Allow Employee to mark attendance once per day ASP.NET MVC

I'm new to ASP.NET MVC. In my Attendance management system, There are no. of employees marking their attendance on a daily basis. I want to restrict employee to mark only one attendance per day. I've done a lot of search but nothing find anything accurate.

Here's my Controller Code to Create Attendance

DateTime todayDate = Convert.ToDateTime(DateTime.Now.ToString("dd MM yyyy"));
[Authorize]
public ActionResult Create() {
Employee employee = JsonConvert.DeserializeObject(User.Identity.Name);
return View(new Attendance() { Emp_Id = employee.Emp_Id });
}
[HttpPost]
public ActionResult Create(Attendance attendance)
{
if (ModelState.IsValid)
{
if (attendance.Date =! todayDate)
{
try
{
db.Attendance.Add(attendance);
db.SaveChanges();
}
catch (Exception ex)
{
throw;
}
}
}
return RedirectToAction("Index", "Attendance");
}

And Here's my View Code

@model AttendancePortal2.Models.Attendance
@{
ViewBag.Title = "Index";
}
class="container">
class="navbar-header">
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class="navbar-collapse collapse">

class="nav navbar-nav">

@Html.ActionLink("Log out", "LogOff", "Account")

@using (Html.BeginForm("Create", "Attendance", FormMethod.Post))

{

class="row">

@Html.HiddenFor(model => model.Emp_Id)

class="col-md-3">

Date class="text-danger">*

class="input-group date form_date" data-date="" data-date-format="dd MM yyyy" data-link-field="dtp_input2" data-link-format="yyyy-mm-dd">

@Html.TextBoxFor(model => model.Date, new { @class = "form-control" })

class="input-group-addon">class="glyphicon glyphicon-remove">

class="input-group-addon">class="glyphicon glyphicon-calendar">

Allow Employee to mark attendance once per day ASP.NET MVC

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