why it throws an exception when i tried to save a user? - asp.net-mvc-4

Question

This related to my previous post, even though it was original posted as this post it ran in to another problem to which it was answered. So to avoid complexity i have decided to re-post it with a confirmed single error!
i have the following Create() post method to save a user to mst_users table.
[HttpPost]
public ActionResult Create(CustomerVM custObject)
{
if ( ModelState.IsValid )
{
mst_users user = new mst_users
{
uName=custObject.User,
password=custObject.Password,
dtCreated=DateTime.UtcNow,
isLocked=false
};
db.mst_users.Add(user);
db.SaveChanges();
}
}
}
when the methods executes at db.SaveChanges() it throws the error Object is not set an instance of an object but i have initialzed all required fields for the table but it shows me a field in a view that belongs to another collection but its not part of users table here is the video
here is the user object:
here is the error:
Object reference not set to an instance of an object.
Source of the error
Line 44: </div>
Line 45: <div class="editor-field">
Line 46: #Html.DropDownListFor(model => model.NameTitle, Model.NameTitleColl)
Line 47: #Html.ValidationMessageFor(model => model.NameTitle)
Line 48: </div>
Here is the stack:
[NullReferenceException: Object reference not set to an instance of an object.]
ASP._Page_Views_Customer_Create_cshtml.Execute() in c:\aspmvc4-test\test1\test1\Views\Customer\Create.cshtml:46
System.Web.WebPages.WebPageBase.ExecutePageHierarchy() +197
System.Web.Mvc.WebViewPage.ExecutePageHierarchy() +96
System.Web.WebPages.StartPage.RunPage() +17
System.Web.WebPages.StartPage.ExecutePageHierarchy() +62
System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage) +76
System.Web.Mvc.RazorView.RenderView(ViewContext viewContext, TextWriter writer, Object instance) +259
System.Web.Mvc.BuildManagerCompiledView.Render(ViewContext viewContext, TextWriter writer) +115
System.Web.Mvc.ViewResultBase.ExecuteResult(ControllerContext context) +294
System.Web.Mvc.ControllerActionInvoker.InvokeActionResult(ControllerContext controllerContext, ActionResult actionResult) +13
System.Web.Mvc.<>c__DisplayClass1a.<InvokeActionResultWithFilters>b__17() +23
System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilter(IResultFilter filter, ResultExecutingContext preContext, Func`1 continuation) +242
System.Web.Mvc.<>c__DisplayClass1c.<InvokeActionResultWithFilters>b__19() +21
System.Web.Mvc.ControllerActionInvoker.InvokeActionResultWithFilters(ControllerContext controllerContext, IList`1 filters, ActionResult actionResult) +175
System.Web.Mvc.Async.<>c__DisplayClass2a.<BeginInvokeAction>b__20() +89
System.Web.Mvc.Async.<>c__DisplayClass25.<BeginInvokeAction>b__22(IAsyncResult asyncResult) +102
System.Web.Mvc.Async.WrappedAsyncResult`1.End() +57
System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeAction(IAsyncResult asyncResult) +43
System.Web.Mvc.<>c__DisplayClass1d.<BeginExecuteCore>b__18(IAsyncResult asyncResult) +14
System.Web.Mvc.Async.<>c__DisplayClass4.<MakeVoidDelegate>b__3(IAsyncResult ar) +23
System.Web.Mvc.Async.WrappedAsyncResult`1.End() +62
System.Web.Mvc.Controller.EndExecuteCore(IAsyncResult asyncResult) +57
System.Web.Mvc.Async.<>c__DisplayClass4.<MakeVoidDelegate>b__3(IAsyncResult ar) +23
System.Web.Mvc.Async.WrappedAsyncResult`1.End() +62
System.Web.Mvc.Controller.EndExecute(IAsyncResult asyncResult) +47
System.Web.Mvc.Controller.System.Web.Mvc.Async.IAsyncController.EndExecute(IAsyncResult asyncResult) +10
System.Web.Mvc.<>c__DisplayClass8.<BeginProcessRequest>b__3(IAsyncResult asyncResult) +25
System.Web.Mvc.Async.<>c__DisplayClass4.<MakeVoidDelegate>b__3(IAsyncResult ar) +23
System.Web.Mvc.Async.WrappedAsyncResult`1.End() +62
System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult) +47
System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.EndProcessRequest(IAsyncResult result) +9
System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +9651796
System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +155

Answer 1

try to do something like this
mst_users user = new mst_users();
user.uName=custObject.User;
user.password=custObject.Password;
user.dtCreated=DateTime.UtcNow;
user.isLocked=false;
db.mst_users.Add(user);
db.SaveChanges();

Answer 2

the problem was solved, even when i tagged the db table dtUpdated as not null and assigned with getDate() i must send a date from client else throws the above error!