body.DataContext.Loading>div {
    display: none;
}

body.DataContext:before
{

    width: 25px;
    height: 25px;
    position: absolute;
    top: 50%;
    left: 50%;
    margin-top: -13px;
    margin-left: -13px;
    content: '';
    background-image: url(imgs/loading.gif);
    background-size: 100% 100%;
    background-position: center center;
    display: none;

}

body.DataContext.Loading:before
{
    display: block;
}