A页面有TextBox,并有方法public void upDatexsy(string x)
        {
             this.xsy.Text = x;
             this.xf.Focus();
            
        }

B页面执行按键事件,并调用A页面中的方法更新A页面中的TextBox

 private void xsyGridView1_KeyPress(object sender, KeyPressEventArgs e)
        {
            if (e.KeyChar.ToString() == "\r")
            {
                
                 string x = xsyGridView1.Rows[xsyGridView1.CurrentRow.Index - 1].Cells["aa"].Value.ToString();
                 MessageBox.Show(x);
                 PosMain.GetInstance().upDatexsy(x);
                this.Hide();
            }
        }

A页面中的TextBox始终无法赋值且xf无法得到焦点，请大神指点~！