Updating parent model and all children - asp.net-core

Question

I am creating a simple WebApi for Recipes. A recipe contains both ingredients and instructions. I think I got most of the WebApi down, except for the Update() part.
I am not quite sure if I am doing it the right way. My code looks very long and complicated.
Is there an easier way to update parent and all children?
public async Task<IActionResult> Update(int id, [FromBody] RecipeViewModel recipeViewModel)
{
var recipeToUpdate = _unitOfWork.RecipeRepository.Get(filter: r => r.RecipeId == id,
includeProperties: "Ingredients,Instructions").FirstOrDefault();
recipeToUpdate.Name = recipeViewModel.Name;
recipeToUpdate.Description = recipeViewModel.Description;
recipeToUpdate.Image = recipeViewModel.Image;
foreach (var oldIngredient in recipeToUpdate.Ingredients)
{
var newIngredient = recipeViewModel.Ingredients.Where(ingredient => ingredient.IngredientId == oldIngredient.IngredientId).FirstOrDefault();
if (newIngredient == null)
{
recipeToUpdate.Ingredients.Remove(oldIngredient);
_unitOfWork.IngredientRepository.Delete(oldIngredient);
}
else
{
oldIngredient.Value = newIngredient.Value;
oldIngredient.Name = newIngredient.Name;
oldIngredient.Position = newIngredient.Position;
oldIngredient.Unit = newIngredient.Unit;
_unitOfWork.IngredientRepository.Update(newIngredient);
}
}
foreach (var newIngredient in recipeViewModel.Ingredients)
{
var oldIngredient = recipeToUpdate.Ingredients.Where(ingredient => ingredient.IngredientId == newIngredient.IngredientId).FirstOrDefault();
if (oldIngredient == null)
{
recipeToUpdate.Ingredients.Add(newIngredient);
_unitOfWork.IngredientRepository.Insert(newIngredient);
}
else
{
oldIngredient.Value = newIngredient.Value;
oldIngredient.Name = newIngredient.Name;
oldIngredient.Position = newIngredient.Position;
oldIngredient.Unit = newIngredient.Unit;
_unitOfWork.IngredientRepository.Update(oldIngredient);
}
}
foreach (var oldInstruction in recipeToUpdate.Instructions)
{
var newInstruction = recipeViewModel.Instructions.Where(instruction => instruction.InstructionId == oldInstruction.InstructionId).FirstOrDefault();
if (newInstruction == null)
{
recipeToUpdate.Instructions.Remove(oldInstruction);
_unitOfWork.InstructionRepository.Delete(oldInstruction);
}
else
{
oldInstruction.Position = newInstruction.Position;
oldInstruction.Description = newInstruction.Description;
_unitOfWork.InstructionRepository.Update(oldInstruction);
}
}
foreach (var newInstruction in recipeViewModel.Instructions)
{
var oldInstruction = recipeToUpdate.Instructions.Where(instruction => instruction.InstructionId == newInstruction.InstructionId).FirstOrDefault();
if (oldInstruction == null)
{
recipeToUpdate.Instructions.Add(newInstruction);
_unitOfWork.InstructionRepository.Insert(newInstruction);
}
else
{
oldInstruction.Position = newInstruction.Position;
oldInstruction.Description = newInstruction.Description;
_unitOfWork.InstructionRepository.Update(oldInstruction);
}
}
_unitOfWork.RecipeRepository.Update(recipeToUpdate);
await _unitOfWork.Save()
}
And these are my models and my view model:
public class Recipe
{
public int RecipeId { get; set; }
[DataType(DataType.DateTime)]
[DisplayFormat(DataFormatString = "{0:yyyy-MM-dd HH:mm:ss}")]
public DateTime? CreationDate { get; set; }
[JsonIgnore]
public virtual IdentityUser? Creator { get; set; }
[Required(ErrorMessage = "A recipe must have a name"), MaxLength(254)]
public string? Name { get; set; }
[Required(ErrorMessage = "A recipe must have a description"), MaxLength(254)]
public string? Description { get; set; }
public virtual ICollection<Ingredient>? Ingredients { get; set; }
public virtual ICollection<Instruction>? Instructions { get; set; }
public string? Image { get; set; }
}
public class Ingredient
{
public int IngredientId { get; set; }
public int Position { get; set; }
[Required(ErrorMessage = "An ingredient must have a value")]
public Decimal? Value { get; set; }
[Required(ErrorMessage = "An ingredient must have a unit")]
public string? Unit { get; set; }
[Required(ErrorMessage = "An ingredient must have a name")]
public string? Name { get; set; }
}
public class Instruction
{
public int InstructionId { get; set; }
public int Position { get; set; }
[Required(ErrorMessage = "An instruction cannot be empty")]
public string? Description { get; set; }
}
public class RecipeViewModel
{
[Required(ErrorMessage = "A recipe must have a name"), MaxLength(254)]
public string? Name { get; set; }
[Required(ErrorMessage = "A recipe must have a description"), MaxLength(254)]
public string? Description { get; set; }
public ICollection<Ingredient>? Ingredients { get; set; }
public ICollection<Instruction>? Instructions { get; set; }
public string? Image { get; set; }
}
Appreciate any help, thanks.