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Alan Ciantar
Alan Ciantar

Reputation: 278

c# - Linking two lists efficiently

I have two lists:

  1. Products
  2. A list of Product and Warehouse combination containing prices/quantities etc.

Two seperate results of sql queries.

The second list has a 'ProductId'.

What I'm currently doing is:

foreach(var product in Products)
     var productWarehouses = Warehouses.Where(x=> x.ProductId == productId).ToList();
     product.Warehouses = productWarehouses;

Thing is, this takes very, very long.

Note: I've tried splitting Products into chunks of lists and using Parallel.Foreach() and Tasks to take the time down - but still takes very long.

Upvotes: 0

Views: 58

Answers (3)

n0rd
n0rd

Reputation: 12670

Create a Dictionary<int, Product> from your Products where Product.ProductID is used as key:

var pd = Products.ToDictionary(p => p.ProductID, p => p);

then you can iterate over Warehouses and lookup appropriate products fast:

foreach (var wh in Warehouses)
{
    pd[wh.ProductId].Warehouses.Add(wh); //supposed Product.Warehouses lists have already been created, if not, add checks and create them as needed.
}

Upvotes: 0

Servy
Servy

Reputation: 203830

Use a Join rather than doing a linear search through the entirety of one collection for each item in the other collection:

var query = from product in Products
    join warehouse in Warehouses
    on product.productId equals warehouse.ProductId
    into warehouses
    select new
    {
        product,
        warehouses,
    };

Upvotes: 1

ashokd
ashokd

Reputation: 393

Instead of doing this in c#, I would prefer to do it in SQL stored procedure. Get all details from one sql and then iterate though result to create Product list.

Upvotes: 0

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