Pass Value from View to Controller - MVC

Pass Value from View to Controller - MVC

i have a list of thumbnails for the user can select one of the image.
onclick on the thumbnail open a larger image into a form.
What im trying to do now is send the id of the image selected to my
controller.
Note: im using MVC 4.
how can i do that?
someone can help with this pls?
Thanks in advance:
Here is my code:
@foreach (var p in ViewBag.Images)
{
<li>
<a href="~/Files/@p.Name" onclick="swap(this); return false;">
<img src="~/Files/@p.Name"/>
</a>
</li>
}
when selected is going this img tag in my form:
<img id="main" src="" >
using this javascript for this event:
function swap(image) {
document.getElementById("main").src = image.href;
}
what i have to do now?
i trying with <input type="hidden" name="Img_Id" value="Viewbag.??????"/>
to pass this value to my controller??