Question

Error Message:
An object with the same key already exists in the ObjectStateManager. The ObjectStateManager cannot track multiple objects with the same key.

I want to get Image Url from database if fileupload has null value(not change).
I mean if i change smallImage and not change LargeImage,then it should get largeImage value from DB.

[HttpPost]
    public ActionResult Edit(Blog blog, HttpPostedFileBase smallImage, HttpPostedFileBase largeImage)
    {
        if (ModelState.IsValid)
        {
            if (smallImage != null)
            {
                blog.SmallImage = smallImage.ContentLength + "_" + smallImage.FileName;
                string filepath = Path.Combine(Server.MapPath("~/Content/Blog/"), smallImage.ContentLength + "_" + smallImage.FileName);
                smallImage.SaveAs(filepath);
            }
            else
            {
                blog.SmallImage = db.Blogs.Find(blog.ID).SmallImage;
            }
            if (largeImage != null)
            {
                blog.LargeImage = largeImage.ContentLength + "_" + largeImage.FileName;
                string filepath = Path.Combine(Server.MapPath("~/Content/Blog/"), largeImage.ContentLength + "_" + largeImage.FileName);
                largeImage.SaveAs(filepath);
            }
            else
            {
                blog.LargeImage = db.Blogs.Find(blog.ID).LargeImage;
            }
            blog.PostDate = Convert.ToDateTime(DateTime.Now.ToShortDateString());
            db.Entry(blog).State = EntityState.Modified;
            db.SaveChanges();
            return RedirectToAction("Index");
        }
        return View(blog);
    }

Thank you.

Answer 1

You are both loading a copy of the blog

 db.Blogs.Find(blog.ID)

and attaching another with the same id to the context

db.Entry(blog).State = EntityState.Modified;

meaning you have 2 copies of the same blog in the context (not allowed).

I’d recommend the replacing the one posted back with a viewmodel instead, something like

public ActionResult Edit(BlogViewModel viewModel, HttpPostedFileBase smallImage, HttpPostedFileBase largeImage)
{
    if (!ModelState.IsValid)
    {
        return View(viewModel);
    }
        var blog =  db.Blogs.Find(viewModel.ID);
        if (smallImage != null)
        {
            blog.SmallImage = smallImage.ContentLength + "_" + smallImage.FileName;
            string filepath = Path.Combine(Server.MapPath("~/Content/Blog/"), smallImage.ContentLength + "_" + smallImage.FileName);
            smallImage.SaveAs(filepath);
        }

        if (largeImage != null)
        {
            blog.LargeImage = largeImage.ContentLength + "_" + largeImage.FileName;
            string filepath = Path.Combine(Server.MapPath("~/Content/Blog/"), largeImage.ContentLength + "_" + largeImage.FileName);
            largeImage.SaveAs(filepath);
        }


        blog.Title = viewModel.Title;
        blog.Body = viewModel.Body; //etc

        db.SaveChanges();
        return RedirectToAction("Index");
}