I was looking this:
try
{
for (int i = 0; i < dataGridView1.RowCount; i++)
{
if (dataGridView1.Rows[i].Cells[0].Value.ToString() == txt_FName.Text)
{
dataGridView1.Rows[i].Cells[2].Value = [any proccess] ;
return;
}
}
}
catch(Exception ex)
{
MessageBox.Show(ex.Message);
}
dataGridView1.Rows.Add(txt_FName.Text, txt_LName.Text, txt_Number.Text);