Question

I am a beginner in c#, I have two forms mainForm and subForm. The mainForm has DataGridView1 and the subForm has richTextBox1.

I want to add rows and columns to DataGridView1 from subForm through FormClosingEvent

I made the DataGridView1 modifier to public . It is showing in intellisense of subForm but maybe I am doing something wrong.

I have tried the below code in my subForm FormClosingEvent but I cant see any update to my DataGridView1.

   if (richTextBox1.Text != "")
        {
            mainForm newMainForm = new mainForm();
            newMainForm.dataGridView1.ColumnCount = 3;
            newMainForm.dataGridView1.Columns[0].Name = "Product ID";
            newMainForm.dataGridView1.Columns[1].Name = "Product Name";
            newMainForm.dataGridView1.Columns[2].Name = "Product Price";

            string[] row = new string[] { "1", "Product 1", "1000" };
            newMainForm.dataGridView1.Rows.Add(row);
            row = new string[] { "2", "Product 2", "2000" };
            newMainForm.dataGridView1.Rows.Add(row);
            row = new string[] { "3", "Product 3", "3000" };
            newMainForm.dataGridView1.Rows.Add(row);
            row = new string[] { "4", "Product 4", "4000" };
            newMainForm.dataGridView1.Rows.Add(row);               
        }

Thanks in advance

Answer 1

So assuming your mainForm opens your subForm:

subForm sub = new SubForm();
sub.Show(); // or however you have done it

In your example, you need the subForm to be able to change something on the mainform, so, create a Public/Internal method on the subForm, similar to this:

private mainForm _parent;

internal void RegisterParent(mainForm form)
{
    // error handling of course, make sure form is not null, or you don't already have a parent
    this._parent = form;
}

In the mainform, after subForm.Show(), add something like:

sub.RegisterParent(this);

Now your subForm can manipulate the correct mainform instance:

if (richTextBox1.Text != "")
    {
        _parent.dataGridView1.ColumnCount = 3;
        _parent.dataGridView1.Columns[0].Name = "Product ID";
        _parent.dataGridView1.Columns[1].Name = "Product Name";
        _parent.dataGridView1.Columns[2].Name = "Product Price";

        string[] row = new string[] { "1", "Product 1", "1000" };
        _parent.dataGridView1.Rows.Add(row);
        row = new string[] { "2", "Product 2", "2000" };
        _parent.dataGridView1.Rows.Add(row);
        row = new string[] { "3", "Product 3", "3000" };
        _parent.dataGridView1.Rows.Add(row);
        row = new string[] { "4", "Product 4", "4000" };
        _parent.dataGridView1.Rows.Add(row);               
    }

I hope that helps!