Develop Reference

Strange conflict between get postback control and RegisterStartupScript

Please consider this scenario:
I have a simple page and I want to log all controls causing postback. I create this simple page. It contains a grid to show some URLs and when user click on an icon a new tab should open:
<form id="form1" runat="server">
<div>
<table style="width: 100%;">
<tr>
<td style="background-color: #b7ffbb; text-align: center;" colspan="2">
<asp:Button ID="Button3" runat="server" Text="Click Me First" Height="55px" OnClick="Button3_Click" />
</td>
</tr>
<tr>
<td style="background-color: #f1d8fe; text-align: center;" colspan="2">
<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="false" BackColor="White" OnRowCommand="GridView1_RowCommand">
<Columns>
<asp:BoundField DataField="SiteAddress" HeaderText="Address" />
<asp:TemplateField>
<ItemTemplate>
<asp:ImageButton ID="ImageButton1" ImageUrl="~/download.png" runat="server" CommandArgument='<%# Eval("SiteAddress") %>' CommandName="GoTo" Height="32px" Width="32px" />
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
</td>
</tr>
</table>
</div>
</form>
and code behind:
public partial class WebForm2 : Page
{
protected void Page_Load(object sender, EventArgs e)
{
}
protected void Button3_Click(object sender, EventArgs e)
{
List<Address> Addresses = new List<Address>()
{
new Address(){ SiteAddress = "https://google.com" },
new Address(){ SiteAddress = "https://yahoo.com" },
new Address(){ SiteAddress = "https://stackoverflow.com" },
new Address(){ SiteAddress = "https://learn.microsoft.com/}" }
};
GridView1.DataSource = Addresses;
GridView1.DataBind();
}
protected void GridView1_RowCommand(object sender, GridViewCommandEventArgs e)
{
ScriptManager.RegisterStartupScript(this, this.GetType(), "MyScript", "window.open('" + e.CommandArgument.ToString() + "', '_blank')", true);
}
}
class Address
{
public string SiteAddress { get; set; }
}
every thing is fine till here. Now I create a base class for all of my pages and add below codes for finding postback control:
public class MyPageBaseClass : Page
{
protected override void OnInit(EventArgs e)
{
if (!IsPostBack)
{
}
else
{
var ControlId = GetPostBackControlName(); <------
//Log ControlId
}
base.OnInit(e);
}
private string GetPostBackControlName()
{
Control control = null;
string ctrlname = Page.Request.Params["__EVENTTARGET"];
if (ctrlname != null && ctrlname != String.Empty)
{
control = Page.FindControl(ctrlname);
}
else
{
foreach (string ctl in Page.Request.Form)
{
Control c;
if (ctl.EndsWith(".x") || ctl.EndsWith(".y"))
{
string ctrlStr = ctl.Substring(0, ctl.Length - 2);
c = Page.FindControl(ctrlStr);
}
else
{
c = Page.FindControl(ctl);
}
if (c is System.Web.UI.WebControls.Button ||
c is System.Web.UI.WebControls.ImageButton)
{
control = c;
break;
}
}
}
if (control != null)
return control.ID;
else
return string.Empty;
}
}
and change this line:
public partial class WebForm2 : MyPageBaseClass
Now when I click on icons grid view disappears...(STRANGE...) and nothing happened. When I comment specified line then every thing will be fine...(STRANGE...).
In GetPostBackControlName nothings changed to Request but I don't know why this happened. I checked and I see if I haven't RegisterStartupScript in click event every thing is fine. Please help we to solve this problem.
Thanks

when I click on icons grid view disappears...
ASP.Net page class object instances only live long enough to serve one HTTP request, and each HTTP request rebuilds the entire page by default.
Every time you do a postback, you have a new HTTP request and therefore a new page class object instance and a completely new HTML DOM in the browser. Any work you've done for a previous instance of the page class — such as bind a list of addresses to a grid — no longer exists.
You could fix this by also rebuilding your grid code on each postback, but what I'd really do is skip the whole "RegisterStartupScript" mess and instead make the grid links open the window directly, without a postback at all.

The problem is related to OnInit event. I replaced it with OnPreLoad and every things is fine now.
For search engines: OnInit event has conflict with RegisterStartupScript

Button created from code behind disappeared after click [duplicate]

Actually, I am Creating 1 TextBox on Pageload and adding that TextBox to Panel.
Now, I have a LinkButton like Add Another.
I am entering Text in that TextBox and if needed I need to Create New TextBox,by clicking Add Another LinkButton.
Actually, I am able to get the count and recreate the TextBoxes.
But,the Problem is that, My Entered text in the Previously Generated Textboxes is Missing.
Can Anyone,Suggest me a solution for this?
protected void Page_Load(object sender, EventArgs e)
{
try
{
if (!IsPostBack)
{
for (int i = 0; i < 5; i++)
{
TableRow row = new TableRow();
for (int j = 0; j < 5; j++)
{
TableCell cell = new TableCell();
TextBox tb = new TextBox();
tb.ID = "TextBoxRow_" + i + "Col_" + j;
cell.Controls.Add(tb);
row.Cells.Add(cell);
}
Table1.Rows.Add(row);
}
}
}
catch (Exception ex)
{
throw;
}
}
This is a Sample Code, the same code is written in Button_Click Also
protected void ASPxButton1_Click(object sender, EventArgs e)
{
int k = Table1.Controls.Count;
}
I am getting a Count=0 on Button_Click.

All you need to do is to re-instantiate / reinitialize dynamic controls before or within page load event each and every time during postback and add this control to page / forms / placeholders. Then, the posted data will automatically be assigned to the control by calling the LoadPostData method by the parent control.
check the article and how to write code for dynamic control -
How to maintain dynamic control events, data during postback in asp.net

When using dynamic controls, you must remember that they will exist only until the next postback.ASP.NET will not re-create a dynamically added control. If you need to re-create a control multiple times, you should perform the control creation in the PageLoad event handler ( As currently you are just creating only for first time the TextBox using Condition: !IsPostabck ). This has the additional benefit of allowing you to use view state with your dynamic control. Even though view state is normally restored before the Page.Load event, if you create a control in the handler for the PageLoad event, ASP.NET will apply any view state information that it has after the PageLoad event handler ends.
So, Remove the Condition: !IsPostback, So that each time the page Loads, The TextBox control is also created. You will also see the State of Text box saved after PageLoad handler completes. [ Obviously you have not disabled ViewState!!! ]
Example:
protected void Page_Load(object sender, EventArgs e)
{
TextBox txtBox = new TextBox();
// Assign some text and an ID so you can retrieve it later.
txtBox.ID = "newButton";
PlaceHolder1.Controls.Add(txtBox);
}
Now after running it, type anything in text box and see what happens when you click any button that causes postback. The Text Box still has maintained its State!!!

The dynamically generated control do not maintain state. You have to maintain it at your own. You can use some hidden field to keep the state of controls, which will be used on server side to extract the state. Asp.net uses hidden field to maintain the state between requests, you can see __VIEWSTATE in the source.
In ASP.NET pages, the view state represents the state of the page when
it was last processed on the server. It's used to build a call context
and retain values across two successive requests for the same page. By
default, the state is persisted on the client using a hidden field
added to the page and is restored on the server before the page
request is processed. The view state travels back and forth with the
page itself, but does not represent or contain any information that's
relevant to client-side page display, Reference.

Just remove this line
if (!IsPostBack)

This is My final answer after working a lot with Dynamic Controls
.aspx
<form id="form1" runat="server">
<asp:ScriptManager ID="ScriptManager1" runat="server">
</asp:ScriptManager>
<div style="text-align: center">
<div style="background-color: Aqua; width: 250px;">
<br />
<asp:UpdatePanel ID="UpdatePanel1" runat="server">
<ContentTemplate>
<asp:PlaceHolder runat="server" ID="myPlaceHolder"></asp:PlaceHolder>
</ContentTemplate>
<Triggers>
<asp:AsyncPostBackTrigger ControlID="btnAddTextBox" EventName="Click" />
</Triggers>
</asp:UpdatePanel>
<br />
</div>
<br />
<asp:Button ID="btnAddTextBox" runat="server" Text="Add TextBox" OnClick="btnAddTextBox_Click" />
<br /><br />
<asp:UpdatePanel ID="UpdatePanel2" runat="server">
<ContentTemplate>
<asp:Button runat="server" ID="MyButton" Text="Get Values." OnClick="MyButton_Click" />
<br /><br />
<asp:Label runat="server" ID="MyLabel"></asp:Label>
</ContentTemplate>
</asp:UpdatePanel>
</div>
</form>
.aspx.cs
static int myCount = 0;
private TextBox[] dynamicTextBoxes;
protected void Page_PreInit(object sender, EventArgs e)
{
Control myControl = GetPostBackControl(this.Page);
if ((myControl != null))
{
if ((myControl.ClientID.ToString() == "btnAddTextBox"))
{
myCount = myCount + 1;
}
}
}
protected override void OnInit(EventArgs e)
{
base.OnInit(e);
dynamicTextBoxes = new TextBox[myCount];
int i;
for (i = 0; i < myCount; i += 1)
{
TextBox textBox = new TextBox();
textBox.ID = "myTextBox" + i.ToString();
myPlaceHolder.Controls.Add(textBox);
dynamicTextBoxes[i] = textBox;
LiteralControl literalBreak = new LiteralControl("<br />");
myPlaceHolder.Controls.Add(literalBreak);
}
}
protected void btnAddTextBox_Click(object sender, EventArgs e)
{
// Handled in preInit due to event sequencing.
}
protected void MyButton_Click(object sender, EventArgs e)
{
MyLabel.Text = "";
foreach (TextBox tb in dynamicTextBoxes)
{
MyLabel.Text += tb.Text + " :: ";
}
}
public static Control GetPostBackControl(Page thePage)
{
Control myControl = null;
string ctrlName = thePage.Request.Params.Get("__EVENTTARGET");
if (((ctrlName != null) & (ctrlName != string.Empty)))
{
myControl = thePage.FindControl(ctrlName);
}
else
{
foreach (string Item in thePage.Request.Form)
{
Control c = thePage.FindControl(Item);
if (((c) is System.Web.UI.WebControls.Button))
{
myControl = c;
}
}
}
return myControl;
}

When you are working with dynamic controls they will not able to maintain its state during postback and their data lost Cause they dont have any viewstate to maintain their data.
You only need to maintain the created controls data into ViewState
dynamically and loads the data into page at the time of postback and you
done.
public Dictionary<Guid, string> UcList
{
get { return ViewState["MyUcIds"] != null ? (Dictionary<Guid, string>)ViewState["MyUcIds"] : new Dictionary<Guid, string>(); }
set { ViewState["MyUcIds"] = value; }
}
public void InitializeUC()
{
int index = 1;
foreach (var item in UcList)
{
var myUc = (UserControls_uc_MyUserControl)LoadControl("~/UserControls/uc_MyUserControl.ascx");
myUc.ID = item.Value;
pnlMyUC.Controls.AddAt(index, myUc);
index++;
}
}
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
LoadControl();
else
InitializeUC();
}

Actually, I have used Javascript for accomplishing my task.
and it goes like this :
<form id="form1" runat="server" enctype="multipart/form-data" method="post">
<span style="font-family: Arial">Click to add files</span>
<input id="Button1" type="button" value="add" onclick="AddFileUpload()" />
<br />
<br />
<div id="FileUploadContainer">
<!--FileUpload Controls will be added here -->
</div>
<asp:HiddenField ID="HdFirst1" runat="server" Value="" />
<br />
<asp:Button ID="btnUpload" runat="server" Text="Upload" OnClick="btnUpload_Click" />
</form>
Script :
<script type="text/javascript">
var counter = 0;
function AddFileUpload() {
var div = document.createElement('DIV');
div.innerHTML = '<input id="file' + counter + '"name = "file' + counter + '"type="text"/><input id="file' + counter + '" name = "file' + counter + '" type="file" /><input id="Button' + counter + '" type="button" value="Remove" onclick = "RemoveFileUpload(this)" />';
document.getElementById("FileUploadContainer").appendChild(div);
counter++;
}
function RemoveFileUpload(div) {
document.getElementById("FileUploadContainer").removeChild(div.parentNode);
}
function mydetails(div) {
var info;
for (var i = 0; i < counter; i++) {
var dd = document.getElementById('file' + i).value;
info = info + "~" + dd;
}
document.getElementById('<%= HdFirst1.ClientID %>').value = info;
}
</script>
and In the Upload_Click Button :
for (int i = 0; i < Request.Files.Count; i++)
{
string strname = HdFirst1.Value;
string[] txtval = strname.Split('~');
HttpPostedFile PostedFile = Request.Files[i];
if (PostedFile.ContentLength > 0)
{
string FileName = System.IO.Path.GetFileName(PostedFile.FileName);
// string textname=
//PostedFile.SaveAs(Server.MapPath("Files\\") + FileName);
}
}

Dynamically change label text in aspx page without postback or page-load

I am currently in the process of creating an asp.net webforms site in c#.
My goal with this website is to be able to receive mqtt messages from a mqtt broker that I currently have running, and disply them on a simple website.
I currently have the communication up and running and can subscribe and receive messages just as I wish, but my problem is that after receiving the messages in my code-behind, I am not able to dynamically display them in my aspx! I am currently trying to display a value in an asp:label, and every time I receive a new value I would like to update the label-text to reflect this.
Again my code-behind is working as intended, but my problem seems to be that the messages from my mqtt broker is not causing a page-load or postback, which means that my aspx are not getting refreshed. I have tried to solve this using JavaScript, but this doesn't seem to work! Here is a simplified version of my code:
Aspx:
<%# Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="proof_of_concept.WebForm1" %>
<head runat="server">
<script type="text/javascript">
var jsVariable1;
function GetValues(){
var someVar1 = "<%=Variable1 %>";
if(someVar1 != null && someVar1 != jsVariable1){
jsVariable1 == someVar1;
$('#Label1').innerHTML = "Variable 1 =<br/>" + jsVariable1;
}
setTimeout(GetValues, 5000);
}
GetValues();
</script>
</head>
<body>
<form id="form1" runat="server">
<div class="container" id="container">
<img src="/Images/TestImage.jpg" style="width:100%;" />
<div class="position1">
<asp:Label ID="Label1" runat="server" Text="Var1: <br/> Value"></asp:Label>
</div>
</div>
</form>
</body>
.cs:
namespace proof_of_concept
{
public partial class WebForm1 : System.Web.UI.Page
{
private static MqttClient myClient;
public String Variable1 = "No data yet";
protected void Page_Load(object sender, EventArgs e)
{
Page.DataBind();
if (!IsPostBack)
{
//Initialize connection to the mqtt broker (with a hardcoded URL)
myClient = new MqttClient("myBrokerurl", 1883, false, null, null, 0, null, null);
//Connect to the broker with an autogenerated User-ID
myClient.Connect(Guid.NewGuid().ToString());
//Check if the connection was established
Debug.WriteLine("Client connected: " + myClient.IsConnected);
//Subscribe to a topic at the broker (Again in this example the topic has been hardcoded)
myClient.Subscribe(new string[] { "mySubscribedTopic/#" },
new byte[] { MqttMsgBase.QOS_LEVEL_AT_LEAST_ONCE });
//Sets up an eventhandler for received messages to the subscribed topic(s)
myClient.MqttMsgPublishReceived += myClient_MqttMsgPublishReceived;
}
}
protected void myClient_MqttMsgPublishReceived(object sender, MqttMsgPublishEventArgs e)
{
//Check if a message was received
Debug.WriteLine("Received = " + Encoding.UTF8.GetString(e.Message) + " on topic " + e.Topic);
variableSelector(e.Topic, Encoding.UTF8.GetString(e.Message));
}
protected void variableSelector(String topicString, String messageString)
{
if (topicString.Contains("var1") == true)
{
Variable1 = messageString;
//Databinding here was a test that didnt seem to do anything
Page.DataBind();
}
}
}
I am not sure if my JavaScript is relevant, but I wrote it as an attempted workaround to my problem (which is that the label-text is not getting updated when I receive new messages from my broker).

It seems to me that the Broker is sending messages to the server of device A and the client of your page is on machine B and you are trying to synchronize, if this is the case, update a database on the server and use something similar with my example.
In my example i will focus on "I have tried to solve this using javascript, but this doesnt seem to work!".
Either way, you have chosen the wrong technology to do this, WebForms will give you a lot of headache.
Use Asp.Net MVC ... will be much easier.
Page
<form id="form1" runat="server">
<asp:ScriptManager ID="MyScriptManager" runat="server">
</asp:ScriptManager>
<asp:UpdatePanel ID="MyUpdatePanel" runat="server">
<ContentTemplate>
<asp:Label ID="MyLabel" runat="server"> Postback number <%= Counter %></asp:Label>
</ContentTemplate>
</asp:UpdatePanel>
</form>
Code-Behind
public partial class MyPage: System.Web.UI.Page
{
protected int Counter { get; set; }
protected void Page_Load(object sender, EventArgs e)
{
if (IsPostBack)
{
// MyUpdatePanel will perform a async post-back every 1000 milliseconds
int _newCounter;
var newCount = Request.Form["__EVENTARGUMENT"];
if (newCount != null)
{
if (int.TryParse(newCount, out _newCounter))
{
Counter = _newCounter;
}
}
return;
}
// Loading javascript that will trigger the postback
var _pageType = this.GetType();
var script =
string.Concat(
"var counter = 0;",
"setInterval(function() { ",
"__doPostBack('", MyUpdatePanel.UniqueID, "', counter);",
"counter++; }, 1000);");
ClientScript.RegisterStartupScript(_pageType, "AutoPostBackScript", script, true);
}
}

Button click event triggered by enter key ... why?

this is my Page_Load
protected void Page_Load(object sender, EventArgs e)
{
string Error = "";
//Any attempt to login from another page met with an error is bounced here. We then display the error message. We do this because many other pages have a css dropdown with limited options and no warning label.
if (!IsPostBack)
{
try { Error = Session["LoginError"].ToString(); }
catch { }
Session["LoginError"] = "";
// if (Error.Length > 0) { WarningLbl.Text = Error; }
LoadPageText();
}
else
{
Enroll();
}
}
on PostBack, when I press enter ... Enroll(); executes, but it also executes the following button_event
this is the ASP
<td style="width: 75px; text-align: center; vertical-align: top;">
<asp:Button ID="FrenchBtn" runat="server" BackColor="Transparent" BorderStyle="None" CssClass="clickable" Font-Bold="True" Font-Names="Arial" Font-Size="X-Small" ForeColor="White" OnClick="FrenchBtn_Click" onmouseout="this.style.color = 'white';" onmouseover="this.style.color = 'yellow';" Text="Button" />
</td>
here is the CSS:
.clickable {
z-index: 0;
cursor: pointer;
}
protected void FrenchBtn_Click(object sender, EventArgs e)
{
SessionVars.Current.varLanguage = "French";
Response.Redirect("~/Account/Enroll.aspx");
}
Note: I have not pressed the button to execute this; however, this is the first "clickable" event on the screen. Why is this executing? is there some attribute or property or sequence that is causing this to execute?

This is called form's default submit button. Make sure it isn't registered within the form or somewhere else on the page (check containers where you button is placed in, pages and panels have this functionality)
<form id="form1" runat="server" defaultbutton="FrenchBtn">
http://www.codeproject.com/Tips/229011/How-to-make-a-button-the-default-button-on-enter

Ajax TabContainer intermittently dissapears on Postback

I am developing a GIS web app (mapping) in C# ASP.net.
I have an Ajax TabContainer housing several TabPanels with a table. The table contains other content such as the map window, scale bar etc (all from the ESRI WebAdf toolkit).
Here's a slimmed down version of my table without the other content...
<table id="MainTable>
<tr>
<td>
<ajax:TabContainer runat="server" ActiveTabIndex="0" id="TabContainer" CssClass="ajax__tab_xp">
<ajax:TabPanel runat="server" HeaderText="Online Mapping Service" ID="TabPanel1">
</ajax:TabPanel>
<ajax:TabPanel ID="TabPanel2" runat="server" HeaderText="Postcode">
</ajax:TabPanel>
<ajax:TabPanel ID="TabPanel3" runat="server" HeaderText="Coordinates">
<ContentTemplate>
</ajax:TabPanel>
</ajax:TabContainer>
</td>
</tr>
</table>
On Postback at runtime my Tabcontainer sometimes dissapears. This issue is not browser specific.
So far I have tried with no success to...
Set Z-Index with Relative positioning for the TabContainer
Include a JQuery script to 'show' the TabContainer...
<script type="text/javascript" language="javascript">
$(document).ready(function() {
$("#TabContainer").show();
});
</script>
Is there some C# I can include in the code behind along the lines of?...
Public void page_Load(object sender, EventArgs e)
{
TabContainer.show()
}
Fairly new to programming and trying to figure out how to 'always show' or 'always ontop' the TabContainer.
Thanks

I'm not sure if this is due to the fact that you cleaned your code before posting it here but you are missing tags.
The code on your aspx should look like this :
<AjaxToolkit:TabContainer ID="TabContainer" runat="server">
<AjaxToolkit:TabPanel ID="TabPanel1" runat="server">
<ContentTemplate>
Your asp/html code goes here
</ContentTemplate>
</AjaxToolkit:TabPanel>
</AjaxToolkit:TabContainer>

Ok, sorted this. There was an issue with the AJAX Toolkit not posting back client side...
<script language="javascript" type="text/javascript">
// Solution to sys.invalidoperationexception bug
Sys.Application.initialize = function Sys$_Application$initialize() {
if (!this._initialized && !this._initializing) {
this._initializing = true;
var loadMethodSet = false;
var initializeDelegate = Function.createDelegate(this, this._doInitialize);
if (document.addEventListener) {
loadMethodSet = true;
document.addEventListener("DOMContentLoaded", initializeDelegate, false);
}
if (/WebKit/i.test(navigator.userAgent)) {
loadMethodSet = true;
this._load_timer = setInterval(function() {
if (/loaded|complete/.test(document.readyState)) {
initializeDelegate();
}
}, 10);
}
else {
/*#cc_on#*/
/*#if (#_win32)
loadMethodSet = true;
document.write("<script id=__ie_onload defer src=BLOCKED SCRIPTvoid(0)><\/scr" + "ipt>");
var deferScript = document.getElementById("__ie_onload");
if (deferScript) {
deferScript.onreadystatechange = function() {
if (this.readyState == "complete") {
initializeDelegate();
}
};
}
/*#end#*/
}
// only if no other method will execute initializeDelegate is
// it wired to the window's load method.
if (!loadMethodSet) {
$addHandler(window, "load", initializeDelegate);
}
}
}
Sys.Application._doInitialize = function Sys$_Application$_doInitialize() {
if (this._load_timer !== null) {
clearInterval(this._load_timer);
this._load_timer = null;
}
Sys._Application.callBaseMethod(this, 'initialize');
var handler = this.get_events().getHandler("init");
if (handler) {
this.beginCreateComponents();
handler(this, Sys.EventArgs.Empty);
this.endCreateComponents();
}
this.raiseLoad();
this._initializing = false;
}
Sys.Application._loadHandler = function Sys$_Application$_loadHandler() {
if (this._loadHandlerDelegate) {
Sys.UI.DomEvent.removeHandler(window, "load",
this._loadHandlerDelegate);
this._loadHandlerDelegate = null;
}
this._initializing = true;
this._doInitialize();
}
</script>