Selecting Multiple Rows from DataGridView using Linq

Question

I'm trying to select multiple rows from a DataGridView instead of iterating with a for-each loop.

I can select 1 item using this code:

DataGridViewRow row2 =
     (from DataGridViewRow r in dgView.Rows
     where r.Cells["name"].Value.ToString().Equals("Akins Ford")select r).FirstOrDefault();

But when I try to select multiple rows, using this code:

List<DataGridViewRow> rows2 =
      (from DataGridViewRow r in dgView.Rows
       where r.Cells["status"].Value.ToString().Equals("active")select r);

I got an error:

Error 2 Cannot implicitly convert type 'System.Collections.Generic.IEnumerable' to 'System.Collections.Generic.List'. An explicit conversion exists (are you missing a cast?) C:\Software\Json\Json\Form1.cs 188 18 Json

I get Object reference not set to an instance of an object. error — PiE
– PiE, Commented Mar 7, 2016 at 1:57
Could you try this.... dataGridView1.Rows.Cast<DataGridViewRow>().Where(x => x.Cells["status"].Value.ToString() == "active").ToList().ForEach(x => x.Selected = true); — Chris
– Chris, Commented Mar 7, 2016 at 2:42

Jens Meinecke · Accepted Answer · 2016-03-07 02:31:23Z

4

You need to do a simple wrap around the result:

List<DataGridViewRow> rows2 =
        new List<DataGridViewRow>
        (from DataGridViewRow r in dgView.Rows
         where r.Cells["status"].Value.ToString().Equals("active")
         select r);

This is because the linq code returns an IEnumerable<T> and not List<T>. But you can create a List<T> from an IEnumerable<T> by calling the appropriate constructor:

var list = new List<T>(iEnumerable);

To prevent null reference exceptions you might want to further improve your code thus:

List<DataGridViewRow> rows2 =
        new List<DataGridViewRow>
        (from DataGridViewRow r in dgView.Rows
         where r.Cells["status"]?.Value.ToString().Equals("active")??false
         select r);

I am assuming that you are using VS2015 which allows null propagation

r.Cells["status"]?.Value.ToString().Equals("active")??false

putting the '?' after the Cells["status"] ensures that any null references result in a null. And then the final ??false says, that if we had a null we return false (ie don't include this row).

edited Mar 7, 2016 at 2:31

answered Mar 7, 2016 at 1:04

Jens Meinecke

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4 Comments

juharr Over a year ago

or just use ToList

PiE Over a year ago

The code compiles, but I get the following error: Object reference not set to an instance of an object.

Jens Meinecke Over a year ago

You probably have an exception inside the where clause. Is it possible that the Cell's value can be null?

PiE Over a year ago

Yes, I do have a row that can be null - that fixed it. Thanks!

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