(C#.Net) Windows Application - DataGridView Up or Down Button

private int pos = 0;

protected override bool ProcessCmdKey(ref Message msg, Keys keyData)
{
            if ((keyData == (Keys.Up)) || (keyData == (Keys.Down)))
            {
                int rowIndex = dg_name.CurrentCell.RowIndex;
                if (keyData == (Keys.Up))
                {
                    upDataGridViewRow();
                    //return true;
                }
                if (keyData == (Keys.Down))
                {
                    downDataGridViewRow();
                    //return true;
                }
            }
            return base.ProcessCmdKey(ref msg, keyData);
}

private void upDataGridViewRow()
{
            try
            {
                pos = dg_name.BindingContext[dtSet, "cus"].Position - 1;

                if (pos < 0)
                    return;
                else
                {
                    dg_name.BindingContext[dtSet, "cus"].Position -= 1;

                    dg_name.Rows[rowIndex].Selected = false;
                    dg_name.Rows[dg_name.BindingContext[dtSet, "cus"].Position].Selected = true;
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
}

private void downDataGridViewRow()
{
            try
            {
                pos = dg_name.BindingContext[dtSet, "cus"].Position + 1;
                int numRows = dtSet.Tables["cus"].Rows.Count;

                if (pos == (numRows))
                    return;
                else
                {
                    dg_name.BindingContext[dtSet, "cus"].Position += 1;

                    dg_name.Rows[rowIndex].Selected = false;
                    dg_name.Rows[dg_name.BindingContext[dtSet, "cus"].Position].Selected = true;
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
}

            DataTable dt = new DataTable("Test");
            DataColumn dc1 = new DataColumn("TestID");
            DataColumn dc2 = new DataColumn("TestName");

            dt.Columns.Add(dc1);
            dt.Columns.Add(dc2);

            DataRow dr = dt.NewRow();
            dr.SetField("TestID", "R1");
            dr.SetField("TestName", "RowsName1");
            dt.Rows.Add(dr);

            DataRow dr1 = dt.NewRow();
            dr1.SetField("TestID", "R2");
            dr1.SetField("TestName", "RowsName2");
            dt.Rows.Add(dr1);

            BindingSource BS = new BindingSource();
            BS.DataSource = dt;

            BindingNavigator BN = new BindingNavigator(BS);
            

            TextBox txtID = new TextBox();
            TextBox txtName = new TextBox();
            txtID.Location = new Point(110, 50);
            txtName.Location = new Point(110, 80);

            this.Controls.Add(BN);
            this.Controls.Add(txtID);
            this.Controls.Add(txtName);

            txtID.DataBindings.Add("Text",BS, "TestID");
            txtName.DataBindings.Add("Text", BS, "TestName");

            DataTable dt = new DataTable("Test");
            DataTable dtdt = new DataTable("TestDetial");
            DataColumn dc1 = new DataColumn("TestID");
            DataColumn dc2 = new DataColumn("TestName");

            DataColumn dcdt1 = new DataColumn("DetialID");
            DataColumn dcdt2 = new DataColumn("DetialName");
            DataColumn dcdt3 = new DataColumn("TestID");


            dt.Columns.Add(dc1);
            dt.Columns.Add(dc2);

            dtdt.Columns.Add(dcdt1);
            dtdt.Columns.Add(dcdt2);
            dtdt.Columns.Add(dcdt3);

            DataRow dr = dt.NewRow();
            dr.SetField("TestID", "R1");
            dr.SetField("TestName", "RowsName1");
            dt.Rows.Add(dr);

            DataRow dr1 = dt.NewRow();
            dr1.SetField("TestID", "R2");
            dr1.SetField("TestName", "RowsName2");
            dt.Rows.Add(dr1);

            DataRow drdt1 = dtdt.NewRow();
            drdt1.SetField("DetialID", "S1");
            drdt1.SetField("DetialName", "Student1");
            drdt1.SetField("TestID", "R1");
            dtdt.Rows.Add(drdt1);

            DataRow drdt2 = dtdt.NewRow();
            drdt2.SetField("DetialID", "S2");
            drdt2.SetField("DetialName", "Student2");
            drdt2.SetField("TestID", "R1");
            dtdt.Rows.Add(drdt2);

            BindingSource BS = new BindingSource();
            BindingSource BSDetial = new BindingSource();
            BS.DataSource = dt;
          

            DataSet DS = new DataSet();
            DS.Tables.Add(dt);
            DS.Tables.Add(dtdt);


            DataRelation dtr = new DataRelation("TestRelation", DS.Tables["Test"].Columns["TestID"], DS.Tables["TestDetial"].Columns["TestID"],false);
            DS.Relations.Add(dtr);

            BSDetial.DataSource = BS;
            BSDetial.DataMember = "TestRelation";
       

            BindingNavigator BN = new BindingNavigator(BS);
            

            TextBox txtID = new TextBox();
            TextBox txtName = new TextBox();
            txtID.Location = new Point(110, 50);
            txtName.Location = new Point(110, 80);

            DataGridView dgv = new DataGridView();
            dgv.DataSource = BSDetial;
            dgv.Location = new Point(40, 110);

            this.Controls.Add(BN);
            this.Controls.Add(txtID);
            this.Controls.Add(txtName);
            this.Controls.Add(dgv);

            txtID.DataBindings.Add("Text",BS, "TestID");
            txtName.DataBindings.Add("Text", BS, "TestName");