How to store database name in entity class

Question

I want to create a read-only property [NotMapped]Database {get;} on a POCO entity class to reflect the name of the database from which the entity was loaded at the time of creation so that I can read the value later when no DbContext instance is available. How do I tell EF to load this data at object creation time?

I know about context.Database.Connection.ConnectionString, but that is not what I want to do. I want to set the property to the current database name when the object is being instantiated via a DbContext class.

I have searched for this problem but haven't been able to find any information to provide here, perhaps I don't know how to phrase the question.

Evk · Accepted Answer · 2016-11-08 20:32:31Z

2

You can do it like this. First create some interface:

public interface IHasDatabaseName {
    string Database { set; }
}

And implement for entity in question. Then in constructor of your DbContext (or at any place where you construct your DbContext, if you use DI container for example), subscribe to ObjectMaterialized event:

// this is DbContext here
((IObjectContextAdapter) this).ObjectContext.ObjectMaterialized += ObjectContextOnObjectMaterialized;

And then:

// this is DbContext here
private void ObjectContextOnObjectMaterialized(object sender, ObjectMaterializedEventArgs objectMaterializedEventArgs) {
    var dbName = objectMaterializedEventArgs.Entity as IHasDatabaseName;
    if (dbName != null) {
        dbName.Database = this.Database.Connection.Database;
    }
}

answered Nov 8, 2016 at 20:32

Evk

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Comments

Wagner DosAnjos · Accepted Answer · 2016-11-08 20:22:11Z

0

I think you need to create a computed column on the table to fetch that information. Something like:

alter table YourTable add [Database] AS DB_NAME();

Then define your POCO property as Database {get;}.

answered Nov 8, 2016 at 20:22

Wagner DosAnjos

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1 Comment

Keith Over a year ago

I can't modify the storage layer and because I want this value on every class, that would be too large an undertaking.

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