private void BtnNew_Click(object sender, EventArgs e)
{
//I'm passing the Mainform (itself) as a parentises
DetailForm detailForm = new DetailForm(this);
detailForm.ShowDialog();
}
private void DataGridViewBook_CellContentClick(object sender, DataGridViewCellEventArgs e)
{
//Pass a parameters the book's ID and this form
DetailForm detailForm = new DetailForm(Convert.ToInt32(this.dataGridViewBook.CurrentRow.Cells[0].Value.ToString()), this);
detailForm.ShowDialog();
}