void FileOpen(HWND hwnd)
{
    OPENFILENAME ofn;       // common dialog box structure
    char szFile[260];       // buffer for file name
    HANDLE hf;              // file handle

    // Initialize OPENFILENAME
    ZeroMemory(&ofn, sizeof(ofn));
    ofn.lStructSize = sizeof(ofn);
    ofn.hwndOwner = hwnd;
    ofn.lpstrFile = szFile;
    // Set lpstrFile[0] to '\0' so that GetOpenFileName does not
    // use the contents of szFile to initialize itself.
    ofn.lpstrFile[0] = '\0';
    ofn.nMaxFile = sizeof(szFile);
    ofn.lpstrFilter = "All\0*.*\0Text\0*.TXT\0";
    ofn.nFilterIndex = 1;
    ofn.lpstrFileTitle = NULL;
    ofn.nMaxFileTitle = 0;
    ofn.lpstrInitialDir = NULL;
    ofn.Flags = OFN_PATHMUSTEXIST | OFN_FILEMUSTEXIST;

    // Display the Open dialog box.

    if (GetOpenFileName(&ofn)==TRUE)
        hf = CreateFile(ofn.lpstrFile,
                        GENERIC_READ,
                        0,
                        (LPSECURITY_ATTRIBUTES) NULL,
                        OPEN_EXISTING,
                        FILE_ATTRIBUTE_NORMAL,
                        (HANDLE) NULL);
}

#include <windows.h>
void FileOpen(HWND);

int WinMain(HINSTANCE hInstance,
                     HINSTANCE hPrevInstance,
                     LPTSTR    lpCmdLine,
                     int       nCmdShow)
{
    HWND hwnd;
    FileOpen(hwnd);
    return 0;
}

void FileOpen(HWND hwnd)
{
    OPENFILENAME ofn;       // common dialog box structure
    char szFile[260];       // buffer for file name
    HANDLE hf;              // file handle

    // Initialize OPENFILENAME
    ZeroMemory(&ofn, sizeof(ofn));
    ofn.lStructSize = sizeof(ofn);
    ofn.hwndOwner = hwnd;
    ofn.lpstrFile = szFile;
    // Set lpstrFile[0] to '\0' so that GetOpenFileName does not
    // use the contents of szFile to initialize itself.
    ofn.lpstrFile[0] = '\0';
    ofn.nMaxFile = sizeof(szFile);
    ofn.lpstrFilter = "All\0*.*\0Text\0*.TXT\0";
    ofn.nFilterIndex = 1;
    ofn.lpstrFileTitle = NULL;
    ofn.nMaxFileTitle = 0;
    ofn.lpstrInitialDir = NULL;
    ofn.Flags = OFN_PATHMUSTEXIST | OFN_FILEMUSTEXIST;

    // Display the Open dialog box.

    if (GetOpenFileName(&ofn)==TRUE)
        hf = CreateFile(ofn.lpstrFile,
                        GENERIC_READ,
                        0,
                        (LPSECURITY_ATTRIBUTES) NULL,
                        OPEN_EXISTING,
                        FILE_ATTRIBUTE_NORMAL,
                        (HANDLE) NULL);
}

HRESULT SimpleInvoke(HWND hwnd)
{
    IFileDialog *pfd;
    
    // CoCreate the dialog object.
    HRESULT hr = CoCreateInstance(CLSID_FileOpenDialog,
                                  NULL,
                                  CLSCTX_INPROC_SERVER,
                                  IID_PPV_ARG(IFileDialog, &pfd));
    
    if (SUCCEEDED(hr))
    {
        // Show the dialog
        hr = pfd->Show(hwnd);
        
        if (SUCCEEDED(hr))
        {
            // Obtain the result of the user's interaction with the dialog.
            IShellItem *psiResult;
            hr = pfd->GetResult(&psiResult);
            
            if (SUCCEEDED(hr))
            {
                // Do something with the result.
                psiResult->Release();
            }
        }
        pfd->Release();
    }
    return hr;

D:\Users\lanec42\Desktop\Balance1\file.cpp||In function `void FileOpen(HWND__*)':|
D:\Users\lanec42\Desktop\Balance1\file.cpp|8|error: `CLSID_FileOpenDialog' was not declared in this scope|
D:\Users\lanec42\Desktop\Balance1\file.cpp|11|error: `IFileDialog' was not declared in this scope|
D:\Users\lanec42\Desktop\Balance1\file.cpp|11|error: `pfd' was not declared in this scope|
D:\Users\lanec42\Desktop\Balance1\file.cpp|11|error: `IID_PPV_ARG' was not declared in this scope|
D:\Users\lanec42\Desktop\Balance1\file.cpp|21|error: `IShellItem' was not declared in this scope|
D:\Users\lanec42\Desktop\Balance1\file.cpp|21|error: `psiResult' was not declared in this scope|
D:\Users\lanec42\Desktop\Balance1\file.cpp|21|warning: unused variable 'IShellItem'|
||=== Build finished: 7 errors, 4 warnings ===|