请求高手看下代码哪不对

#include <Windows.h>


//函数声明
LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wparam, LPARAM Iparam);


//hInstance 实例句柄，每一个应用程序都是有一个应用程序的实例句柄(唯一的)
//IpCmdLIne 命令行的参数
//nShowCmd 用来指定窗口如何显示，最大化，还是最小化
int WINAPI WinMain(_In_ HINSTANCE hInstance, _In_opt_ HINSTANCE hPrevInstance, _In_ LPSTR lpCmdLine, _In_ int nShowCmd)
{
    //MessageBox(NULL, L"Hello你好Windows", L"新建窗口",MB_OK);


    //1.设计窗口
    WNDCLASSEX wndClass = {};
    wndClass.cbSize = sizeof(WNDCLASSEX);
    wndClass.IpszClassName = L"myclassname";
    wndClass.IpfnWndProc = WndProc;
    wndClass.hInstance = hInstance;

    //2.注册窗口
    if (RegisterClassEx(&wndClass) == false)
    {
        return -1;
    }

    //3.创建窗口
    HWND hwnd = CreateWindow(L"myclassname", L"第一个窗口", WS_OVERLAPPEDWINDOW, CW_USEDEFAULT, CW_USEDEFAULT, 800, 600, NULL, NULL, hInstance, NULL);


    //4.显示窗口
    ShowWindow(hwnd, nShowCmd);
    UpdateWindow(hwnd);

    //5.处理消息
    MSG msg = {0};
    while (msg.message!=WM_QUIT)
    {
        if (PeekMessage(&msg, 0, NULL, NULL, PM_REMOVE))
        {
            //true取得消息
            TranslateMessage(&msg);
            //交给wndproc处理
            DispatchMessage(&msg);
        }
    }

    //注销窗口
    UnregisterClass(L"myclassname", hInstance);
    return 0;
}


//用来处理窗口的时间(比如 键盘按键 鼠标时间 窗口关闭)
LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wparam, LPARAM Iparam)
{
    switch (message)
    {
    default:
        return DefWindowProc(hwnd, message, wparam, Iparam);
    }
    return 0;
}