How to check null field column using C# in ASP.Net MVC

Hi Ruben12345,

You can achieve like below by checking whether the vehicleId already exists or not if exists then assign the end time with begin time and in else condition you need to add send end date null you can optimize your code according to your need i have just provided you the way how you can achieve your requirement.

ShipmentAssignment getduplicatevehicle = db.ShipmentAssignments.Where(m => m.vehicle_id == model.vehicle_id ).FirstOrDefault();
if (getduplicatevehicle != null)
{
    ShipmentAssignment shipment = new ShipmentAssignment()
    {
        member_id = memberId,
        partner_id = (int)model.partner_id,
        vehicle_id = (int)model.vehicle_id,
        shipment_no = model.shipment_no,
        begin_date_time = model.begin_date_time,
        create_date = DateTime.Now,
        end_date_time = model.begin_date_time,
        active = true

    };

    db.ShipmentAssignments.Add(shipment);
    db.SaveChanges();
    //Session["UpdateMessage"] = "Vehicle has been assign";
    SetUpdateMessage("Vehicle has been assigned");
    return RedirectToAction("Index");
}
else
{
    ShipmentAssignment shipment = new ShipmentAssignment()
    {
        member_id = memberId,
        partner_id = (int)model.partner_id,
        vehicle_id = (int)model.vehicle_id,
        shipment_no = model.shipment_no,
        begin_date_time = model.begin_date_time,
        create_date = DateTime.Now,        
        active = true

    };

    db.ShipmentAssignments.Add(shipment);
    db.SaveChanges();
    //Session["UpdateMessage"] = "Vehicle has been assign";
    SetUpdateMessage("Vehicle has been assigned");
    return RedirectToAction("Index");
}