Saving changes/updating existing object in dataset

问题:

Can I do something like the below (which does not work) without having to explicitly set each property of the object. Product is the object that is created by the default model binder from a form submission and ProductInDb is object in the context/database that I wish to override/update. The ProductID primary key is the same on both.

var ProductInDb = context.Products.FirstOrDefault(x => x.ProductID == product.ProductID);

                    ProductInDb = product;

                    context.SaveChanges();

回答1:

You can attach the existing product and set its state as Modified.

If you are using DbContext API

context.Products.Attach(product);
context.Entry(product).State = EntityState.Modified;

context.SaveChanges();

For ObjectContext

context.Products.Attach(product);
context.ObjectStateManager.ChangeObjectState(product, EntityState.Modified);

context.SaveChanges();