Linq SelectMany Usage

Question

I unable to come up with a linq query for the following scenario.

public class Product
{
    public virtual string ProductName { get; set; }
    public virtual IList<SubProduct> SubProducts { get; set; }
}

public class SubProduct
{
    public string SubProductName { get; set; }

    public int SubProductTypeId { get; set; }
}

public class SubProductType
{
    public int SubProductTypeId{ get; set; }
    public string Description { get; set; }
}

var productList = List<Product>();

var subProductTypeLlist = List<SubProductType>();

I have a list of products and each product has list of SubProducts. I want to get the query to represent {ProductName, Description}. Please suggest how to write linq query.

Answer 1

Something like this should do the trick:

var result = productList
    .SelectMany(p => p.SubProducts
        .Select(sp => new { SubProduct = sp, ProductName = p.ProductName }))
    .Select(sp => 
        new { Description = subProductTypeList
            .Single(spt => spt.SubProduct.SubProductTypeId == sp.SubProductTypeId).Description,
            ProductName = sp.ProductName })

In the SelectMany, we first do a Select on the internal IEnumerable (IList implements IEnumerable) to convert each SubProduct object to an anonymous class holding the SubProduct object and the ProductName. The SelectMany then converts that to a flat list. We then use Select on that list to create a new anonymous class again, where this time, we grab the Description from subProductTypeList. The result is an IEnumerable of an anonymous class with the members Description and ProductName.