In winforms, I try to merge cell using cell border style.
There are some problem in cell border color.

attached file is screen shot.
plz help me

        private void BtnDel_Click(object sender, EventArgs e)
        {
            MergeCell(GvMain, new int[] { 1, 2, 3, 4, 5 });
        }

        private void MergeCell(RadGridView gv, int [] idx)
        {
            GridViewRowInfo Prev = null;
           
            foreach (GridViewRowInfo item in gv.Rows)
            {
                if (Prev != null)
                {
                    string s1 = string.Empty;
                    string s2 = string.Empty;

                    foreach (int i in idx)
                    {
                        GridViewCellInfo c1 = Prev.Cells[i];
                        GridViewCellInfo c2 = item.Cells[i];

                        //s1 += "|" + (c1 != null && c1.Value != null ? c1.Value.ToString() : string.Empty);
                        //s2 += "|" + (c2 != null && c2.Value != null ? c2.Value.ToString() : string.Empty);
                        s1 = (c1 != null && c1.Value != null ? c1.Value.ToString() : string.Empty);
                        s2 = (c2 != null && c2.Value != null ? c2.Value.ToString() : string.Empty);

                        if (s1 == s2)
                        {
                            //c2.Value = string.Empty;
                            c2.Style.ForeColor = Color.Transparent;

                            //c2.Style.DrawBorder = true;
                            c2.Style.CustomizeBorder = true;
                            c2.Style.BorderTopWidth = 0;
                            //c2.Style.BorderTopColor = Color.Transparent;
                        }
                        else
                        {
                            //c2.Style.CustomizeBorder = false;
                            Prev = item;

                            break;
                        }
                    }
                }
                else
                {
                    Prev = item;
                }
            }
        }