error in creating backup DB: Invalid column name "is_compressed"...

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C#

SQL

IS THIS QUESTION NOT CLEAR??!!

for backup Db in sqlExpress 2008 i use code:

strFileName = "BackupFile.bak";
try 
{     
    this.Cursor = Cursors.WaitCursor;     
    SqlCommand cmd = new SqlCommand();     
    SqlConnection.ClearAllPools();     
    cmd.Connection = new SqlConnection("Data Source=.\\SQLEXPRESS;AttachDbFilename=|DataDirecto  ry|\\file.mdf;Integrated Security=True;Connect Timeout=30;User Instance=True");     
    
    cmd.Connection.Open();     
    string dbname = cmd.Connection.Database;     
    cmd.Connection.Close();     
    string query = "BACKUP DATABASE [" + dbname + "] TO DISK ='" + Masir.ToString().Trim() + "\\" + strFileName + "'";     
    cmd.Connection = new SqlConnection("Data Source=.\\SQLEXPRESS;AttachDbFilename=|DataDirecto ry|\\file.mdf;Integrated Security=True;Connect Timeout=30;User Instance=True;");     
    
    cmd.Connection.Open();     
    cmd.CommandText = query;     
    cmd.ExecuteNonQuery();     
    cmd.Connection.Close();     
    this.Cursor = Cursors.Default;
    MessageBox.Show("backup successful", "backup", MessageBoxButtons.OK, MessageBoxIcon.Information); 
}
catch (Exception ex) 
{     
    MessageBox.Show("Error Occurd : " + ex.Message); 
}
//end code

Here is Error:

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.

please help.thanks