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Object Reference Error. Pls Help!

 
 
fshort
Guest
Posts: n/a
 
      02-26-2006
Hi,
I'm having a major issue with one of the custom contols I've created.
Basically, it consists of a dropdown, button and some textboxes for the
user to enter values. When the user changes the item in the dropdown,
it posts back to change which textboxes appear within the control (i.e.
other textboxes will appear based on the selection in the dropdown).
The button is used to refresh the data in a grid based on the values
the user keyed into the textboxes in my control. I have 2 events wired
up for my custom control - the Click event for the button and the
SelectedIndexChanged event for the dropdown.

The general flow of the control processing is as follows: All the child
controls of the custom control are added dynamically at runtime. The
data used to build these controls are retrieved from a call to a soap
service from the Init method of the custom control. When the control
lifecycle gets to CreateChildControls, all the child controls are
created based on this data. This is where the dropdown, button and
textboxes are created and events wired up.

This control works properly 90% of the time. The problem I'm having is
that every once in a while when the user clicks the button, the
SelectedIndexChanged event of the dropdown fires event though it wasnt
changed. This is the error that occurs:

Object reference not set to an instance of an object.
at
System.Web.UI.WebControls.Button.System.Web.UI.IPo stBackEventHandler.RaisePostBackEvent(String
eventArgument)
at System.Web.UI.Page.RaisePostBackEvent(IPostBackEve ntHandler
sourceControl, String eventArgument)
at System.Web.UI.Page.RaisePostBackEvent(NameValueCol lection
postData)
at System.Web.UI.Page.ProcessRequestMain()

What makes this so difficult to solve is that I cannot reliably
reproduce the error. Seems to come and go. I've added my code and the
Trace output from the control execution (some code removed for
brevity). Any help or insight into this issue would be greatly
appreciated.

Thanks,
Fred

using System;
using System.Collections;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.HtmlControls;
using System.ComponentModel;
using System.Xml;
using System.IO;
using System.Web.Caching;
using System.Configuration;

namespace MyCntl.WebControls.WebControls {

public class ViewEditor : WebControl, INamingContainer {
private ArrayList _FilterControls = new ArrayList();

private DropDownList _ddlViews;
private Button _btnRefresh;
private string _selectedViewId;
private object _results = null;

protected static readonly object EventClick = new object();
protected static readonly object EventSelectedIndexChanged = new
object();

#region Control Properties

[
Category("Action"),
Description("Raised when the refresh button is clicked.")
]
public event EventHandler Refresh {
add {
Events.AddHandler(EventClick, value);
}
remove {
Events.RemoveHandler(EventClick, value);
}
}

[
Category("Action"),
Description("Raised when the selected view changes.")
]
public event EventHandler ViewChanged {
add {
Events.AddHandler(EventSelectedIndexChanged, value);
}
remove {
Events.RemoveHandler(EventSelectedIndexChanged, value);
}
}

/// <summary>
/// The ID of the currently seleced view.
/// </summary>
[
Category("Data"),
DefaultValue(""),
Description("Current selected view id."),
Browsable(false)
]
public string SelectedViewId {
get {
this.EnsureChildControls();
return this._ddlViews.SelectedValue;
}
}

/// <summary>
/// Unique key for storing the data provided by the soap service in
cache
/// </summary>
[
Category("Data"),
DefaultValue(""),
Description("Unique key for storing the data provided by the soap
service in cache."),
Browsable(false)
]
private string ControlKey {
get {
return Page.GetType().FullName + this.ID;
}
}

public override ControlCollection Controls {
get {
EnsureChildControls();
return base.Controls;
}
}
#endregion

#region Control Events
protected override void OnInit(EventArgs e) {
base.OnInit (e);
InitializeControlData(!Page.IsPostBack);
}

protected override void TrackViewState() {
base.TrackViewState();
}

protected override void LoadViewState(object savedState_) {
base.LoadViewState(savedState_);
}

protected override object SaveViewState() {
object viewState = base.SaveViewState();
return viewState;
}

protected override void OnLoad(EventArgs e) {
base.OnLoad (e);
}

/// <summary>
/// Click event delegate
/// </summary>
/// <param name="e"></param>
protected virtual void OnClick(EventArgs e) {
EventHandler handler = (EventHandler)Events[EventClick];
if (handler != null) {
handler(this, e);
}
}

/// <summary>
/// SelectedIndexChanged event delegate.
/// </summary>
/// <param name="e"></param>
protected virtual void OnSelectedIndexChanged(EventArgs e) {
EventHandler handler =
(EventHandler)Events[EventSelectedIndexChanged];
if (handler != null) {
handler(this, e);
}
}
#endregion

#region Event Handlers
private void _ddlViews_SelectedIndexChanged(object sender,
System.EventArgs e) {
InitializeControlData(true);
this.OnSelectedIndexChanged(e);
}

private void _btnRefresh_Click(object sender, EventArgs e) {
this.OnClick(e);
}
#endregion

#region Control Data
/// <summary>
/// Gets data needed for creating the control - either from data in
session or from a call to the service.
/// </summary>
/// <param name="reinitialize_"></param>
public void InitializeControlData(bool reinitialize_) {
try {
_results = Page.Session["VIEW_EDITOR_DATA"];
if (_results != null) {
XmlDocument doc = new XmlDocument();
doc.LoadXml((string)_results);
_results = doc.DocumentElement;
}

if (_results == null || reinitialize_) {
//first check the viewId that was posted from the views drop down
this._selectedViewId = Page.Request.Params[this.UniqueID + ":" +
"userViews"];
if (this._selectedViewId == null || this._selectedViewId.Length ==
0) {
//this view id comes in the url when clicking from summary to
list
this._selectedViewId = Page.Request.Params["viewId"];

}

_results = GetControlData();

if (_results != null) {
Page.Session.Add("VIEW_EDITOR_DATA",
((XmlElement)_results).OuterXml);
}

this.ChildControlsCreated = false;
}
} catch (Exception _e) {
System.Console.Writeln("");
}
}

/// <summary>
/// Makes call to soap service to retreive control data.
/// </summary>
/// <returns></returns>
private XmlElement GetControlData() {
XmlElement results = null;

try {
IntializeProxyConnection();
results = Proxy.GetViewEditorData(this.CurrentUser,
this.SubjectName, this.RepositoryName, this._selectedViewId);
} catch (Exception _e) {
throw _e;
}

return results;
}

/// <summary>
/// Sets the proxy URL and timeout based on config params.
/// </summary>
private void IntializeProxyConnection() {
if (this.DataServiceURLConfigParam.Length > 0) {

Proxy.ServiceURL =
(string)ConfigurationSettings.AppSettings[this.DataServiceURLConfigParam];
Proxy.ServiceTimeout =
Int32.Parse((string)ConfigurationSettings.AppSetti ngs[this.DataServiceTimeoutConfigParam]);
} else {
Proxy.ServiceURL = this.DataServiceURL;
Proxy.ServiceTimeout = this.DataServiceTimeout;
}
}
#endregion

#region Child Control Creation
/// <summary>
/// Calls to the individual methods to create the child controls
/// </summary>
protected override void CreateChildControls() {
Controls.Clear();
CreateViewsDropDown();
CreateFilterControls();
CreateRefreshButton();

}

/// <summary>
/// Creates the Views dropdown and populated based on the xml data
retrieved from the service.
/// Assigns an event handler for the selectedindexchanged event.
/// </summary>
private void CreateViewsDropDown() {
this._ddlViews = new DropDownList();
XmlNode _views = ((XmlElement)_results).SelectSingleNode("Views");
if (_views != null && _views.ChildNodes.Count > 0) {
foreach (XmlNode node in _views.ChildNodes) {
string viewId = node.Attributes["Id"].Value;
string viewName = node.Attributes["Name"].Value;
ListItem view = new ListItem(viewName, viewId);
if (node.Attributes["default"] != null) {
view.Selected = Boolean.Parse(node.Attributes["default"].Value);
}
_ddlViews.Items.Add(view);
}
}

_ddlViews.ID = "userViews";
_ddlViews.AutoPostBack = true;
_ddlViews.SelectedIndexChanged += new
EventHandler(this._ddlViews_SelectedIndexChanged);
_ddlViews.Attributes.Add("class", "inputtext");
_ddlViews.EnableViewState = true;
Controls.Add(_ddlViews);
}

/// <summary>
/// Creates the Refresh button and assigns the event handler for the
Click event.
/// </summary>
private void CreateRefreshButton() {
_btnRefresh = new Button();
_btnRefresh.ID = "btnRefresh";
_btnRefresh.CommandName = "Refresh";
_btnRefresh.Click += new EventHandler(_btnRefresh_Click);
_btnRefresh.Attributes.Add("class", "viewEditorButton");
_btnRefresh.Text = "Refresh";

Controls.Add(_btnRefresh);
}

/// <summary>
/// Calls individual methods to create the filter controls.
/// </summary>
private void CreateFilterControls() {

XmlNode Filters =
((XmlElement)_results).SelectSingleNode("Filters") ;
if (Filters != null) {
this._FilterControls = new ArrayList();
foreach (XmlNode qf in Filters) {
if (qf.Attributes["controlType"] != null) {
string controlTypeName = qf.Attributes["controlType"].Value;
switch(controlTypeName) {
case "DropDownInputControl":
CreateFilterDropDownControl(qf);

break;
case "DateInputContol":
CreateFilterDateControl(qf);

break;
default:
CreateFilterTextboxControl(qf);

break;
}
}
}
}

if (this._FilterControls.Count == 0) {
throw new Exception("No filters configured for view.");
}
}


private void CreateFilterTextboxControl(XmlNode qf_) {

FilterTextBox tbFilter = new FilterTextBox();
this._FilterControls.Add(tbFilter);
}


protected override void RenderContents(HtmlTextWriter output)
{
//render controls here
}
}
}


Request Details
Session Id: Request Type: POST
Time of Request: 2/15/2006 8:26:30 PM Status Code: 200
Request Encoding: Unicode (UTF- Response Encoding: Unicode (UTF-
Trace Information
Category Message From First(s) From Last(s)
aspx.page Begin Init
ViewEditor.OnInit() initializing control... 0.000058 0.000058
ViewEditor.InitializeControlData() Starting data retrieval 0.000088
0.000031
ViewEditor.SelectedViewId SelectedViewId set to
0xf0b00096ad7c0000010877db8fb6800c 0.000688 0.000600
ViewEditor.SelectedViewId SelectedViewId =
0xf0b00096ad7c0000010877db8fb6800c 0.000742 0.000054
ViewEditor.SelectedViewId SelectedViewId set to
0xf0b001b0928200000108b00caa00957b 0.000844 0.000102
ViewEditor.createQuickFilterControls Starting... 0.000871 0.000027
ViewEditor.CreateQuickFilterDropDownControl Starting 0.000924 0.000053
ViewEditor.CreateQuickFilterDropDownControl Done 0.002875 0.001951
ViewEditor.CreateQuickFilterDropDownControl Starting 0.002944 0.000069
ViewEditor.CreateQuickFilterDropDownControl Done 0.012737 0.009793
ViewEditor.createQuickFilterControls Done... 0.012803 0.000066
ViewEditor.InitializeControlData() data retrieval complete 0.012827
0.000024
ViewEditor.OnInit() init done 0.012850 0.000023
ViewEditor.TrackViewState() TrackViewState started 0.012874 0.000024
ViewEditor.TrackViewState() TrackViewState done 0.012897 0.000023
aspx.page End Init 0.013016 0.000119
aspx.page Begin LoadViewState 0.013045 0.000029
ViewEditor.LoadViewState() LoadViewState started 0.019257 0.006211
ViewEditor.LoadViewState() LoadViewState done 0.020940 0.001683
aspx.page End LoadViewState 0.021008 0.000068
aspx.page Begin ProcessPostData 0.021031 0.000023
ViewEditor.CreateChildControls Starting 0.024868 0.003837
ViewEditor.Controls Getting controls 0.024938 0.000070
ViewEditor.Controls Ensure child controls called. 0.024962 0.000024
ViewEditor.CreateGQViewsDropDown Starting 0.024986 0.000024
ViewEditor.SelectedViewId SelectedViewId set to
0xf0b001b0928200000108b00caa00957b 0.025098 0.000112
ViewEditor.Controls Getting controls 0.025165 0.000067
ViewEditor.Controls Ensure child controls called. 0.025188 0.000023
ViewEditor.CreateGQViewsDropDown Done 0.025214 0.000026
ViewEditor.Controls Getting controls 0.025274 0.000060
ViewEditor.Controls Ensure child controls called. 0.025298 0.000024
ViewEditor.Controls Getting controls 0.025645 0.000348
ViewEditor.Controls Ensure child controls called. 0.025712 0.000066
ViewEditor.Controls Getting controls 0.025737 0.000025
ViewEditor.Controls Ensure child controls called. 0.025769 0.000032
ViewEditor.Controls Getting controls 0.025803 0.000034
ViewEditor.Controls Ensure child controls called. 0.025826 0.000023
ViewEditor.CreateRefreshButton Starting 0.025850 0.000024
ViewEditor.Controls Getting controls 0.025879 0.000029
ViewEditor.Controls Ensure child controls called. 0.025902 0.000023
ViewEditor.CreateRefreshButton done 0.025927 0.000025
ViewEditor.Controls Getting controls 0.025967 0.000040
ViewEditor.Controls Ensure child controls called. 0.025991 0.000023
ViewEditor.CreateChildControls Done 0.026014 0.000023
aspx.page End ProcessPostData 0.049396 0.023382
ViewEditor.OnLoad() Loading 0.049514 0.000118
ViewEditor.OnLoad() load done 0.049540 0.000026
aspx.page Begin ProcessPostData Second Try 0.049634 0.000094
aspx.page End ProcessPostData Second Try 0.049691 0.000056
aspx.page Begin Raise ChangedEvents 0.049715 0.000024
ViewEditor._ddlViews_SelectedIndexChanged
_ddlViews_SelectedIndexChanged started. 0.050883 0.001169
ViewEditor.InitializeControlData() Starting data retrieval 0.050982
0.000099
ViewEditor.SelectedViewId SelectedViewId set to
0xf0b00096ad7c0000010877db8fb6800c 0.051023 0.000041
ViewEditor.SelectedViewId SelectedViewId =
0xf0b00096ad7c0000010877db8fb6800c 0.051047 0.000024
ViewEditor.GetControlData Starting... 0.051098 0.000051
ViewEditor.SelectedViewId SelectedViewId =
0xf0b00096ad7c0000010877db8fb6800c 0.051197 0.000099
ViewEditor.GetControlData Done. 0.718004 0.666807
ViewEditor.InitializeControlData() Cache entry created as
_ASP.summary_aspxveSummaryalfred 0.720741 0.002737
ViewEditor.SelectedViewId SelectedViewId set to
0xf0b001b0928200000108b00caa00957b 0.720816 0.000075
ViewEditor.createQuickFilterControls Starting... 0.720833 0.000017
ViewEditor.CreateQuickFilterDropDownControl Starting 0.720870 0.000037
ViewEditor.CreateQuickFilterDropDownControl Done 0.722047 0.001176
ViewEditor.CreateQuickFilterDropDownControl Starting 0.722082 0.000035
ViewEditor.CreateQuickFilterDropDownControl Done 0.727788 0.005706
ViewEditor.CreateQuickFilterDropDownControl Starting 0.727839 0.000051
ViewEditor.CreateQuickFilterDropDownControl Done 0.727928 0.000089
ViewEditor.CreateQuickFilterDropDownControl Starting 0.727949 0.000021
ViewEditor.CreateQuickFilterDropDownControl Done 0.728002 0.000052
ViewEditor.CreateQuickFilterDropDownControl Starting 0.728021 0.000019
ViewEditor.CreateQuickFilterDropDownControl Done 0.728085 0.000064
ViewEditor.createQuickFilterControls Done... 0.728104 0.000018
ViewEditor.InitializeControlData() data retrieval complete 0.728120
0.000016
ViewEditor.CreateChildControls Starting 0.728136 0.000016
ViewEditor.Controls Getting controls 0.728150 0.000015
ViewEditor.Controls Ensure child controls called. 0.728164 0.000014
ViewEditor.CreateGQViewsDropDown Starting 0.728698 0.000534
ViewEditor.SelectedViewId SelectedViewId set to
0xf0b00096ad7c0000010877db8fb6800c 0.728787 0.000089
ViewEditor.Controls Getting controls 0.728805 0.000018
ViewEditor.Controls Ensure child controls called. 0.728821 0.000015
ViewEditor.CreateGQViewsDropDown Done 0.728837 0.000016
ViewEditor.Controls Getting controls 0.728907 0.000070
ViewEditor.Controls Ensure child controls called. 0.728924 0.000017
ViewEditor.Controls Getting controls 0.729163 0.000239
ViewEditor.Controls Ensure child controls called. 0.729193 0.000030
ViewEditor.Controls Getting controls 0.729210 0.000017
ViewEditor.Controls Ensure child controls called. 0.729225 0.000015
ViewEditor.Controls Getting controls 0.729240 0.000015
ViewEditor.Controls Ensure child controls called. 0.729255 0.000015
ViewEditor.Controls Getting controls 0.729270 0.000015
ViewEditor.Controls Ensure child controls called. 0.729285 0.000015
ViewEditor.Controls Getting controls 0.729301 0.000015
ViewEditor.Controls Ensure child controls called. 0.729315 0.000015
ViewEditor.Controls Getting controls 0.729355 0.000040
ViewEditor.Controls Ensure child controls called. 0.729372 0.000017
ViewEditor.CreateRefreshButton Starting 0.729388 0.000017
ViewEditor.Controls Getting controls 0.729408 0.000019
ViewEditor.Controls Ensure child controls called. 0.729423 0.000016
ViewEditor.CreateRefreshButton done 0.729439 0.000015
ViewEditor.Controls Getting controls 0.729466 0.000027
ViewEditor.Controls Ensure child controls called. 0.729482 0.000016
ViewEditor.CreateChildControls Done 0.729498 0.000016
ViewEditor.OnViewChanged() OnViewChanged started. 0.729853 0.000355
Summary.aspx.cs.GetSummaryData() getting data... 0.729917 0.000064
ViewEditor.SelectedViewId SelectedViewId =
0xf0b00096ad7c0000010877db8fb6800c 0.730371 0.000455
Summary.aspx.cs.uwgSummary_InitializeLayout initializing layout...
1.070761 0.340390
Summary.aspx.cs.uwgSummary_InitializeLayout layout initialized.
1.070818 0.000057
Summary.aspx.cs.GetSummaryData() data retrieval complete. 1.070850
0.000033
ViewEditor.OnViewChanged() OnViewChanged completed. 1.070867 0.000017
ViewEditor._ddlViews_SelectedIndexChanged
_ddlViews_SelectedIndexChanged completed. 1.070882 0.000015
aspx.page End Raise ChangedEvents 1.070897 0.000015
aspx.page Begin Raise PostBackEvent 1.070912 0.000015
Unhandled Execution Error
Object reference not set to an instance of an object.
at
System.Web.UI.WebControls.Button.System.Web.UI.IPo stBackEventHandler.RaisePostBackEvent(String
eventArgument)
at System.Web.UI.Page.RaisePostBackEvent(IPostBackEve ntHandler
sourceControl, String eventArgument)
at System.Web.UI.Page.RaisePostBackEvent(NameValueCol lection
postData)
at System.Web.UI.Page.ProcessRequestMain() 1.073220 0.002309
Control Tree
Control Id Type Render Size Bytes (including children) Viewstate Size
Bytes (excluding children)

 
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