怎么获取一个文件的大小

//获取文件的大小，单位为字节
function GetFileSize(const FileName: string): integer;
  function ReadFromTextFile(const FileName: string): string;
  var
    Size: integer;
    Stream: TStream;
  begin
    Result := '';
    if not FileExists(FileName) then Exit;

    Stream := TFileStream.Create(FileName, fmOpenRead or fmShareDenyWrite);
    try
      Size := Stream.Size - Stream.Position;
      SetString(Result, nil, Size);
      Stream.Read(Pointer(Result)^, Size);
    finally
      Stream.Free;
    end;
  end;
var
  sTemp: string;
begin
  Result := 0;
  if not FileExists(FileName) then Exit;

  sTemp := ReadFromTextFile(FileName);
  Result := Length(sTemp);
end;

------解决方案--------------------

Delphi(Pascal) code

var
  F: file of Byte;
　nSize: Longint;
begin
  AssignFile(F, 'C:\MyFile.txt'); 
　Reset(F); 
  nSize := FileSize(F); 
  CloseFile(F); 
end;

------解决方案--------------------

Delphi(Pascal) code

FFile_Handle:THandle;  
//FSourceFileName是文件名

FFile_Handle := CreateFile(PChar(FSourceFileName),GENERIC_READ,FILE_SHARE_READ,nil,OPEN_EXISTING,FILE_ATTRIBUTE_NORMAL,0);  
  if FFile_Handle = INVALID_HANDLE_VALUE then Exit;  
  //获取文件尺寸   
  filesize := GetFileSize(FFile_Handle,nil);