演示：開啟一個文字檔案讀取其中的第一個整數

#include <Windows.h>
#include <iostream>
#include <fstream>
using namespace std;

int main()
{
	TCHAR szFileName[MAX_PATH] = {};
	OPENFILENAMEW openFileName = {};
	openFileName.lStructSize = sizeof(OPENFILENAMEW);
	openFileName.nMaxFile = MAX_PATH;//這個必須設定，不設定的話不會出現開啟檔案對話方塊  
	openFileName.lpstrFilter = L"文字檔案（*.txt*）\0*.txt\0任何檔案（*.*）\0*.*\0";
	openFileName.lpstrFile = szFileName;
	openFileName.nFilterIndex = 1;
	openFileName.Flags = OFN_PATHMUSTEXIST | OFN_FILEMUSTEXIST;

	if (GetOpenFileName(&openFileName))// 如果儲存則用GetSaveFileName()
	{
		MessageBox(nullptr, openFileName.lpstrFile, L"", MB_OK);
		std::ifstream fin(openFileName.lpstrFile);
		int a;
		fin >> a;
		fin.close();
		wchar_t buffer[32] = {};
		wsprintf(buffer, L"%d", a);
		MessageBox(nullptr, buffer, L"", MB_OK);
	}

	return 0;
}