How To Mapping Entity When Editing it in ASP.Net MVC using AutoMapper

i have a view model like this:

public class CityModel
{
    public int Id { get; set; }

    [Required]
    public int ProvinceId { get; set; }

    [Required]
    public string Caption { get; set; }

    public string Description { get; set; }
}

and an entity:

public class City : BaseEntity
{
    public int ProvinceId { get; set; }
    public string Caption { get; set; }
    public string Description { get; set; }

    public virtual Province Province { get; set; }
}

and a BaseEntity:

public abstract class BaseEntity
{
    public int Id { get; set; }

    public DateTime CreatedOn { set; get; }
    public string CreatedBy { set; get; }

    public DateTime ModifiedOn { set; get; }
    public string ModifiedBy { set; get; }
}

i want to map one object of type CityModel to on object of type City In Edit Action using AutoMapper ,

[HttpPost]
public ActionResult Edit(CityModel model)
{
    if (ModelState.IsValid)
    {
        var entity = _cityRepository.GetCity(model.Id);
        entity = model.ToEntity();
        var operationStatus = _cityRepository.Edit(entity);
        if (operationStatus.IsSuccess) operationStatus = _cityRepository.Save();

        if (operationStatus.IsSuccess)
            RedirectToAction("Index");
    }
    ViewBag.ProvinceId = new SelectList(_provinceRepository.Provinces, "Id", "Caption", model.ProvinceId);
    return View(model);
}

The ToEntity is :

public static City ToEntity(this CityModel model)
{
    return Mapper.DynamicMap<CityModel, City>(model);
}

and finally create map from CityModel To City Uses this Code:

Mapper.CreateMap<CityModel, City>()
              .ForMember(des => des.Caption, op => op.MapFrom(src => src.Caption.ToPersianContent()))
              .ForMember(des => des.Description, op => op.MapFrom(src => src.Description.ToPersianContent()));

when i want to map from CityModel To City , get City From Database. inherited data in city object are correct :

and After Mapping , i want to keep original inherited mapping and automapper ignore mapping this base properties, but null and default values are set to this properties: