Adding datatable into dataset is allways empty althout datatable has rows

protected void showMembers(Boolean filtered=false)
      {
          using (var cn = GetConnection())
          {
              cn.Open();
              string cmsGetProfiles = "SELECT * FROM [Vm_siteMembers] order by [Last Login Time] desc ";

              SqlDataAdapter EventsAdapter = new SqlDataAdapter(cmsGetProfiles, cn);
              BaseMembersListDS.Clear();// this DataSet defined as public static

              EventsAdapter.Fill(BaseMembersListDS);

              using (DataSet filteredMemberListDS = new DataSet())
              {
                  filteredMemberListDS.Merge(BaseMembersListDS.Tables[0]);
                  if (filtered)
                  {
                      DataTable dt = new DataTable(); dt.TableName = "filtered";

                      filteredMemberListDS.Clear();
                      foreach (var item in BaseMembersListDS.Tables[0].Columns)
                          dt.Columns.Add(item.ToString());

                      foreach (DataRow dr in BaseMembersListDS.Tables[0].AsEnumerable().Take(5))
                          dt.ImportRow(dr);

                      filteredMemberListDS.Tables.Add(dt);
                  }
                  MembersdataBind(filteredMemberListDS);//why filteredMemberListDS is empty
              }
          }
      }

      protected void MembersdataBind(DataSet filteredMemberList)
      {

          MemebersDdl.DataSource = filteredMemberList;
          MemebersDdl.DataBind();
      }

Columns headers on datatable match by doing this

foreach (var item in BaseMembersListDS.Tables[0].Columns)
                            dt.Columns.Add(item.ToString());