尝试将对象与EntityFramework关联时出现无效的列名错误

Question

The entity framework is giving me some trouble.

Here are my tables:

Products

Related Products

And my DB context (part of it, anyway)...

ApplicationContext.cs

public class ApplicationContext : DbContext
{
        public ApplicationContext() : base("DefaultConnection")
        {
        }

        public DbSet<Product> Products { get; set; }
        public DbSet<RelatedProduct> RelatedProducts { get; set; }
}

And the models...

Product.cs

public class Product
{
    public int ID              { get; set; }
    public string Manufacturer { get; set; }
    public string Model        { get; set; }
    public string PartNumber   { get; set; }
    public int CategoryID      { get; set; }
    public string Description  { get; set; }
    public decimal Price { get; set; }

    public virtual ICollection<RelatedProduct> RelatedProducts { get; set; }
}

RelatedProduct.cs

public class RelatedProduct
{
    public int ID        { get; set; }
    public int OwnerID   { get; set; }
    public int ProductID { get; set; }

    public virtual Product Owner { get; set; }
    public virtual Product Product { get; set; }
}

What I am trying to do

Loop through a list of related products like this:

<ul class="activity">
      @foreach (var related in @Model.RelatedProducts)
      {
             <li>
                  <i class="fa fa-chevron-right red"></i> <strong>@related.Product.Manufacturer:</strong> @related.Product.Model
             </li>
      }
</ul>

The Problem

I keep getting this errorL

{"Invalid column name 'Product_ID'.\r\nInvalid column name 'Product_ID'.\r\nInvalid column name 'Product_ID'."}

Any ideas?

Answer 1

You must tell EF if Product.RelatedProducts is the inverse navigation property of RelatedProduct.Owner or of RelatedProduct.Product . Both would be possible and valid and EF can't decide it on its own.

Solution with data annotations (assuming Owner is the inverse of RelatedProducts ):

[InverseProperty("RelatedProducts")]
public virtual Product Owner { get; set; }

public virtual Product Product { get; set; }

Or with Fluent API:

modelBuilder.Entity<RelatedProduct>()
    .HasRequired(r => r.Owner)
    .WithMany(p => p.RelatedProducts)
    .HasForeignKey(r => r.OwnerID);

modelBuilder.Entity<RelatedProduct>()
    .HasRequired(r => r.Product)
    .WithMany()
    .HasForeignKey(r => r.ProductID)
    .WillCascadeOnDelete(false);

Probably only the Fluent API solution will work because you also need to disable cascading delete for one of the relationships which isn't possible with data annotations.

Answer 2

Actually, the problem here was Entity Framework's "conventions over configuration". The convention for a foreign key column, when it is not explicitly added as a property, is to name it [RelatedProperty]_[RelatedClassPK] . In your situation that would be Owner_ID and Product_ID . However, these columns don't exist on your tables, so you get an error. The usual fix is to just tell EF explicitly what your foreign key properties are:

[ForeignKey("Owner")]
public int OwnerID { get; set; }

public virtual Product Owner { get; set; }

With that, Entity Framework looks for an OwnerID column, instead, and all is good. @Slauma inadvertently solved the underlying problem with the Fluent API approach, which explicitly declares the properties to use for the foreign keys with HasForeignKey . This is an equally valid approach, but I felt you should know what was actually your problem.