function btnShowPhoto_onclick() {
    var imSrc = document.getElementById("ctl00_ctl00_ContentPlaceHolder1_CPH_AdminBody_tbxPhotoLink").value;
    if (imSrc == "") {
        alert("لطفا آدرس عکس را وارد نمایید.");
        return;
    }
    var imgPhoto = document.getElementById("PishPhoto");
    imgPhoto.src = imSrc;
    if (imgPhoto.width > 500)
        imgPhoto.width = 500;
    imgPhoto.style.display = "block";
}