Switch语句中未初始化的局部变量- Win32 API

好了，这是我的代码，我将只提供一个函数感觉，其余的不会有任何帮助。这个问题我一直在找，但似乎就是找不出来。

错误:未初始化的本地变量'hTextBox'使用Win32Project2

LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wparam, LPARAM lparam)
{
    HDC hdc;
    RECT rect;
    PAINTSTRUCT ps;
    HWND hTextBox;
    switch (message)
    {
        case WM_CREATE:
            hTextBox = CreateWindow(L"edit", L"", WS_CHILD|WS_VISIBLE|WS_BORDER, 5, 5, 200, 25, hwnd, NULL, NULL, NULL);
            CreateWindow(L"button", L"Click me!", WS_CHILD | WS_VISIBLE, 20, 40, 75, 25, hwnd, (HMENU)1, NULL, NULL);
            break;
        case WM_COMMAND:
            switch (LOWORD(wparam))
            {
            case 1:
                int returnedCharacters = 0;
                returnedCharacters = GetWindowText(hTextBox, &szTextSaved[0], 20);
                break;
            }

        case WM_PAINT:
            hdc = BeginPaint(hwnd, &ps);
            GetClientRect(hwnd, &rect);
            DrawText(hdc, L"This is a text message!", -1, &rect,  DT_CENTER | DT_VCENTER);
            EndPaint(hwnd, &ps);
            break;
        case WM_DESTROY:
            PostQuitMessage(0);
            break;
    }
    return DefWindowProc(hwnd, message, wparam, lparam);
}