[WinAPI] error LNK2019: unresolved external symbol __imp__RegisterClassExA@4

#ifndef MAIN_HPP_INCLUDED
#define MAIN_HPP_INCLUDED
#include <windows.h>

LRESULT CALLBACK WndProc( HWND hwnd,
UINT msg,
WPARAM wParam,
LPARAM lParam )
{
    switch( msg )
    {
    case WM_KEYDOWN:
        if( wParam == VK_ESCAPE ) {
            DestroyWindow( hwnd );
        }
        return 0;
       
    case WM_DESTROY:
        PostQuitMessage( 0 );
        return 0;
    }
    return DefWindowProc( hwnd,
    msg,
    wParam,
    lParam );
}

WNDCLASSEX Start( WNDCLASSEX WiTP, HINSTANCE hInstance ) //WiTP - Window To Prepare
{
    WNDCLASSEX WiP_Clone = WiTP; // WiP_Clone - Window To Prepare_Clone
   
    ZeroMemory( & WiP_Clone, sizeof( WNDCLASSEX ) );
    WiP_Clone.cbSize = sizeof( WNDCLASSEX );
    WiP_Clone.style = CS_CLASSDC;
    WiP_Clone.lpfnWndProc = WndProc;
    WiP_Clone.hInstance = hInstance;
    WiP_Clone.hCursor = LoadCursor( NULL, IDC_ARROW );
    WiP_Clone.lpszClassName =( "MainGameWndClass" );
    RegisterClassEx( & WiP_Clone );
    return WiP_Clone;
}

HWND CreateNewWindow( LPSTR WindowClassName, LPSTR WindowName, HINSTANCE hInstance, int width, int height )
{
    HWND hWnd = CreateWindow(
    ( WindowClassName ),
    ( WindowName ),
    WS_SYSMENU,
    CW_USEDEFAULT, CW_USEDEFAULT,
    width, height,
    NULL, NULL,
    hInstance,
    NULL );
    ShowWindow( hWnd, SW_SHOWDEFAULT );
    return hWnd;
}

#endif // MAIN_HPP_INCLUDED