Question

$("#photoAlbum").on("mouseenter", ".imagecontainer", function () {
    $(this).find('.controlbar').show("slide", { direction: "down" }, 1000);
}).on("mouseleave", ".imagecontainer", function () {
    $(this).find('.controlbar').hide("slide", { direction: "up" }, 1000);
});

.controlbar is hidden by default

The .imagecontainer div(s) is appended to #photoAlbum div after
an ajax request hence why I am using .on() and not just .hover(function() {}, function(){})

The HTML, drop-backdrop is absolutely positioned.

<div id="photoAlbum" class="tabcontent">

        <div id="drop-backdrop"> 
            <div class="text">Drag files here to upload</div> 
        </div> 
        <canvas id="drop-target"></canvas> 

<div class="imagecontainer"><div class="controlbar" style="visibility: hidden; "><img src="/TreeView/images/delete.png" width="16px" height="16px"></div><img src="/Content/photoAlbums/9/3/539695_t.jpg"></div></div>

Answer 1

you should load jQuery UI library if you want your script to work

or use :

$("#photoAlbum").on("mouseenter", ".imagecontainer", function () {
    $(this).find('.controlbar').slideDown(1000);
}).on("mouseleave", ".imagecontainer", function () {
    $(this).find('.controlbar').slideUp(1000);
});

instead of style="visibility: hidden; " use style="display:none; "