Group Join

public void Linq103()
{
    string[] categories = new string[]{ 
        "Beverages", 
        "Condiments", 
        "Vegetables", 
        "Dairy Products", 
        "Seafood" };
  
    List products = GetProductList();
  
    var q =
        from c in categories
        join p in products on c equals p.Category into ps
        select new { Category = c, Products = ps };
  
    foreach (var v in q)
    {
        Console.WriteLine(v.Category + ":");
        foreach (var p in v.Products)
        {
            Console.WriteLine("   " + p.ProductName);
        }
    }
}

public void Linq103()
{
    List customers = GetCustomerList();
    List suppliers = GetSupplierList();
 
    var custSupQuery = suppliers.GroupJoin(customers, sup => sup.Country, cust => cust.Country, (sup, cs) => new {Key = sup.Country, Items = cs});
                
    foreach (var item in custSupQuery)
    {
        Console.WriteLine(item.Key + ":");
        foreach (var element in item.Items)
        {
            Console.WriteLine("   " + element.CompanyName);
        }
    }
}