Invalid attempt to call FieldCount when reader is closed

The error above occurs when I try to do a dataReader.Read on the data recieved from the database. I know there are two rows in there so it isnt because no data actually exists.

Could it be the CommandBehavior.CloseConnection, causing the problem? I was told you had to do this right after a ExecuteReader? Is this correct?

        try
        {
            _connection.Open();
            using (_connection)
            {
                SqlCommand command = new SqlCommand("SELECT * FROM Structure", _connection);
                SqlDataReader dataReader = command.ExecuteReader(CommandBehavior.CloseConnection);

                if (dataReader == null) return null;

                var newData = new List<Structure>();
                while (dataReader.Read())
                {
                    var entity = new Structure
                    {
                        Id = (int)dataReader["StructureID"],
                        Path = (string)dataReader["Path"],
                        PathLevel = (string)dataReader["PathLevel"],
                        Description = (string)dataReader["Description"]
                    };

                    newData.Add(entity);
                }
                dataReader.Close();

                return newData;
            }
        }
        catch (SqlException ex)
        {
            AddError(new ErrorModel("An SqlException error has occured whilst trying to return descendants", ErrorHelper.ErrorTypes.Critical, ex));
            return null;
        }
        catch (Exception ex)
        {
            AddError(new ErrorModel("An error has occured whilst trying to return descendants", ErrorHelper.ErrorTypes.Critical, ex));
            return null;
        }
        finally
        {
            _connection.Close();
        }
    }

Thanks in advance for any help.

Clare

Solution

Your code, as displayed is fine. I've taken it into a test project, and it works. It's not immediately clear why you get this message with the code shown above. Here are some debugging tips/suggestions. I hope they're valuable for you.

Create a breakpoint on the while (dataReader.Read()). Before it enters its codeblock, enter this in your Immediate or Watch Window: dataReader.HasRows. That should evaluate to true.
While stopped on that Read(), open your Locals window to inspect all the properties of dataReader. Ensure that the FieldCount is what you expect from your SELECT statement.
When stepping into this Read() iteration, does a student object get created at all? What's the value of dataReader["StructureID"] and all others in the Immediate Window?

It's not the CommandBehavior.CloseConnection causing the problem. That simply tells the connection to also close itself when you close the datareader.