Entity 4.1 Updating an existing parent entity with new child Entities?

Well, this is kind of brute-force-attack to update the child collection. EF doesn't have any magic to update the children - which means: adding new children, deleting removed children, updating existing children - by only setting the state of the parent to Modified Basically this procedure forces you to delete the old children also from the database and insert the new one, like so.

I first clear the existing ingredients collection in the product entity and than add the updated list of ingredients again. Well, this is kind of brute-force-attack to update the child collection. EF doesn't have any magic to update the children - which means: adding new children, deleting removed children, updating existing children - by only setting the state of the parent to Modified.

Basically this procedure forces you to delete the old children also from the database and insert the new one, like so: // product is the detached product with the detached new children collection using (var context = new MyContext()) { var productInDb = context.Products. Include(p => p. Ingredients) .

Single(p => p. Id == product. Id); // Update scalar/complex properties of parent context.

Entry(productInDb).CurrentValues. SetValues(product); foreach (var ingredient in productInDb.Ingredients.ToList()) context.Ingredients. Remove(ingredient); productInDb.Ingredients.Clear(); // not necessary probably foreach (var ingredient in product.

Ingredients) productInDb.Ingredients. Add(ingredient); context.SaveChanges(); } The better procedure is to update the children collection in memory without deleting all children in the database: // product is the detached product with the detached new children collection using (var context = new MyContext()) { var productInDb = context.Products. Include(p => p.

Ingredients) . Single(p => p. Id == product.Id); // Update scalar/complex properties of parent context.

Entry(productInDb).CurrentValues. SetValues(product); var ingredientsInDb = productInDb.Ingredients.ToList(); foreach (var ingredientInDb in ingredientsInDb) { // Is the ingredient still there? Var ingredient = product.

Ingredients . SingleOrDefault(i => i.Id == ingredientInDb. Id); if (ingredient!

= null) // Yes: Update scalar/complex properties of child context. Entry(ingredientInDb).CurrentValues. SetValues(ingredient); else // No: Delete it context.Ingredients.

Remove(ingredientInDb); } foreach (var ingredient in product. Ingredients) { // Is the child NOT in DB? If (!ingredientsInDb.

Any(i => i.Id == ingredient. Id)) // Yes: Add it as a new child productInDb.Ingredients. Add(ingredient); } context.SaveChanges(); }.

This works absolutly perfectly! Thx a lot! – DirkDooms Nov 2 at 18:28 Took me long to find how to properly update entities.

Thanks for context. Entry(productInDb).CurrentValues. SetValues(product); – Michal B.

Dec 9 at 13:35.

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