DbCommand and connection - why does dispose not close underlying connection?

Question

I've seen this in some legacy code which generates code analysis warnings:

  Database db = DatabaseFactory.CreateDatabase(strDBCon);
  DbCommand dbCommand = db.GetSqlStringCommand(sb.ToString());

  using (IDataReader dataReader = db.ExecuteReader(dbCommand))
  {
     while (dataReader.Read())
     {
     }
     dataReader.Close();  // <-- this is redundant as close is covered by using's implicit dispose
  }
  dbCommand.Connection.Close();
  dbCommand.Dispose();
  db = null;

I've read here on SO that the dbCommand.Connection property must be closed in addition to disposing of the dbCommand. I would have thought that dbCommand would dispose of any child disposable objects, in this case Connection. If this is not the case, why?

What if you wanted to use the same connection for several commands? Generally if you're passing in a disposable object to another disposable object you're responsible for the one you're passing in. — George Duckett
– George Duckett, Commented May 1, 2013 at 10:14
Ok, but it doesn't seem clear from the code that the command object holds a reference to an already created connection rather than one it itself has created. In this case if the db and dbCommand variable are wrapped in using, I'm guessing the db dispose would close the connection? — jaffa
– jaffa, Commented May 1, 2013 at 10:23
I'm assuming strDBCon is a string, so that means the Database object is creating the connection object, which to me implies that it is Disposable and when disposed it would dispose the connection that it created. — George Duckett
– George Duckett, Commented May 1, 2013 at 10:26

Grant Thomas · Accepted Answer · 2013-05-01 10:16:42Z

3

Types have a choice in this respect to either take ownership of a thing or just utilise a thing. In your case, and this specifically, all you're doing is passing in an existing instance that you've created and could well be expecting to use again.

If the type was explicitly constructed with an instance of a type passed in, you might expect it to take ownership of that instance, and therefore manage it as part of its disposal pattern, but not in the case of a transient method call.

answered May 1, 2013 at 10:16

Grant Thomas

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1 Comment

jaffa Over a year ago

ok I understand thanks. Please see my last edit above to George.

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