linq join with groups

Question

Hej, i've got a problem with linq expression. I Would like to perform join with groups of some set. This is basicly what I need:

var f = new IEnumerable<SomeClass> { ... };
var rows = new IEnumerable<SomeOtherClass> { ... };
var makedGroups = rows.GroupBy(row => row.SomeId);
var groupsJoined = (from row in makedGroups
    join allocQuant in f on row.Key.Value equals allocQuant.SomeId into gj
    select gr => new { Count = gr.Count(), Group = gj });

error is: Error 202 The type of one of the expressions in the join clause is incorrect. Type inference failed in the call to 'Join'.

How to write this expression properly?

What you are looking for is GroupJoin. Consider this [post](http://stackoverflow.com/a/15599143/1039635) — Iurii Khrystiuk, Oct 29 '14 at 08:19
Hi if you found the answer helpful perhaps accepting it as the answer ? — krystan honour, Oct 30 '14 at 10:43

krystan honour · Answer 1 · 2014-10-29T12:26:25.653

I have included some sample code which is doing what you are trying to do. Its adapted from some sample code to use two classes rather than a static array of strings.

The result will yield an IEnumerable With a ProductCategory Field, Products Field which contains groupings of products based on the category and the last column is the count in the grouping.

From what you asked this is what I thought you wanted.

class Product
{

    public Product(string cat, string name)
    {
        Category = cat;
        ProductName = name;
    }

    public string Category { get; set;}
    public string ProductName { get;set;}
}


class ProductClass
{
    public ProductClass (string type)
    {
        ProductType = type;
    }   

    public string ProductType { get;set;}
}

ProductClass[] productClasses = new ProductClass[]{  
    new ProductClass("Beverages"),   
    new ProductClass("Condiments"),   
    new ProductClass("Vegetables"),   
    new ProductClass("Dairy Products"),   
    new ProductClass("Seafood") };  

List<Product> products = new List<Product>();
products.Add(new Product("Seafood", "crab sticks"));
products.Add(new Product("Seafood", "lobster"));
products.Add(new Product("Vegetables", "cucumber"));
products.Add(new Product("Seafood", "oysters"));
products.Add(new Product("Condiments", "pepper"));
products.Add(new Product("Condiments", "salt"));

var query =
    from pc in productClasses
    join product in products on pc.ProductType equals product.Category into gj
    select new { ProductCategory= pc.ProductType, Products = gj, Count = gj.Count() };

Your answer and Iurii Khrystiuk are usefull, I noticed I just made bad query with improper order. — Puchacz, Oct 29 '14 at 19:41

linq join with groups

1 Answers1