this is my question: Let's say I have a block class, and a list of blocks:

List<Block> blocks = new List<Block> ();

Block b1 = new Block ();
b1.id_material = 1;
b1.id_color = 1;
b1.weight = 1.5f;

Block b2 = new Block();
b2.id_material = 2;
b2.id_color = 1;
b2.weight = 3f;

Block b3 = new Block();
b3.id_material = 1;
b3.id_color = 1;
b3.weight = 4.5f;

blocks.Add (b1);
blocks.Add (b2);
blocks.Add (b3);

class Block
{
    public int id_material { get; set; }
    public int id_color { get; set; }
    public float weight { get; set; }
}

As you can see each block has its material, color and weigth. I need to create a new list, where if two or more blocks have the same color and material, it must sum their weights.

In this example, the new list should have two blocks,liko so:

List<Block> new_blocks = new List<Block> ();

Block b1 = new Block ();
b1.id_material = 1;
b1.id_color = 1;
b1.weight = 6f; //1,5   4,5

Block b2 = new Block();
b2.id_material = 2;
b2.id_color = 1;
b2.weight = 3f;

new_blocks.Add(b1);
new_blocks.Add(b2);

Is there a way I can do that ? Thanks!

CodePudding user response：

This can be done using GroupBy using the namespace System.Linq like :

var new_blocks = blocks.GroupBy(x=> 
                                   new 
                                   { 
                                    x.id_material , 
                                    x.id_color  
                                   }
                                 )
                       .Select(x => new Block()
                                        {
                                           id_material = x.Key.id_material,
                                           id_color = x.Key.id_color,
                                           weight = x.Sum(y => y.weight)  
                                        }).ToList();

So we had grouped the blocks based on the id_material and color and then we sum the weight of all the blocks that have same id_material and color

Output:

id_material:1,id_color:1,weight:6
id_material:2,id_color:1,weight:3

For reference see the working DEMO Fiddle here