js 弹窗，模态跳转非模态窗口，丢失session

A页面打开B页面模态窗口

function TargetCost() {
            var strprojGUID = getQueryStringByName("ProjGUID");
            var sFile = "/Tzsy/SelectVersion.aspx?ProjGUID=" + strprojGUID + "&CompilerGUID=" + getQueryStringByName("CompilerGUID");
//            openMyDlg("选择编制目标版本", sFile, '', '', 350, 170);

            window.showModalDialog(sFile, window, "dialogWidth=350px;dialogHeight=170px");    
            
        }

B模态窗口页面 打开非模态窗口页C

  var   sFile = "/Cbgl/ProjectTargetStage_Grid.aspx?ProjectGUID=" + strProjGUID + "&SetVersion=&IsPlan=1&ProjectTargetStage=" + TargetStage2ProjectGUID + "&StageName=" + strStageName + "&CompilerGUID=" + strCompilerGUID;
 
 var topwindow = window.dialogArguments;
       topwindow.open(sFile)