Will putting a "using" statement around a DataReader close it?

Question

I usually write my DataReader code like this:

try {     dr = cmd.ExecuteReader(CommandBehavior.SingleResult);     while (dr.Read())     {         // Do stuff     } } finally {     if (dr != null) { dr.Close(); } } 

Is it safe to replace the try and finally with just a using block around the DataReader's creation? The reason I wonder is because in all the Microsoft examples I've seen they use a using for the connection but always explicitly call Close() on the DataReader.

Heres's an example from Retrieving Data Using a DataReader (ADO.NET):

static void HasRows(SqlConnection connection) {     using (connection)     {         SqlCommand command = new SqlCommand(           "SELECT CategoryID, CategoryName FROM Categories;",           connection);         connection.Open();          SqlDataReader reader = command.ExecuteReader();          if (reader.HasRows)         {             while (reader.Read())             {                 Console.WriteLine("{0}\t{1}", reader.GetInt32(0),                     reader.GetString(1));             }         }         else         {             Console.WriteLine("No rows found.");         }         reader.Close();     } } 

Answer 1

Yes. using calls Dispose. Calling Dispose on SqlDataReader closes it.

This is psuedo-code of SqlDataReader gleaned from Reflector:

    public void Dispose()     {         this.Close();     }      public override void Close()     {         if( !IsClosed )             CloseInternal(true);     }      private void CloseInternal(bool closeReader)     {         try         {             // Do some stuff to close the reader itself         }         catch(Exception ex)         {             this.Connection.Abort();             throw;         }          if( this.Connection != null && CommandBehavior.CloseConnection == true )         {             this.Connection.Close();         }     }