private DataTable table;

public void Build()
        {
            table = new DataTable();
            table.Columns.Add("id");
            table.Columns.Add("first_name");
            table.Columns.Add("last_name");
            table.Columns.Add("contact");
            table.Columns.Add("address");
            table.Columns.Add("gender");

            dataGridView1.DataSource = table;
        }
private void dataGridView1_CellMouseClick(object sender, DataGridViewCellMouseEventArgs e)
        {
            int rowIndex = e.RowIndex;
            label6.Text = dataGridView1.Rows[rowIndex].Cells[0].Value.ToString();
        }    
private void button2_Click(object sender, EventArgs e)
        {
            var row = (dataGridView1.CurrentRow.DataBoundItem as DataRowView).Row;
            var form = new Form2();
            form.Build(row);
            form.ShowDialog();

            DataTable dt = dal.Select();
            dataGridView1.DataSource = dt;
        }

public DataRow Data { get; private set; }

        public void Build(DataRow data)
        {
            Data = data;//сохрняем объект в своем свойстве

            label6.Text = Data["id"].ToString();
            textBox1.Text = Data["first_name"].ToString();
            textBox2.Text = Data["last_name"].ToString();
            textBox3.Text = Data["contact"].ToString();
            textBox4.Text = Data["address"].ToString();
            textBox5.Text = Data["gender"].ToString();
        }