Handling concurrency exceptions when passing the objects ids and timestamps using jQuery - entity-framework

Question

I have the following business scenario inside my Asp.net MVC 4 asset management system :-
Scenario 1) A user selects multiple servers , then he selects a Rack Tag ,and click on
assign . so the selected servers will be assigned to the new Rack.
Scenario 2) And i want to check for any concurrency exception , if for example the selected
servers have been modified by another user since they were retrieved .
so i have wrote the following jQuery which will send the object ids+timestamps to the action method:-
$('body').on("click", "#transferSelectedAssets", function () {
var boxData = [];
$("input[name='CheckBoxSelection']:checked").each(function () {
boxData.push($(this).val());
});
var URL = "#Url.Content("~/Server/TransferSelectedServers")";
$.ajax({
type: "POST",
url: URL,
data: { ids: boxData.join(","), rackTo: $("#rackIDTo").val()}
,
success: function (data) {
addserver(data); })});
and inside the action method i have the following code:-
public ActionResult TransferSelectedServers(string ids, int? rackTo)
{
if (ModelState.IsValid)
{
try
{
var serverIDs = ids.Split(',');
int i = 0;
foreach (var serverinfo in serverIDs)
{
var split = serverinfo.Split('~');
var name = split[0];
//System.Text.ASCIIEncoding encoding = new System.Text.ASCIIEncoding();
byte[] bytearray = Encoding.Default.GetBytes(split[1]);
i++;
var server = repository.FindServer_JTechnology(Int32.Parse(name));
if (server == null)
return Json(new { IsSuccess = false, reload = true, description = " Some Servers might have been deleted, Transferre process has been cancelled .", rackid = rackFrom }, JsonRequestBehavior.AllowGet);
server.RackID = rackTo;
server.timestamp = bytearray;
string ADusername = User.Identity.Name.Substring(User.Identity.Name.IndexOf("\\") + 1);
repository.InsertOrUpdateServer(server, ADusername, server.Technology.IT360ID.Value, server.IT360SiteID, new bool(), server.Technology);
}
repository.Save();
return Json(new { IsSuccess = true, description = i + " Server/s Transferred Successfully To Rack " + }, JsonRequestBehavior.AllowGet);
}
catch (DbUpdateConcurrencyException e)
{
return Json(new { IsSuccess = false, reload = true, description = "records has been modified by antoehr user" }, JsonRequestBehavior.AllowGet);
}
catch (Exception e)
{
return Json(new { IsSuccess = false, reload = true, description = " Server/s Can not Be Transferred to the Selected Rack " }, JsonRequestBehavior.AllowGet);
}
}
return RedirectToAction("Details", new { id = rackTo });
}
and the repository method looks as follow:-
public void InsertOrUpdateServer(TMSServer server, string username, long assetid, long? siteid = 0, bool isTDMHW = false, Technology t = null)
{
server.IT360SiteID = siteid.Value;
tms.Entry(server).State = EntityState.Modified;
var technology = tms.Technologies.Single(a => a.TechnologyID == server.TMSServerID);
technology.IsManaged = t.IsManaged;
tms.Entry(technology).State = EntityState.Modified;
InsertOrUpdateTechnologyAudit(auditinfo);
}
}
but currently if two users selects the same servers and assign them to tow different racks , no concurrency exception will be raised ?
Can anyone advice ? baring in mind that if two users edit single object then one of them will get an concurrent exception message. so my timestamp column is defined correctly.
Thanks