this because I get the following exception

An entity object cannot be referenced by multiple instances of IEntityChangeTracker.

My effort is

var dc = new DalCf.StagePlanEntities(Bll.ProgramState.LIVE-ConnectionString); //query LIVE
var account = dc.Accounts.Single(a => a.EmailAddress.Contains(emailaddress));
dc = null; //does not remove the tracking 
var localDc = new DalCf.StagePlanEntities(Bll.ProgramState.LOCAL-ConnectionString);//now LOCAL
localDc.Accounts.Add(account);
localDc.SaveChanges();

Is this even the best way to duplicate the tables?

Upvotes: 0

Views: 49

Answers (1)

Jens Stragier
Jens Stragier

Reputation: 223

The dc.Accounts.Single() produces a tracked entity. You can add ".AsNoTracking()" to the query to disable this feature (for that particular query).

    var account = dc.Accounts.AsNoTracking().Single(a => a.EmailAddress.Contains(emailaddress));

https://learn.microsoft.com/en-us/ef/core/querying/tracking

By default, queries that return entity types are tracking. Which means you can make changes to those entity instances and have those changes persisted by SaveChanges(). In the following example, the change to the blogs rating will be detected and persisted to the database during SaveChanges().

Upvotes: 1

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