How do I make null rows invisible

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Hello everyone,
I am making a c# winform application using an sql database which i bound to my datagridview.After I loaded the collumns I needed, there are rows where I put a null value, and I'd like to remove those each time the cell value in one of my loaded columns is null. Can anyone help me?
The code down below is what I tried so far, but there seems to be an error.

What I have tried:

C#

<pre>private void comboBox2_SelectedIndexChanged(object sender, EventArgs e)
        {
            dataGridView2.Columns.OfType<DataGridViewColumn>().ToList().ForEach(col => col.Visible = false);

            dataGridView2.Columns["lotDataGridViewTextBoxColumn"].Visible = true;
            dataGridView2.Columns["ItemDataGridViewTextBoxColumn"].Visible = true;
            dataGridView2.Columns[$"{comboBox1.Text+comboBox2.Text}DataGridViewTextBoxColumn"].Visible = true;
foreach (DataGridViewRow row in dataGridView2.Rows)
            {
                if(dataGridView2.Rows[row.Index].Cells[$"{comboBox1.Text + comboBox2.Text}DataGridViewTextBoxColumn"].Value?.ToString() is null)
                {
                    CurrencyManager currencyManager1 = (CurrencyManager)BindingContext[dataGridView2.DataSource];
                    currencyManager1.SuspendBinding();
                    currencyManager1.ResumeBinding();

                }
            }
            



        }

Posted 15-Jun-23 0:02am

LiterallyGutsFromBerserk

Updated 15-Jun-23 2:37am

v2

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Graeme_Grant 15-Jun-23 6:11am

Best solution is in your SQL query, ensure no null rows are returned.

LiterallyGutsFromBerserk 15-Jun-23 6:13am

I don't know how to do that, since I bound my database in the winform datagridview task menu. How do I access the query from there?

here is the code btw: this.toleranceTableAdapter1.Fill(this.dataSet2.Tolerance);

Richard MacCutchan 15-Jun-23 6:14am

"there seems to be an error."
And exactly what error would that be?

LiterallyGutsFromBerserk 15-Jun-23 6:18am

Unable to make uncommitted newline invisible.

Richard MacCutchan 15-Jun-23 6:20am

And where is that happening? You need to use the debugger to trace which line of code is doing this. It sounds like there is a disconnect between the DataGridView and its BindingSource.

LiterallyGutsFromBerserk 15-Jun-23 6:22am

it's happening between both Currency manager methods i called

Richard MacCutchan 15-Jun-23 6:33am

It looks like you are binding to the DataGridView, instead of the actual data source, so you are trying to modify data at the wrong point. NB, this is something of a guess as I am not expert at data binding.

LiterallyGutsFromBerserk 15-Jun-23 6:37am

Thank you for your input.I've come up with the same conclusion ,but have no idea how to solve that without modifying the code(I have to keep the datagridview).

Richard MacCutchan 15-Jun-23 7:00am

As far as I know, you should commit any changes you make to the DataGridView before you change any items that are waiting to be saved. As I said, I am not an expert in data binding, so I would suggest you check the documentation for guidance on the correct sequence of operations.

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OriginalGriff · Answer 1 · 2023-06-15T01:11:00

Solution 1

You cannot call ToString (or any other method) on a null value, and any call to ToString (other than the static Convert.ToString) method will always return at the very least an empty string: no successful call to object.ToString will ever return a null value.
So this code:

if(dataGridView2.Rows[row.Index].Cells[$"{comboBox1.Text + comboBox2.Text}DataGridViewTextBoxColumn"].Value?.ToString() is null)

Will never evaluate to true: it may throw a null reference exception though.

As Graeme has said, the best solution is to exclude the null value rows from your database access via the SQL query you load your DataAdapter / DataSet from.

Posted 15-Jun-23 1:11am

OriginalGriff

Comments

Richard Deeming 15-Jun-23 7:17am

Did you miss the null-conditional operator in that call?

(row).Value?.ToString() is null

If Value is null, the ToString method will not be called, and the expression will evaluate to null.

Of course, it would be simpler to write (row).Value is null instead. :)

LiterallyGutsFromBerserk 15-Jun-23 7:23am

Thank you for your reply. I found a solution thanks to your explanation, which is to turn my "null" cells into an empty string.

OriginalGriff 15-Jun-23 7:38am

A better solution is to change the SELECT query - then you don't have to faff about at all ...

LiterallyGutsFromBerserk · Answer 2 · 2023-06-15T02:37:00

Solution 2

After a bit of working on my code, I found a simple solution. If your datatable data window show you NULL, it's not the c# null, but rather an equivalent to "" in c#.

Therefore, in order to remove all "null" columns, you simply need to write :

if(dataGridView2.Rows[row.Index].Cells[$"{comboBox1.Text + comboBox2.Text}DataGridViewTextBoxColumn"].Value?.ToString() is null)

Thank you for the explanation Richard and OriginalGriff.

Posted 15-Jun-23 2:37am

LiterallyGutsFromBerserk

Comments

CHill60 15-Jun-23 8:58am

It would still be better to change the SELECT query so that those rows are not loaded in the first place. Add to your query

WHERE ColumnName IS NOT NULL

PIEBALDconsult 15-Jun-23 9:24am

Please don't try to answer your own question. Just use the Improve Question button to add it there.