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Inject a textbox in WebForms and retain the value on postback

I have a WebForms page that I would like to inject some additional controls into at runtime. Currently I am achieving this in the Page_Load event using a Literal control.
For example the page looks like this (note that the TextBox1 is not an asp control just to show that it works):
<asp:Content ID="BodyContent" ContentPlaceHolderID="MainContent" runat="server">
<input id="TextBox1" type="text" runat="server"/>
<asp:Literal ID="Literal1" runat="server" Visible="false"></asp:Literal>
<asp:Button ID="Button1" runat="server" Text="Button" OnClick="Button1_Click" />
</asp:Content>
And the code behind:
protected void Page_Load(object sender, EventArgs e)
{
Literal1.Visible = true;
if (!IsPostBack) Literal1.Text = "<input id=\"TextBox2\" type=\"text\" runat=\"server\"/>";
}
This works fine and both textboxes appear on the screen but if I type a value in to both and trigger a postback only the value of TextBox1 is retained.
I have tried moving my code to OnPreRender and OnPreLoad but still have the same issue.
I have noticed that when I view the page source TextBox1 has a UniqueId (e.g. ctl00$MainContent$TextBox1) while Textbox2 still has runat="server" as an attribute.

You can't inject server controls like this. You would need to add them as suggested in #Arvin's answer.
However, you use inject non-ASP.NET HTML controls similar to what you are doing and get their values.
From your code change the input's id to a name and drop the runat="server":
protected void Page_Load(object sender, EventArgs e)
{
Literal1.Visible = true;
if (!IsPostBack) Literal1.Text = "<input name=\"TextBox2\" type=\"text\" />";
}
Then you can get it's value on postback:
string textbox2value = Request.Form["TextBox2"];
Then, if you want to add the control on postback with it's value:
Literal1.Text = "<input name=\"TextBox2\" type=\"text\" value=\"" +
Server.HTMLEncode(textbox2value) + "\" />";

if you want to inject a textbox you should use placeholder like this :
<input id="TextBox1" type="text" runat="server"/>
<asp:PlaceHolder ID="plh" runat="server"></asp:PlaceHolder>
<asp:Button ID="Button1" runat="server" Text="Button" OnClick="Button1_Click" />
protected void Page_Load(object sender, EventArgs e)
{
TextBox TextBox = new TextBox();
TextBox.ID = "TextBox2";
plh.Controls.Add(TextBox);
}
protected void Button1_Click(object sender, EventArgs e)
{
var Text1 = TextBox1.Value;
var Text2 = Request.Form["TextBox2"];
}

C# Repeater focusing the first element after DataSource is changed

I have a Repeater with a certain DataSource (consisting of a list of images). The Repeater holds ImageButtons.
The aspx:
<asp:Panel ID="panSearch" runat="server" ScrollBars="Vertical" BorderColor="#333333" BorderStyle="Inset" Width="500" Height="200">
<asp:Repeater ID="Repeater" runat="server">
<ItemTemplate>
<asp:ImageButton OnClick="imgSearchResult_Click" BackColor="#333333" ID="imgSearchResult" height="32" width="32" runat="server" ImageUrl='<%# Eval("ImageUrl") %>'/>
</ItemTemplate>
</asp:Repeater>
</asp:Panel>
Additionally, I have a TextBox, which has a TextChanged-event in code-behind. I do a few things in there and at the end, my Repeater's DataSource will be overwritten with a new List of images (those images are put into the ImageButtons).
Repeater.DataSource = ImageList;
Repeater.DataBind();
My problem: Whenever my Repeater.DataSource is changed, it "clicks" the first ImageButton inside the Repeater. How do I prevent that from happening?
Full code:
My TextBox:
<asp:TextBox ID="textSearch" runat="server" Width="80" OnTextChanged="textSearch_TextChanged" ForeColor="Black" />
My TextChanged event:
protected void textSearch_TextChanged(object sender, EventArgs e)
{
string[] filesindirectory = Directory.GetFiles(Server.MapPath("~/Images/ORAS"));
List<System.Web.UI.WebControls.Image> ImageList = new List<System.Web.UI.WebControls.Image>(filesindirectory.Count());
foreach (string item in filesindirectory)
{
System.Web.UI.WebControls.Image myImage= new System.Web.UI.WebControls.Image();
myImage.ImageUrl = (String.Format("~/Images/ORAS/{0}", System.IO.Path.GetFileName(item)));
ImageList.Add(myImage);
}
Repeater.DataSource = ImageList;
Repeater.DataBind();
}
When I click on an ImageButton inside the Repeater (which is executed when the text in my TextBox is changed):
protected void imgSearchResult_Click(object sender, ImageClickEventArgs e)
{
var selectedImage = sender as ImageButton;
if (img1.ImageUrl == "~/Images/ORAS/Empty/000.png")
{
img1.ImageUrl = selectedImage.ImageUrl;
}
else if (img2.ImageUrl == "~/Images/ORAS/Empty/000.png")
{
img2.ImageUrl = selectedImage.ImageUrl;
}
else if (img3.ImageUrl == "~/Images/ORAS/Empty/000.png")
{
img3.ImageUrl = selectedImage.ImageUrl;
}
else if (img4.ImageUrl == "~/Images/ORAS/Empty/000.png")
{
img4.ImageUrl = selectedImage.ImageUrl;
}
else if (img5.ImageUrl == "~/Images/ORAS/Empty/000.png")
{
img5.ImageUrl = selectedImage.ImageUrl;
}
else if (img6.ImageUrl == "~/Images/ORAS/Empty/000.png")
{
img6.ImageUrl = selectedImage.ImageUrl;
}
else
{
ErrorMessage("Please remove one Image first!", true);
}
}
Pageload:
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
img1.ImageUrl = "~/Images/ORAS/Empty/000.png";
img2.ImageUrl = "~/Images/ORAS/Empty/000.png";
img3.ImageUrl = "~/Images/ORAS/Empty/000.png";
img4.ImageUrl = "~/Images/ORAS/Empty/000.png";
img5.ImageUrl = "~/Images/ORAS/Empty/000.png";
img6.ImageUrl = "~/Images/ORAS/Empty/000.png";
LoadImages();
}
}
(LoadImages is almost 1:1 what's in my TextChanged function)

I really am not sure how (why) ASP.NET WebForms does it, but if you hit Enter and the form posts back, it will find the first control that implements IPostBackEventHandler and execute whatever event is bound to that. ImageButton implements it and so that's why it keeps firing the click event even though you didn't click on it. And, once again, only if you hit Enter.
I think that behaviour happens because the data posted back - __EVENTTARGET and __EVENTARGUMENT - are empty. Then ASP.NET goes bonkers.
You can solve it by putting a dummy button at the top of the page (or masterpage) and hide it using the style attribute. so:
<asp:Button ID="dummy" runat="server" style="display:none" />
Then in the init or load of your page (or masterpage) put
Form.DefaultButton = dummy.UniqueID;
That will force the button to capture the enter press instead of the arbitrary image button.

Dynamically Created Controls losing data after postback

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);
}
}

TextChanged doesn't fire

I am trying to generate textboxes when the I press button add more so this is the code for onclick
protected void Add_TextBoxes(object sender, EventArgs e)
{
int index = int.Parse(ViewState["pickindex"].ToString());
TextBox MyTextBox = new TextBox();
MyTextBox.ID = "tbautogenerated"+index.ToString();
MyTextBox.Text = "tbautogenerated" + index.ToString();
MyTextBox.Width= 250;
MyTextBox.MaxLength = 128;
MyTextBox.Attributes.Add("runat", "server");
MyTextBox.CausesValidation = false;
MyTextBox.AutoPostBack = true;
MyTextBox.TextChanged += new EventHandler(MyTextBox_TextChanged);
picktexts.Controls.Add(MyTextBox);
}
void MyTextBox_TextChanged(object sender, EventArgs e)
{
TextBox MyTextBox = sender as TextBox;
}
but when I change in the textbox the textChanged doesn't work !!! what's wrong ?
HTML Code
<asp:UpdatePanel ID="UpdatePanel2" runat="server">
<ContentTemplate>
<div id="picktexts" runat="server">
<asp:TextBox ID="txtAdress" runat="server" MaxLength="128" Width="250" />
<asp:RequiredFieldValidator ControlToValidate="txtAdress" Display="Dynamic" ID="rfvAddress" Text="* Required" runat="server" />
<asp:Button ID="bt_addtxtbox" runat="server" Text="Add more" OnClick="Add_TextBoxes" CausesValidation="false" />
</div>
</ContentTemplate>
</asp:UpdatePanel>

I think the event handlers are getting lost between posts. the way ASP.NET works, every time you post a page back to itself, all objects are instantiated again, and their state is recovered from the ViewState. Normally a control that's declared in the aspx would reassociate itself with events by the declaration in its tag, which is not the case here.
So try associating the event handlers again during the page load. Like this:
void Page_Load (object sender, EventArgs e)
{
foreach (Control c in picktexts.Controls)
{
((TextBox)c).TextChanged += new EventHandler(MyTextBox_TextChanged);
}
}
And see if it works.

Problem with a hyperlink

I put a hyperlink inside a datalist..
<ItemTemplate>
<asp:HyperLink ID="HyperLink1" runat="server">'<%# Eval("ThreadTitle") %>'</asp:HyperLink>
<br />
<br />
</ItemTemplate>
I want it to enable it to be pressed so that the datalist event will be triggered and transfer me to another page:
protected void DataList1_SelectedIndexChanged(object sender, EventArgs e)
{
Server.Transfer("AnswerQuestion.aspx?x=" + DataList1.DataKeyField + "&question=" + DataList1.SelectedValue + "&time=" + DateTime.Now);
}
Unfortunately, the link seems to be disabled and I cant press on it to trigger the DataList Selected event..
How can I make the hyperlink active ?

If you want to trigger a selecteditemchaned event use a LinkButton instead of hyperlink.
<asp:DataList ID="DataList1" runat="server"
onselectedindexchanged="DataList1_SelectedIndexChanged">
<ItemTemplate>
<asp:LinkButton ID="sjdj" runat="server" CommandName="Select">
<%# Container.DataItem %></asp:LinkButton>
</ItemTemplate>
</asp:DataList>
In the code behind have
protected void DataList1_SelectedIndexChanged(object sender, EventArgs e)
{
Server.Transfer("~/jjtestjj.aspx?" + DataList1.DataKeyField);
}

why arent you using the Hyperlink as a hyperlink?
You can set the NavigationURL and Text using the OnItemDataBound (or equivalent) event.
this code works with an asp:Repeater:
protected void Row_DataItem(object row, RepeaterItemEventArgs args)
{
if (args.Item.ItemType == ListItemType.AlternatingItem || args.Item.ItemType == ListItemType.Item)
{
var item = (DataItemPOCO)args.Item.DataItem;
var link = (HyperLink)args.Item.FindControl("HyperLink1");
link.Text = item.LinkText;
link.NavigateUrl = item.URL;
}
}