public partial class EmployersAdd : Form
    {
        DataRow dr;
        public EmployersAdd()
        {
            InitializeComponent();
        }

        public EmployersAdd(DataRow _dr)
        {
            InitializeComponent();
            dr = _dr;
            dr.BeginEdit();
            FIO.Text = dr["FIO"].ToString();
            phoneMob.Text = dr["phone_mobile"].ToString();
        }

        private void Ok_Click(object sender, EventArgs e)
        {
            //employeeDataSet.employee.Rows.Add(dr);
            dr["FIO"] = FIO.Text;
            dr["phone_mobile"] = phoneMob.Text;
            dr.EndEdit();
            //dr.AcceptChanges();
            this.Close();
        }

    public partial class EmployersMain : Form
    {
        DataRow dr;
        private void bAdd_Click(object sender, EventArgs e)
        {
            dr = employeeDataSet.employee.NewRow();
            EmployersAdd child = new EmployersAdd(dr);
            child.ShowDialog();
            employeeDataSet.employee.Rows.Add(dr);
            employeeDataSet.AcceptChanges();
            employeeTableAdapter.Update(this.employeeDataSet.employee);
        }
...
        private void bFind_Click(object sender, EventArgs e)
        {
            this.employeeTableAdapter.Fill(this.employeeDataSet.employee);
            this.listEmployeers.DataSource = this.employeeBindingSource;
            this.listEmployeers.DisplayMember = "FIO";
            this.listEmployeers.ValueMember = "employee_id";
        }