Only open certain file extension and checking if the first two parts of that file are integers

Question

The program I am writing opens a .DAT file with the given format:

10 10
OO+E+OO+++
O++O+O+OOO
OOOOOO+O+O
+++++O++OO
OOO+OOO+O+
O+O+O+++O+
O+O+OOO+OO
++O+++O++O
O+OOOOO++O
O+O++O+OOO

1. How can I block the user from opening any other file extension other than .DAT? For example, if they attempt to open a .PNG file, it will throw the MessageBox below of "Not a proper maze file!"

2. I also want this to happen when the first two parts of the file once opened are not both integers.

   OpenFileDialog ^ fileDialog = gcnew OpenFileDialog();
   fileDialog->InitialDirectory = ".";
   if (fileDialog->ShowDialog() == ::DialogResult::OK)
   {
      wchar_t fileName[1024];
      for (int i = 0; i < fileDialog->FileName->Length; i++)
         fileName[i] = fileDialog->FileName[i];
      fileName[fileDialog->FileName->Length] = '\0';
   
      ifstream ifs;
      ifs.open(fileName);
      maze = new Maze( mazePanel, ifs );
      ifs.close();
      if (maze->IsValid())
      {
         showOriginalBtn->Show();
         mazePanel->Show();
      }
      else
      {
         MessageBox::Show( "Not a proper maze file!" );
         mazePanel->Hide();
      }
   }
   

Here is the code where I am reading in the maze file and storing it into its proper places:

   valid = true;
   free = false;
   ifs >> width >> height;
   if ( width <= MAXSIZE && height <= MAXSIZE)
   {
      panel = drawingPanel;
      panel->Width = width * CELLSIZE;
      panel->Height = height * CELLSIZE;
   }
   else
      valid = false;

   char value;
   for (int i = 0; i < height; i++)
      for (int j = 0; j < width; j++)
      {
         ifs >> value;
         if (value != EXIT && value != DEADEND && value != OPEN)
         {
            valid = false;
            return;
         }
         orig[j][i] = value;
         solved[j][i] = value;
      }

Answer 1

You can use the Filter property of the OpenFileDialog to set the extensions that are displayed. Something like:

fileDialog->Filter = ".dat";

Answer 2

1. look for the last occurence of '.' and the next text will be the extension; compare it to DAT.

2. didn't quite understand what you need, so I will assume you meant you need a check for the first 2 parts. In this case, you can do if (std::cin >> int1 && std::cin >> int2) { /*...*/ }. >> will return false if the format of the input does not match the type of int1 and int2.

--Edit Responding to your comment, here is how you could iterate over a wchar_t[].

    wchar_t t[] = { 'a', 'b', '.', 'D', 'A', 'T' };

    std::wstring s;

    for (int i = 5; t[i] != '.'; i--) {

        s = t[i] + s;

    }

    std::wcout << s << std::endl; //DAT