Merge.cs

// create a new Order 
Order order = new Order()
{
    Customer = new Customer() { Name = "Peter Customer" }
};

// create a new ProductBlock
ProductBlock block = new ProductBlock();
block.Products = new List<Product>()
{
   new Product() { Name = "Product 1", Price = 200 },
   new Product() { Name = "Product 2", Price = 400 },
   new Product() { Name = "Product 3", Price = 800 }
};

// add the ProductBlock to the ObservableCollection
order.ProductBlocks.Add(block);

// create a second ProductBlock
ProductBlock block2 = new ProductBlock();
block2.Products = new List<Product>()
{
   new Product() { Name = "Product 4", Price = 231 },
   new Product() { Name = "Product 5", Price = 32424 },
   new Product() { Name = "Product 6", Price = 33 },
   new Product() { Name = "Product 7", Price = 332 },
};

order.ProductBlocks.Add(block2);

// merge the template with the business object
using (MailMerge mailMerge = new MailMerge())
{
    mailMerge.TextComponent = textControl1;
    mailMerge.MergeObject(order);
}