未显示我在C++中创建的窗口

#include <windows.h>

LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
    switch (uMsg)
    {
        case WM_PAINT:
        {
            PAINTSTRUCT ps;
            HDC hdc = BeginPaint(hwnd, &ps);
            // 在窗口上绘制图形
            // ...
            EndPaint(hwnd, &ps);
            break;
        }
        case WM_DESTROY:
            PostQuitMessage(0);
            return 0;
    }
    return DefWindowProc(hwnd, uMsg, wParam, lParam);
}

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{
    // 1. 导入必要的头文件和库
    // ...

    // 2. 定义窗口类
    WNDCLASS wc = {};
    wc.lpfnWndProc = WindowProc;
    wc.hInstance = hInstance;
    wc.lpszClassName = "MyWindowClass";

    // 3. 注册窗口类
    RegisterClass(&wc);

    // 4. 创建窗口
    HWND hwnd = CreateWindow(
        "MyWindowClass",    // 窗口类名
        "My Window",        // 窗口标题
        WS_OVERLAPPEDWINDOW,    // 窗口样式
        CW_USEDEFAULT, CW_USEDEFAULT,    // 窗口位置
        500, 400,    // 窗口大小
        NULL, NULL, hInstance, NULL);

    if (hwnd == NULL)
    {
        return 0;
    }

    // 5. 处理窗口消息
    MSG msg = {};
    while (GetMessage(&msg, NULL, 0, 0))
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }

    return msg.wParam;
}