Object was open - sql-server

Question

I'm trying to restore a SQL Server database with Delphi. The code that I have is placed in a thread and works - meaning I manage to make the restore. The problem is that I get an error from Delphi saying that "Object is open" and the program stops, even though the restore happens successfully. Why am I getting this problem and how can I fix it? Here's the code:
This is the restore thread:
type
TThreadRestoreBackUp = class( TThread )
protected
procedure Execute(); override;
public
DataSource : TMSDataSource;
Connection : TMSConnection;
Query : TMSQuery;
var
DBName, RestorePath, dbRPath, dbRLogPath : string;
differentDB : Boolean;
end;
This is how I call the thread:
procedure TfrmCreateBackUp.btnRestoreClick(Sender: TObject);
var
RestoreBackUp : BackUpThread.TThreadRestoreBackUp;
begin
RestoreBackUp := BackUpThread.TThreadRestoreBackUp.Create(True);
RestoreBackUp.FreeOnTerminate := True;
try
RestoreBackUp.DataSource := frmMain.MSDSChanges;
RestoreBackUp.Connection := frmMain.MSConnLyubenAirport;
RestoreBackUp.Query := frmMain.MSQChanges;
RestoreBackUp.DBName := edtDBName.Text;
RestoreBackUp.DifferentDB := tcxCheckBoxNewDB.Checked;
RestoreBackUp.RestorePath := cxbeChoosePath.Text;
RestoreBackUp.Start;
except on EConvertError do
RestoreBackUp.Free;
end;
end;
And this is the Execute function of the thread, aka the code that gets run, when I call the thread:
procedure TThreadRestoreBackUp.Execute();
begin
dbRPath := 'E:\ClientDBS\';
dbRLogPath := 'E:\ClientDBS\';
Query.Connection := Connection;
DataSource.DataSet := Query;
if DifferentDB then
begin
dbRPath := dbRPath + DBName + '.mdf';
dbRLogPath := dbRLogPath + DBName + '.ldf';
Query.SQL.Text := 'USE master If DB_ID(' + QuotedStr(DBName) + ') IS NOT NULL BEGIN' +
' ALTER DATABASE [' + DBName + '] SET OFFLINE WITH ROLLBACK IMMEDIATE RESTORE DATABASE [' +
DBName + '] FROM DISK = ' +
QuotedStr(RestorePath) +
' WITH REPLACE, RECOVERY ALTER DATABASE [' + DBName +
'] SET ONLINE END ELSE BEGIN RESTORE DATABASE [' + DBName + ']' +
' FROM DISK = ' + QuotedStr(RestorePath)
+ ' WITH RECOVERY, MOVE ' + QuotedStr('Test') + ' TO ' +
QuotedStr(dbRPath) + ', MOVE ' + QuotedStr('Test_log') +
' TO ' + QuotedStr(dbRLogPath) + 'END';
Query.Execute;
end
else
begin
DBName := Connection.Database;
Query.SQL.Text := 'USE master ALTER DATABASE [' + DBName +
'] SET OFFLINE WITH ROLLBACK IMMEDIATE' +
' RESTORE DATABASE [' + DBName +
'] FROM DISK = ' + QuotedStr(RestorePath) +
' WITH REPLACE, RECOVERY ALTER DATABASE [' + DBName +
'] SET ONLINE';
Query.Execute;
end;
DataSource.Free;
Connection.Free;
Query.Free;
end;
Here's an explanation on how it works: I have a form in which I can choose a path from a tcxButtonEdit, which opens TOpenDialog when the button is pressed. When the path is chosen I have option to press a checkbox, which indicates whether the user wants to restore in the database used, or in a different one. Then the user can enter the name of the different database or the new database if they want to save in another database and not the original. When the button Restore is pressed the thread is called and executed. The code inside the thread sets up the things needed for the restore, like paths for the files, connection, tmsQuery and DataSource. Then if it's the checkbox is checked then the if statement receives true, and makes the restore in the different database, if not then it does it in the same.