MySQL Bugs: #58652: ExecuteReader throws NullReferenceException when using CommandBehavior.Close

Bug #58652	ExecuteReader throws NullReferenceException when using CommandBehavior.Close
Submitted:	2 Dec 2010 10:32	Modified:	7 Jan 2011 15:39
Reporter:	Jaco Erasmus	Email Updates:
Status:	Closed	Impact on me:	None
Category:	Connector / NET	Severity:	S2 (Serious)
Version:	6.3.5	OS:	Windows
Assigned to:	Reggie Burnett	CPU Architecture:	Any
Tags:	CommandBehavior, ExecuteReader, MySqlCommand, NullReferenceException

Description:
MySqlCommand.ExecuteReader(CommandBehavior) throws a NullReferenceException when being called with CommandBehavior.CloseConnection if the SQL statement has an error or is invalid, e.g. Invalid column name.

Instead it should throw a MySqlException with the correct underlying error message (e.g. Unknown column 'InvalidColumn' in 'field list'), as is the case when calling MySqlCommand.ExecuteReader().

StackTrace:
===========
at MySql.Data.MySqlClient.MySqlConnection.get_ServerThread()
at MySql.Data.MySqlClient.MySqlConnection.Abort()
at MySql.Data.MySqlClient.MySqlCommand.ExecuteReader(CommandBehavior behavior) 
at BugTests.ObjectReferenceTests.ExecuteReader_InvalidColumnName()

How to repeat:
1.) Create test table: CREATE TABLE Test (Id int NOT NULL, Name VARCHAR(100))
2.) Execute select statement with invalid column name (as in code below)
3.) Expect MySqlException with message "Unknown column 'InvalidColumn' in 'field list'", instead receives NullReferenceException

try
{
  string connStr = "CONNECTION STRING HERE";
  using (MySqlConnection conn = new MySqlConnection(connStr))
  {
    conn.Open();

    // Select invalid column
    string sql = "SELECT Id, Name, InvalidColumn FROM Test";
    using (MySqlCommand cmd = new MySqlCommand(sql, conn))
    {
      using (MySqlDataReader reader = cmd.ExecuteReader(CommandBehavior.CloseConnection))
      {
        Assert.AreEqual(0, reader.RecordsAffected);
      }
    }
  }
}
catch (Exception ex)
{
  throw ex;
}

Hi Jaco and thanks for your report.

Verified just as described with following test case:
    string s = "Server=opensol;Database=mysql;Uid=**;pwd=**;logging=true";
            using (MySqlConnection conn = new MySqlConnection(s))
            {
                conn.Open();

                // Select invalid column
                string sql = "SELECT User, Host, Pswrd FROM user";
                using (MySqlCommand cmd = new MySqlCommand(sql, conn))
                {
                    using (MySqlDataReader reader =
                        cmd.ExecuteReader(CommandBehavior.CloseConnection))
                    {
                        Assert.AreEqual(0, reader.RecordsAffected);
                    }
                }
            }

Problem is in command.cs, right about line 469 where this case is not handled and later on original exception gets overwritten with new one.

Fixed in 6.0.8, 6.1.6, 6.2.5, 6.3.6+

An entry has been added to the 6.0.8, 6.1.6, 6.2.5, 6.3.6 changelogs:

MySqlCommand.ExecuteReader(CommandBehavior) threw a NullReferenceException when being called with CommandBehavior.CloseConnection, if the SQL statement contained a syntax error, or contained invalid data such as an invalid column name.