Undefined reference errors

I have run into this undefined reference error more than once. I dont know where to go from here. How do I solve an undefined reference error?The code is from a the zetcode website and the reason I'm studying it is because it shows the use of the OPENFILENAME structure. Any help would be greatly appreciatedThanks C:\Users\Neferkamichael\codebprojects\Menu_Sample\open.open.c|| undefined reference to `GetOpenFileNameA@4'|
||=== Build finished: 1 errors, 0 warnings ===|
#include <windows.h>LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);void CreateMenubar(HWND);void OpenDialog(HWND);void LoadFile(LPSTR);#define IDM_FILE_NEW 1HWND ghwndEdit;int WINAPI WinMain( HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow ){ MSG msg ; WNDCLASS wc = {0}; wc.lpszClassName = TEXT( "Opendialog" ); wc.hInstance = hInstance ; wc.hbrBackground = GetSysColorBrush(COLOR_3DFACE); wc.lpfnWndProc = WndProc ; wc.hCursor = LoadCursor(0, IDC_ARROW); RegisterClass(&wc); CreateWindow( wc.lpszClassName, TEXT("Opendialog"), WS_OVERLAPPEDWINDOW | WS_VISIBLE, 150, 150, 265, 200, 0, 0, hInstance, 0); while( GetMessage(&msg, NULL, 0, 0)) { DispatchMessage(&msg); } return (int) msg.wParam;}LRESULT CALLBACK WndProc( HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam ){ switch(msg) { case WM_CREATE: ghwndEdit = CreateWindowEx(WS_EX_RIGHTSCROLLBAR, TEXT("edit"), NULL, WS_VISIBLE | WS_CHILD | WS_HSCROLL | WS_VSCROLL | ES_MULTILINE, 0, 0, 260, 180, hwnd, (HMENU) 1, NULL, NULL); CreateMenubar(hwnd); break; case WM_SIZE: SetWindowPos(ghwndEdit, NULL, 0, 0, LOWORD(lParam), HIWORD(lParam), SWP_NOMOVE | SWP_NOZORDER); break; case WM_COMMAND: if (wParam==IDM_FILE_NEW) { OpenDialog(hwnd); } break; case WM_DESTROY: PostQuitMessage(0); break; } return DefWindowProc(hwnd, msg, wParam, lParam);} void CreateMenubar(HWND hwnd) { HMENU hMenubar; HMENU hMenu; hMenubar = CreateMenu(); hMenu = CreateMenu(); AppendMenu(hMenubar, MF_POPUP, (UINT_PTR)hMenu, TEXT("&File")); AppendMenu(hMenu, MF_STRING, IDM_FILE_NEW, TEXT("&Open")); SetMenu(hwnd, hMenubar);}void OpenDialog(HWND hwnd) { OPENFILENAME ofn; TCHAR szFile[MAX_PATH]; ZeroMemory(&ofn, sizeof(ofn)); ofn.lStructSize = sizeof(ofn); ofn.lpstrFile = szFile; ofn.lpstrFile[0] = '\0'; ofn.hwndOwner = hwnd; ofn.nMaxFile = sizeof(szFile); ofn.lpstrFilter = TEXT("All files(*.*)\0*.*\0"); ofn.nFilterIndex = 1; ofn.lpstrInitialDir = NULL; ofn.lpstrFileTitle = NULL; ofn.Flags = OFN_PATHMUSTEXIST | OFN_FILEMUSTEXIST; if(GetOpenFileName(&ofn)) LoadFile(ofn.lpstrFile);}void LoadFile(LPSTR file){ HANDLE hFile; DWORD dwSize; DWORD dw; LPBYTE lpBuffer = NULL; hFile = CreateFile(file, GENERIC_READ, 0, NULL, OPEN_EXISTING, 0, NULL); dwSize = GetFileSize(hFile, NULL); lpBuffer = (LPBYTE) HeapAlloc(GetProcessHeap(), HEAP_GENERATE_EXCEPTIONS, dwSize + 1); ReadFile(hFile, (LPWSTR)lpBuffer, dwSize, &dw, NULL); CloseHandle(hFile); lpBuffer[dwSize] = 0; SetWindowText(ghwndEdit, (LPSTR) lpBuffer); HeapFree(GetProcessHeap(), 0, lpBuffer);}