What's the best way to handle text file operations in a Windows GUI app?

Other Questions API
1

I’m working on a Windows GUI app and I need some help with file operations. I’ve set up an open file dialog using OPENFILENAME, but I’m stuck on how to actually read the file contents and display them in a text box.

Here’s what I’ve got so far:

void ShowFileContents()
{
    OPENFILENAME ofn;
    HWND mainWindow = NULL;
    HANDLE fileHandle;

    ZeroMemory(&ofn, sizeof(ofn));
    ofn.lStructSize = sizeof(ofn);
    ofn.hwndOwner = mainWindow;
    ofn.nMaxFile = MAX_PATH;
    ofn.lpstrFilter = L"Text Files\0*.txt\0All Files\0*.*\0";
    ofn.nFilterIndex = 1;
    ofn.Flags = OFN_PATHMUSTEXIST | OFN_FILEMUSTEXIST;

    if (GetOpenFileName(&ofn))
    {
        fileHandle = CreateFile(ofn.lpstrFile, GENERIC_READ, 0, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
        // What next?
    }
}

I’m calling this function when the user clicks a button, but I’m not sure how to read the file and put its contents in my text box control.

Also, I’d like to add a save feature. Any tips on implementing a save file dialog and writing to files?

I’m new to C++ and the Windows API, so any help or explanations would be great. Thanks!

2

I’ve been down this road before, and I can tell you it’s tricky at first. For reading the file, after CreateFile(), you’ll want to use ReadFile(). But here’s a gotcha - make sure you allocate enough memory for your buffer. I once spent hours debugging because I underestimated file size!

For displaying in the text box, SetWindowText() is your friend. As for saving, GetSaveFileName() is indeed similar to the open dialog. Then use WriteFile() to save the content.

One thing I learned the hard way: always, always close your file handles with CloseHandle(). I had a nasty memory leak once because I forgot this step.

Also, consider using std::fstream for file operations. It’s part of the C++ standard library and can make your life much easier, especially when dealing with text files. It handles a lot of the low-level stuff for you.

3

To read the file contents, you’ll want to use ReadFile() after CreateFile(). Allocate a buffer, read the file into it, then use SetWindowText() to display in your text box. For saving, implement GetSaveFileName() similar to your open dialog, then use WriteFile() to write the content.

Here’s a tip: Always check return values and handle errors. File operations can fail for various reasons (permissions, disk full, etc.). Proper error handling will make your app more robust.

For large files, consider reading in chunks or memory mapping for better performance. And don’t forget to close your file handles with CloseHandle() when you’re done to avoid resource leaks.

4

hey there! for reading the file, you can use ReadFile() function after CreateFile(). then use SetWindowText() to display in ur textbox. for saving, GetSaveFileName() works similar to open dialog. WriteFile() to write content. hope this helps! lemme know if u need more details :slight_smile: