CODEWITHSUNDEEP
c#linqlinq-to-sql
Mauro
Mauro

Reputation: 2070

LINQ Select a List of List with DISTINCT

imagine to have a class (and corresponding db table) as follows

class Price{
    int ItemID;
    int ItemTypeID;
    string ItemName;
    string ItemTypeName;
    float Price;
}

I am seraching for a new to query it via LINQ in order to get the list of distinct Items (possibly with the use of Take() and Skip() methods) and nested the list of all associated prices.

Any suggestion?

EDIT: To make the question simpler here's an example

Imagine to have 3 "prices" as following

1, 1, Ball, Blue, 10 
1, 2, Ball, Red,  20 
2, 1, Frisbee, Blue, 30

I would like to put them in a simplified structure

List<Item>

where 

class Item
{
    string ItemName;
    string ItemTypeName;
    List<Price> Prices;
}

and

class Price
{
    float Price;
}

Upvotes: 1

Views: 3868

Answers (2)

Mahmoud Gamal
Mahmoud Gamal

Reputation: 79929

Use Distinct(), like this:

var results = _dbContext.Prices
    .Distinct()
    .Skip(15)
    .Take(5);

Edit: To populate List<Item> with a list of prices for each item as you asked you should use a GROUPBY like this:

var results = _dbContext.GroupBy( i => new { i.ItemName, i.ItemTypeName })
    .Select( g => new Item()
        {
            ItemName = g.Key.ItemName,
            ItemTypeName = g.Key.ItemTypeName,
            Prices = g.Select( p => new Price(){Price = p.Price})
         });

After that you can applay Take and Skip the same way as in the first query.

Upvotes: 5

cadrell0
cadrell0

Reputation: 17307

It sounds like maybe you want a GroupBy. Try something like this.

var result = dbContext.Prices
    .GroupBy(p => new {p.ItemName, p.ItemTypeName)
    .Select(g => new Item
                     {
                         ItemName = g.Key.ItemName,
                         ItemTypeName = g.Key.ItemTypeName,
                         Prices = g.Select(p => new Price 
                                                    {
                                                        Price = p.Price
                                                    }
                                           ).ToList()

                     })
     .Skip(x)
     .Take(y)
     .ToList();

Upvotes: 5

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