A 1-n mapping means that a parent object can have multiple child objects. In the Northwind example, the relationship between Supplier and Product is 1-n, since 1 Supplier can have many (n) Products. Let's continue building on our original example by adding a Supplier class. For now, we'll keep it simple:

using System;
using System.Collections;
using Adapdev.Text;
using System.Collections.Generic;
using Elementary.Attributes;

namespace Elementary.Northwind.Samples.Attributes.ChildMappingOneToNGenericInferred
{
    [ElementaryClass]
	public class Supplier
	{
        [Persist]
		public String CompanyName = "";
        
        [Persist]
		public int SupplierID = 0;

        [HasMany(typeof(Product))]
		public IList<Product> Products = null;

		public override string ToString() 
		{
			return StringUtil.ToString(this);
		}
	}
}

Now, let's write a test to make sure it works:

using System;
using System.Collections.Generic;
using System.Transactions;
using Elementary;
using Elementary.Northwind.Samples;
using NUnit.Framework;

namespace Elementary.Northwind.Samples.Attributes.ChildMappingOneToNGenericInferred
{
	/// <summary>
	/// Summary description for Test.
	/// </summary>
	[TestFixture]
	public class Test
	{
		[TestFixtureSetUp]
		public void SetUp()
		{
			Elementary.Clear();
            Elementary.LoadAssembly("Elementary.Northwind.Samples.dll");
		}
=
		[Test]
		public void GetObjectWithChildren()
		{
			IObjectMapper mapper = Elementary.GetIObjectMapper<Supplier>();
			
			// Retrieve supplier #1
			Supplier supplier = mapper.GetObjectWithChildren(1);

			Console.WriteLine(supplier);
			Console.WriteLine("Products for " + supplier.CompanyName + ":");
			foreach(Product product in supplier.Products)
			{
				Console.WriteLine(product.ProductName);
			}
		}
	}
}

This results in the following output:

Properties for: Supplier
	CompanyName(System.String): Exotic Liquids
	SupplierID(System.Int32): 1
	Products(System.Collections.Generic.IList`1
[Elementary.Northwind.Samples.Attributes.ChildMappingOneToNGenericInferred.Product]): 
System.Collections.Generic.List`1
[Elementary.Northwind.Samples.Attributes.ChildMappingOneToNGenericInferred.Product]

Products for Exotic Liquids:
Chai
Chang
Aniseed Syrup

All of the operations that are available for 1-1 mappings are also available for 1-n mappings. You can retrieve ALL Suppliers and their child Products. You can also add or update a Supplier and it's children. Let's look at example where we'll add a new Product and modify an existing one.

		[Test]
		public void SaveWithChildrenAndUpdateChild()
		{
			IObjectMapper<Supplier> mapper = Elementary.GetIObjectMapper<Supplier>();

			// Get an existing Supplier
			Supplier supplier = mapper.GetObjectWithChildren(1);

			// Track the number of products assigned
			int count = supplier.Products.Count;
			
			// Add a new product
			Product product = new Product();
			product.CategoryID = 1;
			product.ProductName = "Test Product";
			product.SupplierID = 1;

			supplier.Products.Add(product);

			// Modify an existing product
			Product p = supplier.Products[0];
			int pId = p.ProductID;
			p.ProductName = "Bogus";

			// Run in a transaction and rollback so that database changes aren't saved
			using(TransactionScope scope = new TransactionScope())
			{
				mapper.SaveWithChildren(supplier);
				
				Supplier supplier2 = mapper.GetObjectWithChildren(1) as Supplier;

				// Make sure the new product was added
				int newCount = supplier2.Products.Count;
				Assert.AreNotSame(count, newCount, "Object wasn't saved.");
				Assert.AreEqual(newCount, count+1, "Invalid save.");

				// Make sure the modified product was updated
				Assert.AreEqual("Bogus", (supplier2.Products[0] as Product).ProductName, "Child wasn't updated.");
			}
		}

In the example above, we did the following:

using System;
using System.Collections;
using Adapdev.Text;
using System.Collections.Generic;
using Elementary.Attributes;

namespace Elementary.Northwind.Samples.Attributes.ChildMappingOneToNGenericInferred
{
    [ElementaryClass]
	public class Supplier
	{
        [Persist]
		public String CompanyName = "";
        
        [Persist]
		public int SupplierID = 0;

        [HasMany(typeof(Product))]
		public IList<Product> Products = null;

		public override string ToString() 
		{
			return StringUtil.ToString(this);
		}
	}
}

SELECT ProductId, ProductName, SupplierId, CategoryId
FROM Products
WHERE Products.SupplierId = @supplierId
' childColumn maps to Products.SupplierId
' parentColumn maps to Suppliers.SupplierId, which results in the value for @supplierId 

using System;
using System.Collections;
using Adapdev.Text;
using System.Collections.Generic;
using Elementary.Attributes;

namespace Elementary.Northwind.Samples.Attributes.ChildMappingOneToNGeneric
{
    [ElementaryClass(Table="suppliers")]
	public class Supplier
	{
        [Persist]
        public String CompanyName = "";
        [Persist]
        public int SupplierID = 0;

		[HasMany(typeof(Product),
                ChildColumn="supplierid", ParentColumn="supplierid")]
        public IList<Product> Products = null;

		public override string ToString() 
		{
			return StringUtil.ToString(this);
		}
	}
}