What program lock the file - delphi

Question

I need a program to overwrite the file, but sometimes some process is lock it. How to check which process locks a file, and how to unlock it? What functions should I use?
I found on the Internet such a code, but it doesn't work me.
unit proc;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, ExtCtrls, StdCtrls, ComCtrls, Grids, ValEdit, MTSUtilsUnit, TLHelp32,
Menus, PsAPI;
type
TApp = class
fPID: Integer;
fPArentPID: Integer;
fPIDName: string;
fThread: Integer;
fDLLName: TStringList;
fDLLPath: TStringList;
fDescription: string;
end;
TForm2 = class(TForm)
StatusBar1: TStatusBar;
Panel1: TPanel;
Panel2: TPanel;
Panel3: TPanel;
Panel4: TPanel;
Splitter2: TSplitter;
Edit1: TEdit;
Button1: TButton;
Label1: TLabel;
RichEdit1: TRichEdit;
PopupMenu1: TPopupMenu;
kill1: TMenuItem;
StringGrid1: TStringGrid;
function GetApps(AppName: string): TStringList;
function GetInfo(PID: Integer): string;
function Kill(PID: Integer): Boolean;
procedure kill1Click(Sender: TObject);
procedure Button1Click(Sender: TObject);
procedure FormCreate(Sender: TObject);
procedure StringGrid1SelectCell(Sender: TObject; ACol, ARow: Integer;
var CanSelect: Boolean);
private
{ Private declarations }
public
{ Public declarations }
end;
var
Form2: TForm2;
ApplicationList: TStringList;
row: Integer;
implementation
{$R *.dfm}
function TForm2.Kill(PID: Integer): Boolean;
var fHandle: THandle;
begin
fHandle := OpenProcess(PROCESS_TERMINATE, BOOL(0), PID);
if TerminateProcess(fHandle, 0) then
Result := True
else
Result := False;
CloseHandle(fHandle);
end;
procedure TForm2.kill1Click(Sender: TObject);
var i: Integer;
fApp: TApp;
begin
if Kill(StrToInt(StringGrid1.Cells[1, row])) then
begin
ApplicationList.Delete(row);
StringGrid1.RowCount := ApplicationList.Count;
for i := 1 to ApplicationList.Count - 1 do
begin
fApp := TApp(ApplicationList.Objects[i]);
Form2.StringGrid1.Cells[0,i] := fApp.fPIDName;
Form2.StringGrid1.Cells[1,i] := IntToStr(fApp.fPID);
end;
MessageBox(0, 'Terminate successfully', 'Kill', MB_ICONINFORMATION or MB_OK);
end
else
MessageBox(0, 'Could not terminate process', 'Kill', MB_ICONINFORMATION or MB_OK);
end;
procedure TForm2.StringGrid1SelectCell(Sender: TObject; ACol, ARow: Integer;
var CanSelect: Boolean);
var fApp: TApp;
begin
row := ARow;
RichEdit1.Lines.Clear();
if ApplicationList.Count >= row then
begin
fApp := TApp(ApplicationList.Objects[row]);
RichEdit1.Lines.Add(fApp.fDescription);
end;
end;
procedure TForm2.Button1Click(Sender: TObject);
var i: Integer;
fApp: TApp;
sItem: string;
CanSelect: Boolean;
begin
for i := 0 to ApplicationList.Count - 1 do
begin
fApp := TApp(ApplicationList.Objects[i]);
FreeAndNil(fApp.fDLLName);
FreeAndNil(fApp.fDLLPath);
FreeAndNil(fApp);
end;
FreeAndNil(ApplicationList);
ApplicationList := GetApps(Edit1.Text);
StringGrid1.RowCount := ApplicationList.Count;
for i := 0 to ApplicationList.Count - 1 do
begin
fApp := TApp(ApplicationList.Objects[i]);
StringGrid1.Cells[0,i] := fApp.fPIDName;
StringGrid1.Cells[1,i] := IntToStr(fApp.fPID);
end;
StringGrid1.OnSelectCell(Self, 0, 1, CanSelect);
end;
procedure TForm2.FormCreate(Sender: TObject);
begin
StringGrid1.Cells[0,0] := 'Name';
StringGrid1.Cells[1,0] := 'PID';
end;
function TForm2.GetInfo(PID: Integer): string;
var fHandle: THandle;
fModule: TModuleEntry32;
sInfo: string;
begin
Result := '';
sInfo := 'DLL Name: %s'#13#10 +
'DLL Path: %s'#13#10 +
'ModuleId: %d'#13#10;
fHandle := CreateToolhelp32Snapshot(TH32CS_SNAPMODULE, PID);
if fHandle <> INVALID_HANDLE_VALUE then
if Module32First(fHandle, fModule) then
repeat
if SameText(ExtractFileExt(fModule.szModule), '.dll') then
begin
sInfo := Format(sInfo, [fModule.szModule, fModule.szExePath, fModule.th32ModuleID]);
Result := Result + sInfo;
end;
until not Module32Next(fHandle, fModule);
end;
function TForm2.GetApps(AppName: string): TStringList;
var fHandle: THandle;
fModHandle: THandle;
fProcess: TProcessEntry32;
fModule: TMODULEENTRY32;
App: TApp;
i: Integer;
IsDLL: Boolean;
IsProcess: Boolean;
fDesc: string;
sPath: string;
begin
IsDLL := False;
IsProcess := False;
Result := TStringList.Create();
Result.Clear();
fDesc := 'DLL Name: %s'#13#10 +
'DLL Path: %s'#13#10 +
'ModuleId: %d'#13#10;
fHandle := CreateToolHelp32SnapShot(TH32CS_SNAPPROCESS, 0);
fProcess.dwSize := SizeOf(fProcess);
IsProcess := Process32First(fHandle, fProcess);
while IsProcess do
begin
App := TApp.Create();
App.fDLLName := TStringList.Create();
App.fDLLPath := TStringList.Create();
fModHandle := CreateToolHelp32SnapShot(TH32CS_SNAPMODULE, fProcess.th32ProcessID);
IsDLL := Module32First(fModHandle, fModule);
while IsDLL do
begin
if Edit1.Text <> '' then
sPath := fModule.szModule
else
sPath := ExtractFileExt(fModule.szModule);
if SameText(sPath, Edit1.Text + '.dll') then
begin
App.fPID := fProcess.th32ProcessID;
App.fPIDName := fProcess.szExeFile;
App.fDLLName.Add(fModule.szModule);
App.fDLLPath.Add(fModule.szExePath);
App.fDescription := App.fDescription +
Format(fDesc, [fModule.szModule, fModule.szExePath, fModule.th32ModuleID]);
end;
IsDLL := Module32Next(fModHandle, fModule)
end;
if App.fDLLName.Count > 0 then
Result.AddObject(IntToStr(App.fPID), App);
IsProcess := Process32Next(fHandle, fProcess);
end;
CloseHandle(fHandle);
Result.Count;
end;
end.

Answer 1

You should not unlock the file yourself this will lead to lost data! Leave it to the user and instead show an error and explaining which process holds open the file.
This solution here will help you to do so:
http://www.remkoweijnen.nl/blog/2011/01/03/cannot-access-files-but-need-the-origin

Answer 2

Check out Process Explorer. It will show you which processes have which files opened, and will allow you to close individual files.