Inserting Related Records into Database via Entity Framework

Question

I'm curious if there is a clean way to do this

Product product = new Product();
product.CreateDateTime = DateTime.Now;
product.Description = productCreateModel.Product.Description;
product.ManufacturerId = productCreateModel.Manufacturer;
product.MetaDescription = productCreateModel.Product.MetaDescription;
product.MetaTitle = productCreateModel.Product.MetaTitle;
product.Name = productCreateModel.Product.Name;
product.Status = ProductStatuses.Active;
product.URL = productCreateModel.Product.URL;

if (productCreateModel.ProductImage1.ContentLength > 0)
    {
        BinaryReader binaryReader = new BinaryReader(productCreateModel.ProductImage1.InputStream);
                product.ProductImages.Add(new ProductImage()
                {
                    CreateDateTime = DateTime.Now,
                    Image = binaryReader.ReadBytes(productCreateModel.ProductImage1.ContentLength),
                    PrimaryImage = true
                });
    }
db.Products.Add(product);
db.SaveChanges();

The problem i'm running into is that the product.ProductImages is null - I'd love to be able to do it this way INSTEAD of doing multiple db.TableName.Add/db.SaveChanges because if I understand it correctly EF creates a transaction so that if anything fails you won't have phantom product records inserted with no product images - if that makes sense?

I'm pretty sure you can do it with only a single db.SaveChanges(), no matter how many objects you've added or what their relationships are. — Bobson
– Bobson, Commented Oct 5, 2012 at 15:06

Raphaël Althaus · Accepted Answer · 2012-10-05 14:54:36Z

4

change your Product Model ?

private IList<ProductImage> productImages_;
public virtual IList<ProductImage> ProductImages {
   get {
     return productImages_ ?? (productImages_= new List<ProductImage>());
   }
   set { productImages_ = value;}
}

answered Oct 5, 2012 at 14:54

Raphaël Althaus

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2 Comments

99823 Over a year ago

this worked perfectly - I didn't think it would work as I was using Code First and wasn't sure if .net would understand this and still relate it properly to my database - however this was perfect - thanks

Raphaël Althaus Over a year ago

@Loren well, the simple public virtual MyList {get;set;} is often presented in examples, but this way of doing should be preferred, when you need to instanciated the model (and having the "Navigation lists" instanciated).

Ray Saltrelli · Accepted Answer · 2012-10-05 15:10:12Z

0

I'm just brain storming here so don't get upset if this doesn't work, but I think you might need to explicitly add the new ProductImage entity to the db.ProductImages entity set before you link it to the Product entity.

Product product = new Product();
product.CreateDateTime = DateTime.Now;
product.Description = productCreateModel.Product.Description;
product.ManufacturerId = productCreateModel.Manufacturer;
product.MetaDescription = productCreateModel.Product.MetaDescription;
product.MetaTitle = productCreateModel.Product.MetaTitle;
product.Name = productCreateModel.Product.Name;
product.Status = ProductStatuses.Active;
product.URL = productCreateModel.Product.URL;

db.Products.Add(product);

if (productCreateModel.ProductImage1.ContentLength > 0)
    {
        BinaryReader binaryReader = new BinaryReader(productCreateModel.ProductImage1.InputStream);

        ProductImage image = new ProductImage()
        {
              CreateDateTime = DateTime.Now,
              Image = binaryReader.ReadBytes(productCreateModel.ProductImage1.ContentLength),
              PrimaryImage = true
        }

        db.ProductImages.Add(image); // Add the image to the ProductImage entity set
        product.ProductImages.Add(image); // link the image to this Product
    }

db.SaveChanges(); // Save all changes

answered Oct 5, 2012 at 15:10

Ray Saltrelli

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3 Comments

Raphaël Althaus Over a year ago

hmmm, the problem is not there, it's just that product.ProductImages (the "navigation list" from the model Product) is not instanciated... And it's hard to add an item to a null List ;)

Ray Saltrelli Over a year ago

Then you must be getting a NullReferenceException when you call db.ProductImages.Add(), correct?

99823 Over a year ago

Yea correct - the thing about this though is I know i can do it this way I was just trying to keep it cleaner by not having to do all the db.tablename.adds - know what i mean? thanks for the try tho! Raphael's solution did the trick

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