如何在实体框架迁移中获取当前连接字符串？

Question

Is there any migration property or singleton class the returns the current connection string inside a Entity Framework 5/6 migration? I need this inside of the migration "Up" method, I know it may sounds strange but I need this to perform some specific automation...

Answer 1

The Up method is not connected. it only generates operations that will be executed later by the DbMigrator . If you want to do anything with a connection during a migration your only chance is the Seed method.

Answer 2

Well it does sound a bit 'unortodox' :), but...

I'd suggest to use the Seed method of your Configuration

var connection = context.Database.Connection.ConnectionString;

For migration Up/Down you could do something like this...

This works when you have a 'running' DbContext.

using (var db = new YourDbContext())
{
    var connection = db.Database.Connection.ConnectionString;
}

(I didn't try that - as it should run)

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EDIT: How To Get a Connections Cache w/o DbContext (Entity Framework):

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I think I understand now what you're trying to do (based on comments).

You can get all connections using Reflection and from an internal static dictionary

 IEnumerable<string> EnumerateConnections() { var lazyInternalContextType = typeof(DbContext).Assembly .GetType("System.Data.Entity.Internal.LazyInternalContext"); var propertyDbs = lazyInternalContextType.GetField( "InitializedDatabases", BindingFlags.Static | BindingFlags.NonPublic | BindingFlags.Public); var lazyContext = propertyDbs.GetValue(null); foreach (var pair in (IEnumerable)lazyContext) { var key = pair.GetType().GetProperty("Key")?.GetValue(pair, null); var tuple = (Tuple<System.Data.Entity.Infrastructure.DbCompiledModel, string>)key; yield return tuple.Item2; // need to replace "System.Data.SqlClient.SqlConnection;" with "" in EF6. } } var connectionName = EnumerateConnections().Distinct().SingleOrDefault();

You can put that into Up/Down - and you should get one 'distinct' connection that was used.

This works providing you do not mix different connections. In that case you'd need to tweak this based on your scenario.

(should work for both EF5 and EF6, classes are the same - I just confirmed it fast for EF5):

Enjoy :)