Please help me to sort out this issue

Hi! I have following code and i need to set order by according to 'ToolNoFirstPart,ToolNoSecondPart'. how i can do that? please help

var oSearchRows = oStockDs.Tables[0].AsEnumerable() .Select(rt => {

                        CMS.DocumentEngine.TreeNode oNodeIn = GetNodeFromSearchResultsRow(rt["id"].ToString());

                        SKUInfo oSkuIn = SKUInfoProvider.GetSKUInfo(oNodeIn.NodeSKUID);

                        if (oSkuIn.SKUEnabled && !oNodeIn.GetBooleanValue("DocumentMenuItemHideInNavigation", true))
                        {
                            return rt;
                        }
                        else
                        {
                            return null;
                        }
                    }
                ).OrderBy(ord => {
                    CMS.DocumentEngine.TreeNode oNodeInfo = GetNodeFromSearchResultsRow(ord["id"].ToString());
                    SKUInfo oSkuInfo = SKUInfoProvider.GetSKUInfo(oNodeInfo.NodeSKUID);
                    string ToolNoFirstPart = "";
                    string ToolNoSecondPart = "";

                    if (oSkuInfo != null)
                    {
                        string ToolNo = ValidationHelper.GetString(oSkuInfo["skuNumber"], "");


                        string[] splitToolNo = ToolNo.Split(' ');
                        if (splitToolNo.Length > 0)
                        {
                            ToolNoFirstPart = splitToolNo[0];
                            ToolNoSecondPart = splitToolNo[1];
                        }
                    }
                    return "";
                }   
                ).OfType<DataRow>();

                //DataTable oDataTable = oSearchRows.Where(rt => (rt != null)).CopyToDataTable(); 
                DataTable oDataTable = oSearchRows.CopyToDataTable();