Backup error, please help

SqlCommand cmd = new SqlCommand();
           cmd.Connection = new SqlConnection(@"Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\dbcn.mdf;Integrated Security=True;Connect Timeout=10;User Instance=True");
           cmd.Connection.Open();
           string dbname = cmd.Connection.Database;//'
           cmd.Connection.Close();
           string pateh="C:\\USERS\\BCMODIR\\DOCUMENTS\\";
           SqlConnection.ClearAllPools();
           string query = "BACKUP DATABASE [" + dbname + "] TO DISK ='"+ pateh+ "\\backup.bak'";
           cmd.Connection = new SqlConnection(@"Data Source=.\sqlexpress;Integrated Security=True;Connect Timeout=30;User Instance=True");
           cmd.Connection.Open();
           cmd.CommandText = query;
           cmd.ExecuteNonQuery();
           cmd.Connection.Close();
           MessageBox.Show("database backup: ok");

Invalid column name 'is_compressed'.
Invalid column name 'compressed_backup_size'.
Could not insert a backup or restore history/detail record in the msdb database. This may indicate a problem with the msdb database. The backup/restore operation was still successful.
Processed 184 pages for database 'C:\USERS\BCMODIR\DOCUMENTS\VISUAL STUDIO 2010\PROJECTS\FRMSABT\FRMSABT\BIN\DEBUG\DBCN.MDF', file 'dbcn' on file 3.
Processed 1 pages for database 'C:\USERS\BCMODIR\DOCUMENTS\VISUAL STUDIO 2010\PROJECTS\FRMSABT\FRMSABT\BIN\DEBUG\DBCN.MDF', file 'dbcn_log' on file 3.
BACKUP DATABASE successfully processed 185 pages in 0.271 seconds (5.333 MB/sec).