WebConfigurationManager.OpenWebConfiguration("~");
... .Save();

You are using a PopupControlExtender from the AjaxControlToolkit and you added a Button or an ImageButton in it and every time you click on it this ugly js error appears: this._postBackSettings.async is null or not an object. You Google and you see that the solution is to use a LinkButton instead of a Button or an ImageButton.

Well, I want my ImageButton! Therefore I added to the Page_Load method of my page or control this little piece of code to fix the bug:

private void FixPopupFormSubmit()
{
  var script =
    @"if( window.Sys && Sys.WebForms 
    && Sys.WebForms.PageRequestManager 
	&& Sys.WebForms.PageRequestManager.getInstance) {
  var prm = Sys.WebForms.PageRequestManager.getInstance();
  if (prm && !prm._postBackSettings) {
    prm._postBackSettings = prm._createPostBackSettings(false, null, null);
  }
}";
  ScriptManager.RegisterOnSubmitStatement(
    Page, 
    Page.GetType(), 
    "FixPopupFormSubmit", 
    script);
}

Hope it helps you all.

if (typeof (Sys) !== 'undefined') Sys.Application.notifyScriptLoaded();

    <asp:ScriptManagerProxy runat="server">
        <Scripts>
            <asp:ScriptReference Path="~/js/myScript.js" NotifyScriptLoaded="true" />
        </Scripts>
    </asp:ScriptManagerProxy>

if (HttpContext.Current.Session!=null) //do stuff with sessions

protected override void LoadViewState(object savedState)
    {
        base.LoadViewState(savedState);
        CreateControl(ControlName);
    }

• set the ReportViewer AsyncRendering property to false - doesn't work
• use the IP address instead of the server name, because the ReportViewer has issues with the underline character - doesn't work, albeit, I didn't have any underline characters in my server name to begin with
• set the maximum workers from 2 to 1 in the web.config (not tried, sounds dumb)
• setting cookieless to true in the web.config sessionState element - it horribly changed my URL, and it worked, but I would never use that
• setting ProcessingMode to local - that seemed to work, but then it stopped working, although I am not using the ReportViewer with a Reporting Services server
• Because towards the end I've noticed that the problem was not an expiration, but more of a Session communication problem, I tried setting machineKey in web.config, although it doesn't work for the InProc setting. So it didn't work either.

• the error message looks like this:

  ASP.NET session has expired
  Stack Trace: 
  [AspNetSessionExpiredException: ASP.NET session has expired]
     Microsoft.Reporting.WebForms.ReportDataOperation..ctor() +556
     Microsoft.Reporting.WebForms.HttpHandler.GetHandler(String operationType) +242
     Microsoft.Reporting.WebForms.HttpHandler.ProcessRequest(HttpContext context) +56
     System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +181
     System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +75

• the error occurs in the constructor of ReportDataOperation:

  public ReportDataOperation():
  this.m_instanceID = 
     HandlerOperation.GetAndEnsureParam(requestParameters, "ControlID");
  this.m_reportHierarchy = 
     (ReportHierarchy) HttpContext.Current.Session[this.m_instanceID];
  if (this.m_reportHierarchy == null)
     throw new AspNetSessionExpiredException();
  

• the Session object that makes the error be thrown is set in the SaveViewState() override method in ReportViewer
• Apparently, the error occurs only sometimes (probably after the HttpApplication was restarted and during the debug mode of Visual Studio).

1. the ReportViewer control was poorly designed
2. the ASP.Net Session expired error is misdirecting the developer, since it is not an expiration problem
3. the actual problem lies in the inability of the ReportViewer control to communicate with the HttpHandler.
4. The problem also could be related to the browser using separate threads to get the application and access the HttpHandler.

var somethings=from something in db.Somethings....;
var data = somethings.OrderBy(Sort + " asc");
gv.DataSource=data;
gv.DataBind();

// Get the text/value for the item
try {
var pair = Sys.Serialization.JavaScriptSerializer.deserialize('(' + completionItems[i] + ')');
if (pair && pair.First) {
// Use the text and value pair returned from the web service
text = pair.First;
value = pair.Second;
} else {
// If the web service only returned a regular string, use it for
// both the text and the value
text = pair;
value = pair; 
} 
} catch (ex) {
text = completionItems[i];
value = completionItems[i];
}

using System;
using System.IO;
using System.Web.UI;
using System.Web.UI.WebControls;
using AjaxControlToolkit;

namespace Siderite.Web.WebControls
{
    /// <summary>
    /// AutoCompleteExtender with templating
    /// </summary>
    public class AdvancedAutoComplete : AutoCompleteExtender, INamingContainer
    {
        private ITemplate _template;

        [TemplateContainer(typeof(Content))]
        [PersistenceMode(PersistenceMode.InnerProperty)]
        public ITemplate ItemTemplate
        {
            get { return _template; }
            set { _template = value; }
        }

        protected override void OnInit(EventArgs e)
        {
            base.OnInit(e);
            const string script = @"
function AdvancedItemDisplay(behaviour,args) {
    var template=behaviour.get_element().getAttribute('_template');
    //if (!template==null) template='${0}';
    for (var i=0; i<behaviour._completionListElement.childNodes.length; i++) {
        var item=behaviour._completionListElement.childNodes[i];
        var vals = item._value;
        var html=template;
        for (var c=0; c<vals.length; c++)
            html=html.replace(new RegExp('\\$\\{'+c+'\\}','g'),vals[c]);
        item.innerHTML=html;
    }
}

function AdvancedSetText(behaviour,args) {
        var vals=args._value;
        var element=behaviour.get_element();
        var control = element.control;
        if (control && control.set_text)
            control.set_text(vals[0]);
        else
            element.value = vals[0];
    }
";
            ScriptManager.RegisterClientScriptBlock(this, GetType(), "AdvancedAutoComplete", script, true);

            OnClientShowing = "AdvancedItemDisplay";
            OnClientItemSelected = "AdvancedSetText";
        }

        protected override void OnPreRender(EventArgs e)
        {
            base.OnPreRender(e);
            string template = GetTemplate();
            ((TextBox)TargetControl).Attributes["_template"] = template;
        }

        private string GetTemplate()
        {
            Content ph=new Content();
            ph.Page = Page;
            _template.InstantiateIn(ph);
            HtmlTextWriter htw = new HtmlTextWriter(new StringWriter());
            ph.RenderControl(htw);
            return htw.InnerWriter.ToString();
        }
    }
}

using System.Collections.Generic;
using System.Web.Script.Serialization;
using System.Web.Script.Services;
using System.Web.Services;

/// <summary>
/// Web service to send auto complete items to the AdvancedAutoComplete extender
/// </summary>
[WebService(Namespace = "http://tempuri.org/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
[ScriptService]
public class MainService : WebService
{
    [WebMethod]
    [ScriptMethod]
    public string[] GetCompletionList(string prefixText, int count)
    {
        JavaScriptSerializer jss=new JavaScriptSerializer();
        List<string> list=new List<string>();
        for (int c = 0; (list.Count< count) && (c < 100000); c++)
        {
            string s = (c*c).ToString();
            if (s.StartsWith(prefixText))
            {
                object[] item = new object[] {s, "images/demo.gif"};
                list.Add(jss.Serialize(item));
            }
        }
        return list.ToArray();
    }
}

<asp:TextBox runat="server" ID="tbMain"></asp:TextBox>
<cc1:AdvancedAutoComplete ID="aceMain" runat="server" BehaviorID="mhMain" TargetControlID="tbMain"
    ServiceMethod="GetCompletionList" ServicePath="~/MainService.asmx" MinimumPrefixLength="0"
    CompletionInterval="0">
    <ItemTemplate>
        <asp:Image runat="server" ID="imgTest" ImageUrl="${1}" /><asp:Label runat="server"
        ID="lbTest" Text="${0}"></asp:Label>
    </ItemTemplate>
</cc1:AdvancedAutoComplete>

var fu = ie.FileUpload(Find.ByName("ctl00$ContentPlaceHolder1$tcContent$tpAddItem$uplGalleryItem$fuGalleryItem"));
fu.Set(UploadImageFile);