Hi, I'm a student, weak programming. I ask for your help, I write a program in C #, there are two tables, but I do not understand how to organize the connection between them many to many. Table in DataGridView1 from DataSet1 on Form1 key connection in DataGridView1 from DataSet1 to Form3

I do this on Form1

private void dataGridView1_CellDoubleClick(object sender, DataGridViewCellEventArgs e) 
{
  if (e.RowIndex >= 0)
  {
    DataGridViewRow row = this.dataGridView1.Rows[e.RowIndex];
    Form1.IDfor3form = row.Cells[1].Value.ToString(); // By the Bilet column
    Form3 c = new Form3()