private void dgvDados_CellContentDoubleClick(object sender, DataGridViewCellEventArgs e)
        {
            foreach (Form openForm in Application.OpenForms)
            {
                if (openForm is FrmEmprestimo)
                {
                    openForm.Close();
                }
            }
            int ID_Emprestimo = int.Parse(dgvDados.CurrentRow.Cells[0].Value.ToString());
            int ID_Usuario    = int.Parse(dgvDados.CurrentRow.Cells[1].Value.ToString());

            FrmEmprestimo frmEmprestimo = new FrmEmprestimo(ID_Usuario, ID_Emprestimo);

            frmEmprestimo.MdiParent = MdiParent;
            frmEmprestimo.Show();
        }
        private void btnEmprestimo_Click(object sender, System.EventArgs e)
        {
            bool found = false;

            foreach (Form openForm in Application.OpenForms)
            {
                if (openForm is FrmEmprestimo)
                {
                    openForm.Focus();
                    found = true;
                }
            }
            if (!found)
            {
                FrmEmprestimo frmEmprestimo = new FrmEmprestimo(login.ID);
                frmEmprestimo.MdiParent = this;
                frmEmprestimo.Show();
            }
        }