asp.net - Accessing session through pagemethods throw webServiceError when connecting to SQL Server -

i have problem accessing values in session through pagemethods when try connecting sql server.

i have uploadengin.aspx page uploading files , monitoring upload state store state value (like 10%) in session. in uploadengin.aspx page connecting sql server valid extension files. have basic problem. example below show sample code:

uploadengin:

protected void page_load(object sender, eventargs e) {     this.session["s"] = "hello";      if (!ispostback)     {         admin.app.core.attachment.attachmenttype att = new app.core.attachment.attachmenttype();         att.getextentionandmainpath("image");     } }  [system.web.services.webmethod(enablesession = true)] public static string g() {     return httpcontext.current.session["s"].tostring(); } 

javascript:

(function () {     window.onload = function () {         pagemethods.g(function (r) { alert(r); }, function (r) {             console.log(r);         });     } })(); 

getextentionandmainpath:

public string[] getextentionandmainpath(string name) {     string[] ext =new string[2];     string x = name;     uint64 id = findidbyname(x);      datatable dt = new dataaccess().executeselect("select_ano_attachmenttype", commandtype.storedprocedure, new dataparam("@id", id, sqldbtype.bigint));      if (dt.rows.count > 0)     {         ext[0] = dt.rows[0]["attachmenttype_validextention"].tostring();         ext[1]= dt.rows[0]["attachmenttype_mainpath"].tostring();     }      return ext; } 

without code inside if(!ispostback) works fine , see "hello" message. when use code (connecting sql server valid extension),

webserviceerror: object reference not set instance of object

how should solve problem?

you need set enablesession property on webmethod attribute in order access session values in web method.

[webmethod(enablesession = true)] public static string g() {     return httpcontext.current.session["s"].tostring(); } 

for more details, please refer msdn link.