Select values from DataGridViewCellCollection using Linq

Question

I have a DataGridViewCellCollection and want to read the values from the cells. Later I want to create a new object, pass in these values as constructor parameters and add them to a list.

        List<Connection> connections = new List<Connection>();

        for (int i = 0; i < dataGridView.Rows.Count; i++)
        {
            DataGridViewCellCollection cells = dataGridView.Rows[i].Cells; // current cellrow
            int firstValue = (int)cells[1].Tag; // convert to int
            int? secondValue = (int?)cells[0].Value; // convert to nullable int
            connections.Add(new Connection(firstValue, secondValue));
        }

        return connections;

Connection itself represents this struct

internal struct Connection
{
    public Connection(int firstID, int? secondID)
    {
        FirstID = firstID;
        SecondID = secondID;
    }

    public int FirstID { get; private set; }
    public int? SecondID { get; private set; }
}

I would like to rewrite this code with Linq but how can I select specific multiple values and cast the result to an object?

Could you please post the class definition of `Connection`? – Rui Jarimba Oct 19 '18 at 12:09 — Rui Jarimba, Oct 19 '18 at 12:09

Karan · Accepted Answer · 2018-10-19T13:06:05.203

3

List<Connection> connections = dataGridView.Rows.OfType<DataGridViewRow>()
             .Select(x => new Connection((int)x.Cells[1].Tag, (int?)x.Cells[0].Value)
             .ToList();

return connections;

As suggested by @Mark Schultheiss, using .Cast<DataGridViewRow> can be faster as below.

List<Connection> connections = dataGridView.Rows.Cast<DataGridViewRow>()
             .Select(x => new Connection((int)x.Cells[1].Tag, (int?)x.Cells[0].Value)
             .ToList();

return connections;

edited Oct 19 '18 at 13:06

answered Oct 19 '18 at 12:17

Karan

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`.Cast()` may be faster since we can assume the rows of that type perhaps? https://stackoverflow.com/q/4015930/125981 – Mark Schultheiss Oct 19 '18 at 12:57
@MarkSchultheiss Thanks for comment. I've updated my answer. – Karan Oct 19 '18 at 13:06

score 1 · Answer 2 · answered Oct 19 '18 at 12:12

1

from row in datagridView.Rows
let cells = row.Cells
let firstValue = (int)cells[1].Tag
let secondValue = (int?)cells[0].Value
select new Connection(firstValue, secondValue)

answered Oct 19 '18 at 12:12

Jonas Høgh

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I'm sorry but `Rows` got no select method. Do I have to convert it? – Oct 19 '18 at 12:16
It should be `dataGridView.Rows.OfType()` instead of `datagridView.Rows` – Rui Jarimba Oct 19 '18 at 12:27
or cast it `.Cast()` – Mark Schultheiss Oct 19 '18 at 12:36

score 1 · Answer 3 · edited Oct 19 '18 at 12:38

1

var connections = dataGridView.Rows.OfType<DataGridViewRow>()
.Select(r => new Connection((int)r.Cells[1].Tag, (int?)r.Cells[0].Value))

edited Oct 19 '18 at 12:38

Mark Schultheiss

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answered Oct 19 '18 at 12:15

Andy

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I just need to convert `Rows` to something that got a `Select` method because `Rows` has no. And I'm not able to convert `Rows` to a list – Oct 19 '18 at 12:21
Well, now I can add comments. Make sure you are using System.Linq :) – Andy Oct 19 '18 at 12:24
1

It should be `dataGridView.Rows.OfType().Select(...)` instead of `datagridView.Rows.Select(..)` – Rui Jarimba Oct 19 '18 at 12:28
I formatted so I could see it easier, Not sure if the OP wants it realized with `.ToList()` but it seems so? – Mark Schultheiss Oct 19 '18 at 12:42
1

@andy fill more/all of your profile out for a few extra points :) – Mark Schultheiss Oct 19 '18 at 13:01
Thanks @RuiJarimba, I missed that part completely. – Andy Oct 20 '18 at 03:20

score 0 · Answer 4 · answered Oct 19 '18 at 12:22

List<Connection> connections = dataGridView.Rows.OfType<DataGridViewRow>()
                                           .Select(CreateConnection)
                                           .ToList();

Or:

var connections = from row in dataGridView.Rows.OfType<DataGridViewRow>()
                  select CreateConnection(row);

Method CreateConnection:

private Connection CreateConnection(DataGridViewRow row)
{
    var firstValue = (int) row.Cells[1].Tag;
    var secondValue = (int?) row.Cells[0].Value;

    return new Connection(firstValue, secondValue);
}

Select values from DataGridViewCellCollection using Linq

4 Answers4