Consider adding template methods for DbConnection calls

[ajcvickers]

For #7283 I need to call a different overload of DbConnection.Open in the SQL Server provider. I'm adding a template method to allow this, but similar template methods could be useful in other providers. Tentative list of relevant methods based on what RelationalCommand calls:

• BeginTransaction
• Close
• EnlistTransaction
• State
• Dispose

We could also consider doing this for other Db types where they are wrapped by EF.

[KaloyanIT]

Hi, I'm interested in contributing. In which providers should be added more template methods?

[ajcvickers]

These should be added to RelationalConnection as was done for OpenDbConnection in https://github.com/dotnet/efcore/pull/21328/files

[KaloyanIT]

I am not sure that I understand completely what should be done? Should these template methods be implemented in child classes of RelationalConnection?

[ajcvickers]

@KaloyanIT The PR above added a new method OpenDbConnection like this:

protected virtual void OpenDbConnection(bool errorsExpected)
            => DbConnection.Open();

It simply calls DbConnection.Open(). This is the kind of template method we're talking about here. These methods do not need to be overridden in any providers as part of this change. However, it makes it possible for providers to override these methods. That's what the objective is here.

[joaopgrassi]

@KaloyanIT are you still working on this? If not I could take it. (looking to plant a tree this October 😊). @ajcvickers , I took at look at RelationalConnection where you added the OpenDbConnection but most methods in the list above are already virtual, like BeginTransaction so what is actually needed to change?