Passing DataGridViewRow as referance

Question

I want to pass DataGridviewRow as a ref where i am assigning some value to its cells but i am unable to do this

foreach(DataGridViewRow dgr in dgvMarksEntryByClassWise.Rows)
{
   RowValueSet(ref dgr);
}

Here it is giving Compile time Error because dgr is an foreach iteration variable
Also i tried to do it with for loop

for (int i = 0; i < dgvMarksEntryByClassWise.Rows.Count; i++)
{
  RowValueSet(ref dgvMarksEntryByClassWise.Rows[i]);
}

But here also it is giving Compile time error:
A property,indexer or dynamic member acces cannot passed as an out reference

I referd this question asked on above errors but did't Found any appropriate solution of my problem

Please Suggest me how to Do this

Update Code

void RowValueSet(ref DataGridViewRow dgr)
{
dgr.Cells["StudentZero"].Value = ss.Where(w => w.MarksheetMarks == "0").Count();
if (ss.Count() != 0)
dgr.Cells["StudentISEmpty"].Value = Convert.ToInt16(lblTotlatStudent1.Text) - ss.Count();
else
dgr.Cells["StudentISEmpty"].Value = 0;
dgr.Cells["StudentEntry"].Value = ss.Count();
}

There's no reason RowValueSet needs the row passed by ref. Just pass it in, your code should work fine. — DaveShaw, Feb 11 '14 at 08:29
Just remove `ref` from your `RowValueSet` method and see if it works, I can't see any reason to pass by reference. `DataGridViewRow` is already a reference type. — DaveShaw, Feb 11 '14 at 12:54
if I remove ref than how changes made to a row reflect the row of datagridview row. this is not possible @DaveShaw — Amit Bisht, Feb 11 '14 at 17:05
Have you tried it? Also, see this article by Jon Skeet on the topic: http://www.yoda.arachsys.com/csharp/parameters.html — DaveShaw, Feb 11 '14 at 17:23

score 2 · Accepted Answer · answered Feb 12 '14 at 14:06

you cannot assign an iterated, enumerated item using a "foreach" or even a "for". i got around that once, using that piece of code :

List<DataGridViewRow> lstDgr = new List<DataGridViewRow>();
foreach(DataGridViewRow dgr in dgvMarksEntryByClassWise.Rows)
{
   DataGridViewRow dgrTemp = dgr;
   RowValueSet(ref dgrTemp);
   lstDgr.Add(dgrTemp);
}  
dgvMarksEntryByClassWise.Rows.Clear();
dgvMarksEntryByClassWise.Rows.AddRange(lstDgr); //Not sure about the AddRange, try the Add method instead

Hope this helps

and btw, i wouldn't use a "Ref", instead i would pass a DataGridViewRow object in return to simply have : lstDgr.Add(RowValueSet(dgr)); — Sebastien H., Feb 12 '14 at 14:09

score 2 · Answer 2 · answered Feb 17 '14 at 18:03

As stated in the comments above, you do not need to pass DataGridViewRow by reference. Remove ref from the parameter.

void RowValueSet(DataGridViewRow dgr)
{
    dgr.Cells["StudentZero"].Value = ss.Where(w => w.MarksheetMarks == "0").Count();
    if (ss.Count() != 0)
        dgr.Cells["StudentISEmpty"].Value = Convert.ToInt16(lblTotlatStudent1.Text) - ss.Count();
    else
        dgr.Cells["StudentISEmpty"].Value = 0;
    dgr.Cells["StudentEntry"].Value = ss.Count();
}

If the values in the grid do not appear to be updating, it's for another reason. Do you re-bind the grid when you need to refresh the display?

score 1 · Answer 3 · answered Jan 21 '14 at 05:47

1

How about this ?

for (int i = 0; i < dgvMarksEntryByClassWise.Rows.Count; i++)
{
   var myRow = dgvMarksEntryByClassWise.Rows[i];
   RowValueSet(ref myRow);
}

answered Jan 21 '14 at 05:47

Selman Genç

100,147
13
119
184

sorry @Selman22 I pass it but still when i'm assigning value to cells of rows it is not assingning it to Datagridviewcells – Amit Bisht Jan 21 '14 at 05:51
it passed the row but value is not assigned to datagridview cell – Amit Bisht Jan 21 '14 at 05:54
then maybe the problem is in your RowValueSet method? are you sure it's correct? – Selman Genç Jan 21 '14 at 05:56
i am sure there in no problem with rowvalueset – Amit Bisht Jan 21 '14 at 06:05

Adam Valpied · Answer 4 · 2014-02-18T08:16:16.030

I agree with the comments about not passing the row using ref. It is a reference type. You generally only use that keyword with value types (such as int, etc).

I've had problems with the DataGridView not updating after changing cell values and often have needed to call dataGridView1.Invalidate(); It depends how things are hooked up. If you use data-binding with a class that inherits from INotifyPropertyChanged then it always seems to work, but if you just change cell values I have noticed the odd time that it would not update.

Here is an example that works. Create a new app, add an empty DataGridView onto the form and replace the code with the following. This proves that you do not need to use ref.

 public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();

            dataGridView1.Columns.Add(new DataGridViewTextBoxColumn() { Name = "Column1" });
            dataGridView1.Columns.Add(new DataGridViewTextBoxColumn() { Name = "Column2" });
            dataGridView1.Columns.Add(new DataGridViewTextBoxColumn() { Name = "Column3" });
            dataGridView1.Columns.Add(new DataGridViewTextBoxColumn() { Name = "Column4" });

            for (int i = 0; i <= 4; i++)
            {
                dataGridView1.Rows.Add();
            }

            foreach (DataGridViewRow row in dataGridView1.Rows)
            {
                RowValueSet(row);
            }
        }

        private void RowValueSet(DataGridViewRow row)
        {
            row.Cells["Column1"].Value = "1";
            row.Cells["Column2"].Value = "2";
            row.Cells["Column3"].Value = "3";
            row.Cells["Column4"].Value = "4";
        }
    }

I imagine that your problem lies elsewhere

Passing DataGridViewRow as referance

Update Code

4 Answers4