MVC Updates over values with NULL - asp.net-mvc

Question

This is probably very simple for most MVC programmers, so maybe you can help me out. I have a table called Images in the database with nine columns. On my UPDATE, I just have three I want to mess with (ImageName, ImagePath, CourseID). After I post back with UPDATE, it sets the other six columns to NULL. I'm not sure how to handle this in MVC.:
My ViewModel:
public class GalleryViewModel
{
public Image _image { get; set; }
}
My Model:
public partial class Image
{
public int ImageID { get; set; }
public string ImageName { get; set; }
public string ImagePath { get; set; }
public Nullable<int> CourseID { get; set; }
public string UserId { get; set; }
public Nullable<System.DateTime> CreateDate { get; set; }
public string ImageType { get; set; }
public string ImageSize { get; set; }
public string FriendlyName { get; set; }
public virtual Cours Cours { get; set; }
}
My Controller:
[HttpGet]
public ActionResult UploadImageEdit(int? id)
{
if (id == null)
{
return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
}
var model = new GalleryViewModel
{
_image = db.Images.Find(id),
};
return View(model);
}
[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult UploadImageEdit(GalleryViewModel galleryViewModel)
{
if (ModelState.IsValid)
{
db.Entry(galleryViewModel._image).State = EntityState.Modified;
db.SaveChanges();
return RedirectToAction("UploadImageIndex");
}
return View(galleryViewModel);
}

Answer 1

After reading other examples and becoming more familiar with ViewModel to controller, I got the UPDATE to work by doing the following:
[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult UploadImageEdit(int id, GalleryViewModel galleryViewModel)
{
if (ModelState.IsValid)
{
var imageContext = db.Images.Find(id);
imageContext.FriendlyName = galleryViewModel._image.FriendlyName;
db.Entry(imageContext).State = EntityState.Modified;
db.SaveChanges();
return RedirectToAction("UploadImageIndex");
}
return View(galleryViewModel);
}
I hope this helps other folks out!