Accessing session through pagemethods throw webServiceError when connecting to SQL Server

Question

I have a problem with accessing values in the session through pagemethods when I try connecting to SQL Server.

I have uploadEngin.aspx page for uploading files and for monitoring the upload state I store the state value (like 10%) in session. In the uploadEngin.aspx page I am connecting to SQL Server to get the valid extension for files. I have a basic problem. Example below show a 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) everything works fine and I see the "hello" message. When I use that code however (connecting to SQL Server to get the valid extension), I get

WebServiceError: Object reference not set to an instance of an object

How should I solve this problem?

add attribute `[WebMethod(EnableSession = true)]` on your webmethod — techspider, Aug 08 '16 at 20:51
I don't understand why you have three different `g()` functions? — techspider, Aug 08 '16 at 20:58
Where are you getting error now? What is your error? Did you put a breakpoint at `return HttpContext.Current.Session["s"].ToString();` and evaluate the expression? — techspider, Aug 08 '16 at 21:03
in javascript code "console.log(r);" was fired,and i get this "Object reference not set to an instance of an object" in console,normaly i should get "hello" message — siamak, Aug 08 '16 at 21:09
change it to `alert(r)` and see; are you able to do debug and evaluate `return HttpContext.Current.Session["s"].ToString()`? — techspider, Aug 08 '16 at 21:09
what is count? you are hard coding `this.Session["s"] = "hello";` I'm not sure where you are heading to!! — techspider, Aug 08 '16 at 21:15
It is absolutely difficult to solve multiple problems with a single question; You need to be able to provide a scenario and start breaking your problems, working with one at a time posting a separate question for each unique problem — techspider, Aug 08 '16 at 21:16
You can refer [this question](http://stackoverflow.com/questions/16775117/asp-net-scriptmanager-pagemethods-is-undefined) which has multiple answers on how to use Javascript to call WebMethods — techspider, Aug 08 '16 at 21:17
i just have one problem,when i use "GetExtentionAndMainPath" i lose my session — siamak, Aug 08 '16 at 21:21

score 0 · Answer 1 · answered Aug 08 '16 at 20:55

0

You need to set EnableSession property on your WebMethod attribute in order to access Session values in your web method.

[WebMethod(EnableSession = true)]
public static String g()
{
    return HttpContext.Current.Session["s"].ToString();
}

For more details, please refer the MSDN link.

answered Aug 08 '16 at 20:55

techspider

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thank you for Answering,i add (EnableSession = true),but still i get that error – siamak Aug 08 '16 at 20:59

Accessing session through pagemethods throw webServiceError when connecting to SQL Server

1 Answers1