I've created a class library which exposes my back-end object model. I don't wish to databind straight to SQL or XML, as a surprising number of tutorials/demos out there seem to assume.
In my Page_Load(), within the if (!IsPostbak), I currently set all the values of my controls from the object model, and call Databind() on each control.
I have a button event handler which deletes an item from the object model (it's a List in this case) and rebinds it to the Repeater. First of all, this is messy - rebinding each time - but more importantly, no values are displayed when the page reloads. Should I put the databinding code outside the if statement in Page_Load()?
The second part of the question is regarding going back to basics - what's the best way to databind in Asp.net? I'm mainly interested in binding against lists and arrays. I would have imagined there being a way to tell a control (e.g. TextBox) to databind to a string variable, and for the string to always reflect the contents of the text box, and the text box to always reflect the contents of the string. I tried the <%#...%> syntax but got no further than using the code-behind as described above.
I've read several overviews of databinding, but nothing out there seems to do what I want - they all talk about linking DataSets to a SQL database!
Turning to the knowledge of StackOverflow.
You'll need to databind on every page load so you need to remove the code from within your !IsPostBack block.
When using a list or array handle the databinding event on the control. For a repeater you'll need to handle the ItemDataBound event.
This example has been modified from http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.repeater.itemdatabound.aspx:
<%# Page Language="C#" AutoEventWireup="True" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html >
<head>
<title>OnItemDataBound Example</title>
<script language="C#" runat="server">
void Page_Load(Object Sender, EventArgs e) {
ArrayList values = new ArrayList();
values.Add(new Evaluation("Razor Wiper Blades", "Good"));
values.Add(new Evaluation("Shoe-So-Soft Softening Polish", "Poor"));
values.Add(new Evaluation("DynaSmile Dental Fixative", "Fair"));
Repeater1.DataSource = values;
Repeater1.DataBind();
}
void R1_ItemDataBound(Object Sender, RepeaterItemEventArgs e) {
// This event is raised for the header, the footer, separators, and items.
// Execute the following logic for Items and Alternating Items.
if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem) {
if (((Evaluation)e.Item.DataItem).Rating == "Good") {
((Label)e.Item.FindControl("RatingLabel")).Text= "<b>***Good***</b>";
}
}
}
public class Evaluation {
private string productid;
private string rating;
public Evaluation(string productid, string rating) {
this.productid = productid;
this.rating = rating;
}
public string ProductID {
get {
return productid;
}
}
public string Rating {
get {
return rating;
}
}
}
</script>
</head>
<body>
<h3>OnItemDataBound Example</h3>
<form id="form1" runat="server">
<br />
<asp:Repeater id="Repeater1" OnItemDataBound="R1_ItemDataBound" runat="server">
<HeaderTemplate>
<table border="1">
<tr>
<td><b>Product</b></td>
<td><b>Consumer Rating</b></td>
</tr>
</HeaderTemplate>
<ItemTemplate>
<tr>
<td> <asp:Label Text='<%# DataBinder.Eval(Container.DataItem, "ProductID") %>' Runat="server"/> </td>
<td> <asp:Label id="RatingLabel" Text='<%# DataBinder.Eval(Container.DataItem, "Rating") %>' Runat="server"/> </td>
</tr>
</ItemTemplate>
<FooterTemplate>
</table>
</FooterTemplate>
</asp:Repeater>
<br />
</form>
</body>
</html>
EDIT:
In addition, (and you may already be aware of this) you'll need to persist your list/array somehow. You can go all the way back to the database and reconstitute the list there or you can store it in memory with cache, viewstate, or session as viable options depending on your needs.
Spring.NET Web will provide you with two-way databinding with nice, easy to maintain code. Give it a try!
Related
Ok, I've already learned that in order to keep the dynamic (created) controls and their viewstate in asp.net we must (re)create them in the Page init event, so they already exist within the page's control hierarchy before the view state is loaded.
As it says in this article.
There is no problem to achieve this behaviour if the criteria to create these controls is outside the web environment, for example a database. But what should I do if what I use to decide how many dynamic controls I have to create is actually a value that is in the controls?
I try to explain it with an example, maybe it's clearer:
Let's say that we have a textbox and two buttons. In the textbox I write the number of how many dynamic controls I want to create, for example 4 checkbox. When I hit the button1 the controls should be created. No problem. Then I check some checkboxes and hit the button2 just to fire a postback. Now I should recreate the controls in the page init event, like we said before, in order to maintain the controls and their state.
And here comes the problem. Because of I'm in the init stage I have no viewstate so I'm no able to access the value in the textbox that tells me how many dynamic checkbox should I create.
I thought that storing the value in the session object would do the trick, but it doesn't. The session object is no accessible as well.
Where can I save the value that it'll be accessible from the init event too?
Thanks and sorry for the long post!
First thing - textbox value is not stored/retrieved from view state, you cannot get textbox value from viewstate.
Coming to actual problem, here is the sequence of (imp) events init -> load view state -> bind postback data -> page load. You can retrieve textbox value only after bind postback data event (which actually takes posted data and binds to the textbox control).
In init only option is to use Request.Form{"textboxid"] to get the textbox value.
You are on the right track.
If you use TextBox, you do not need another ViewState to keep track of how many controls has been created, because TextBox control has its own ViewState already.
You can use either Page_Init or Page_Load to load control back.
<%# Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs"
Inherits="WebApplication2010.WebForm1" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:TextBox runat="server" ID="NumberTextBox" />
<asp:Button runat="server" ID="CreateControlButton"
OnClick="CreateControlButton_Click"
Text="Create Control" />
<br />
<asp:PlaceHolder runat="server" ID="PlaceHolder1"></asp:PlaceHolder>
</div>
</form>
</body>
</html>
using System;
using System.Web.UI;
namespace WebApplication2010
{
public partial class WebForm1 : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
if (IsPostBack)
{
int ids;
if (Int32.TryParse(NumberTextBox.Text, out ids))
{
for (int i = 0; i < ids; i++)
{
Control ctrl = Page.LoadControl("WebUserControl.ascx");
ctrl.ID = i.ToString();
PlaceHolder1.Controls.Add(ctrl);
}
}
}
}
protected void CreateControlButton_Click(object sender, EventArgs e)
{
}
}
}
<%# Control Language="C#" AutoEventWireup="true"
CodeBehind="WebUserControl.ascx.cs"
Inherits="WebApplication2010.WebUserControl" %>
<asp:CheckBox runat="server" ID="CheckBox1" />
<asp:Button runat="server" ID="Button1" OnClick="Button_Click"
Text="Post Back" />
<asp:Label runat="server" ID="Label1" />
<br />
using System;
namespace WebApplication2010
{
public partial class WebUserControl : System.Web.UI.UserControl
{
protected void Button_Click(object sender, EventArgs e)
{
Label1.Text = " This control was posted back.";
}
}
}
This is the common paradox with page lifecycle when you work with code behind. For example, you save the editing customerid in viewstate but controls need to bind on init to be able to read their posted values.
Best real life solution is to do what bound controls do on postback, call explicilately the LoadPostBackData on IPostBackDataHandler interface that all controls implement, after you have created them in Page Load event.
You should create an extension method for Controls and call it when needed:
control.DataBind();
control.LoadPostedData(); // extension method
In a user control, I've got a Repeater inside of an UpdatePanel (which id displayed inside of a ModalPopupExtender. The Repeater is databound using an array list of MyDTO objects. There are two buttons for each Item in the list. Upon binding the ImageURL and CommandArgument are set.
This code works fine the first time around but the CommandArgument is wrong thereafter. It seems like the display is updated correctly but the DTO isn't and the CommandArgument sent is the one that has just been removed.
Can anybody spot any problems with the code?
Edit : I've just added a CollapsiblePanelExtender to the code. When I now delete an item and expand the panel, the item that was previously deleted (and gone from the display) has come back. It seems that the Repeater hasn't been rebuilt correctly under the bonnet.
ASCX
<asp:UpdatePanel ID="ViewDataDetail" runat="server" ChildrenAsTriggers="true">
<Triggers>
<asp:PostBackTrigger ControlID="ViewDataCloseButton" />
<asp:AsyncPostBackTrigger ControlID="DataRepeater" />
</Triggers>
<ContentTemplate>
<table width="100%" id="DataResults">
<asp:Repeater ID="DataRepeater" runat="server" OnItemCommand="DataRepeater_ItemCommand" OnItemDataBound="DataRepeater_ItemDataBound">
<HeaderTemplate>
<tr>
<th><b>Name</b></th>
<th><b> </b></th>
</tr>
</HeaderTemplate>
<ItemTemplate>
<tr>
<td>
<b><%#((MyDTO)Container.DataItem).Name%></b>
</td>
<td>
<asp:ImageButton CausesValidation="false" ID="DeleteData" CommandName="Delete" runat="server" />
<asp:ImageButton CausesValidation="false" ID="RunData" CommandName="Run" runat="server" />
</td>
</tr>
<tr>
<td colspan="2">
<table>
<tr>
<td>Description : </td>
<td><%#((MyDTO)Container.DataItem).Description%></td>
</tr>
<tr>
<td>Search Text : </td>
<td><%#((MyDTO)Container.DataItem).Text%></td>
</tr>
</table>
</td>
</tr>
</ItemTemplate>
</asp:Repeater>
</table>
</ContentTemplate>
</asp:UpdatePanel>
Code-Behind
public DeleteData DeleteDataDelegate;
public RetrieveData PopulateDataDelegate;
public delegate ArrayList RetrieveData();
public delegate void DeleteData(String sData);
protected void Page_Load(object sender, EventArgs e)
{
//load the initial data..
if (!Page.IsPostBack)
{
if (PopulateDataDelegate != null)
{
this.DataRepeater.DataSource = this.PopulateDataDelegate();
this.DataRepeater.DataBind();
}
}
}
protected void DataRepeater_ItemCommand(object source, RepeaterCommandEventArgs e)
{
if (e.CommandName == "Delete")
{
if (DeleteDataDelegate != null)
{
DeleteDataDelegate((String)e.CommandArgument);
BindDataToRepeater();
}
}
else if (e.CommandName == "Run")
{
String sRunning = (String)e.CommandArgument;
this.ViewDataModalPopupExtender.Hide();
}
}
protected void DataRepeater_ItemDataBound(object source, RepeaterItemEventArgs e)
{
RepeaterItem item = e.Item;
if (item != null && item.DataItem != null)
{
MyDTO oQuery = (MyDTO)item.DataItem;
ImageButton oDeleteControl = (ImageButton) item.FindControl("DeleteData");
ImageButton oRunControl = (ImageButton)item.FindControl("RunData");
if (oDeleteControl != null && oRunControl !=null)
{
oRunControl.ImageUrl = "button_expand.gif";
oRunControl.CommandArgument = "MyID";
if (oQuery !=null)
{
//do something
}
oDeleteControl.ImageUrl = "btn_remove.gif";
oDeleteControl.CommandArgument = "MyID";
}
}
}
public void BindDataToRepeater()
{
this.DataRepeater.DataSource = this.PopulateDataDelegate();
this.DataRepeater.DataBind();
}
public void ShowModal(object sender, EventArgs e)
{
BindDataToRepeater();
this.ViewDataModalPopupExtender.Show();
}
Thanks for reminding me why I stopped using ASP.NET controls. This is the exact type of nightmare that has made too many projects go way over budget and schedule.
My advise to you is to think of the simplest way to implement this. You can try to bend over backwards in order to get this to work the ASP.NET way or take the shortest route.
All you're doing is generating HTML, it should never be that difficult.
The most likely cause of your problem is that the ViewState is stored in the page which doesn't get updated on a partial postback. So with every change in the update panel you'll postback the initial viewstate of the page.
Try replacing the repeater with a simple for-loop (and ignore the people who start complaining you shouldn't mix markup and code). Replace your databinding statements with <%= %>.
That eliminates the view state all together and should remove any removed row from re-appearing.
After many days of messing around with this I've not found a proper fix for the problem but do have a workable work-around.
The CollapsiblePanelExtender is set to NOT postback automatically which fixes the issue of the deleted data re-appearing when the extender is opened. The other issue, I believe, is related.
It seems that the ViewState for the Repeater is out of sync with the data. e.CommandArgument is not always correct and seems to reference the previous data. I made an attempt to fix it by storing the ArrayList of MyDTO objects in the ViewState when opening the Modal dialog and using the ID retrieved from e.Item.ItemIndex to find the correct element to delete. This didn't work correctly, the ArrayList pulled out of the ViewState was out of sync.
Storing the ArrayList in the session makes it all work which leads me to believe that I'm doing something fundamentally wrong or there is a subtle bug in the version of the toolkit that i'm using (we're still on VS2005 so are stuck with an older version of the toolkit)
Apologies if this makes no sense, contact me if you want clarification on anything.
try using
((IDataItemContainer)Container).DataItem
instead of "Container.DataItem"
It worked for me.
<%# Register Src="~/Controls/PressFileDownload.ascx" TagName="pfd" TagPrefix="uc1" %>
<asp:Repeater id="Repeater1" runat="Server" OnItemDataBound="RPTLayer_OnItemDataBound">
<ItemTemplate>
<asp:Label ID="LBLHeader" Runat="server" Visible="false"></asp:Label>
<asp:Image ID="IMGThumb" Runat="server" Visible="false"></asp:Image>
<asp:Label ID="LBLBody" Runat="server" class="layerBody"></asp:Label>
<uc1:pfd ID="pfd1" runat="server" ShowContainerName="false" ParentContentTypeId="55" />
<asp:Literal ID="litLayerLinks" runat="server"></asp:Literal>
</ItemTemplate>
</asp:Repeater>
System.Web.UI.WebControls.Label lbl;
System.Web.UI.WebControls.Literal lit;
System.Web.UI.WebControls.Image img;
System.Web.UI.WebControls.HyperLink hl;
System.Web.UI.UserControl uc;
I need to set the ParentItemID variable for the uc1:pdf listed inside the repeater.
I thought I should be able to find uc by looking in the e.Item and then setting it somehow. I think this is the part where I'm missing something.
uc = (UserControl)e.Item.FindControl("pfd1");
if (uc != null) { uc.Attributes["ParentItemID"] = i.ItemID.ToString(); }
Any thoughts would be appreciated.
Also tried this with similar results... when I debug inside my usercontrol (pfd1) the parameters I am trying to set have not been set.
uc = (UserControl)e.Item.FindControl("pfd1");
if (uc != null)
{
uc.Attributes.Add("ContainerID", _cid.ToString());
uc.Attributes.Add("ParentItemId", i.ItemID.ToString());
}
UPDATE: It looks like my controls are not connected by a namespace. I've wrapped by the parent control (Layer) and the PressFileDownlad control in a namespace "MyControls". Also updated their Inherits reference on the aspx to read "MyControls.xxxxx". I'm able to type "MyControls.Layer" inside the code on layer.aspx.cs but I'm not able to get "MyControls.PressFileDownload"
If you implement ParentItemID as a public property in your user control, then you should be able to set it declaratively, e.g:
<asp:Repeater id="Repeater1" ...>
<ItemTemplate>
<uc1:pfd ID="pfd1" runat="server" ParentItemId='<%# Eval("ItemID") %>' ... />
Martin is right you should be able to set it in declarative way (in case your property is public) .
But your way should also work (just cast it properly)
((PressFileDownload)e.Item.FindControl("pfd1")).ParentItemId = 0;
The best way is to implement the OnDataBinding event for the user control. I try to stay away from putting code inline in the aspx using webforms if possible.
When the repeater gets bound, for each item that is bound, the OnDataBinding will fire for your user control and your handler can do what it needs. You don't have to go searching for the controls.
Here is an example:
// in your aspx
<uc1:pfd ID="pfd1" runat="server" ShowContainerName="false" ParentContentTypeId="55"
OnDataBinding="pfd1_DataBinding" />
// in your codebehind implement the OnDataBinding event
protected void pfd1_DataBinding(object sender, System.EventArgs e)
{
pfd uc = (pfd)(sender);
uc.ContainerID = _containerID.ToString();
uc.ParentItemID = Eval("ItemID");
// Here you can do more like access other items like hidden fields
// or cached objects or even other controls etc... Skys the limit.
}
EDIT: Notice from your comment you require more data than what is found in the datasource. In this case what I usually do is just make private member variables in the .cs that I store data in. So when you have the container ID just store it in a variable that will be accessible.
Eg in your .cs for your page:
public partial class _TestPage : System.Web.UI.Page
{
private int _containerID { get; set; }
Then when you load the data just set the _containerID property and it will be accessible in the OnDataBinding event. Just make sure you are binding after you have set the _containerID.
This is a absurdly common issue and having exhausted all of the obvious solutions, I'm hoping SO can offer me some input... I have a UserControl inside a page which contains a repeater housing several controls that cause postback. Trouble is, all of the controls inside of the repeater never hit their event handlers when they postback, but controls outside of the repeater (still in the UC) are correctly handled. I already made sure my controls weren't being regenerated due to a missing if(!IsPostBack) and I verified that Request.Form["__EVENTTARGET"] contained the correct control ID in the Page_Load event. I attempted to reproduce the symptoms in a separate project and it worked as it should.
<%# Control Language="C#" AutoEventWireup="true" CodeBehind="NoteListControl.ascx.cs"
Inherits="SantekGBS.Web.UserControls.NoteListControl" %>
<asp:UpdatePanel ID="upNotes" runat="server" UpdateMode="Conditional">
<ContentTemplate>
<div class="NoteList" id="divNoteList" runat="server">
<asp:Repeater ID="repNotes" runat="server">
<HeaderTemplate>
<table width="98%" cellpadding="3" cellspacing="0">
</HeaderTemplate>
<ItemTemplate>
<tr class="repeaterItemRow">
<asp:ImageButton ID="ImageButton1" runat="server" ImageUrl="~/Content/images/DeleteIcon.gif"
OnClick="ibRemove_Click" CommandArgument='<%# Container.ItemIndex %>' CommandName='<%# Eval("ID") %>'
CausesValidation="false" AlternateText="Delete" />
<%# Eval("Text") %></td>
</tr>
</ItemTemplate>
<FooterTemplate>
</table>
</FooterTemplate>
</asp:Repeater>
<asp:PlaceHolder ID="phNoNotes" runat="server" Visible="false">
<div class="statusMesssage">
No notes to display.
</div>
</asp:PlaceHolder>
</div>
</ContentTemplate>
</asp:UpdatePanel>
public partial class NoteListControl : UserControl
{
[Ninject.Inject]
public IUserManager UserManager { get; set; }
protected List<Note> Notes
{
get
{
if (ViewState["NoteList"] != null)
return (List<Note>)ViewState["NoteList"];
return null;
}
set { ViewState["NoteList"] = value; }
}
public event EventHandler<NoteEventArgs> NoteAdded;
public event EventHandler<NoteEventArgs> NoteDeleted;
public event EventHandler<NoteEventArgs> NoteChanged;
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
UtilityManager.FillPriorityListControl(ddlPriority, false);
}
}
protected void ibRemove_Click(object sender, ImageClickEventArgs e)
{
System.Diagnostics.Debug.WriteLine("ibRemove POSTBACK"); // This is NEVER hit
}
public void Fill(List<Note> notes)
{
Notes = notes;
RefreshRepeater();
}
private void RefreshRepeater()
{
if (Notes != null && Notes.Any())
{
var sorted = Notes.OrderByDescending(n => n.Timestamp);
Notes = new List<Note>();
Notes.AddRange(sorted);
repNotes.Visible = true;
phNoNotes.Visible = false;
repNotes.DataSource = Notes;
repNotes.DataBind();
}
else
{
repNotes.Visible = false;
phNoNotes.Visible = true;
}
}
}
public class NoteEventArgs : EventArgs
{
public Note Note { get; set; }
public NoteEventArgs()
{ }
public NoteEventArgs(Note note)
{
this.Note = note;
}
}
The code is intentionally missing functionality so just disregard that fact.
Your edited code has residual CommandArgument and CommandName properties; are you actually handling the Repeater.ItemCommand event?
If so, and if your page calls the control's Fill method on postbacks, that would explain it.
This classic ASP.NET hair-tearing problem is explained in these posts: A Stumper of an ASP.NET Question and A Stumper of an ASP.NET Question: SOLVED!
The explanation is a little mind-bending, but the crux of it is that Repeater.DataBind interferes with ASP.NET's ability to determine which repeater button caused a postback.
I found a missing td-tag in the Itemtemplate, sometimes when DOM is incorrect, the updatapanel do strange things.
Just about EVERY time I run into this problem it's because DataBind() is being called when it shouldn't be. This will kill most events from controls inside a repeater. I see you have an !IsPostBack check in your Page_Load... so that's a start. But try putting a breakpoint on repNotes.DataBind() and see if it's getting called when you don't expect it.
Does it work OK outside of an UpdatePanel?
I ran into the same problem. It happened with me if I've ran the DataBind twice. In other words when I populate the repeater control twice (for any reason) the events wont fire.
I hope that helps.
Can anyone explain why you can’t use inline code blocks within server control declarations in ASP.Net?
The following is a simple example...
....
<form id="form1" runat="server">
<asp:Label ID="Label1" runat="server" Text="<%= SomeProperty %>"></asp:Label>
</form>
....
The code block is rendered literally to the page...
<span id="Label1"><%= SomeProperty %></span>
My initial thoughts are it has to do with the order that these things are processed in the page life-cycle. The <%=...%> blocks are, as I understand it, equivalent to a Response.Write(...) in code-behind. And since the server control is not actually rendered as declared in the markup, I suppose it may not be possible to process an embedded code block before this rendering takes place.
I would be very grateful of anyone could explain that a little better.
However, the data binding code block <%#...%> is obviously different in the way it behaves, but can anyone tell me why it is possible to embed these within a server control...
....
<asp:Repeater id=Repeater1 runat="server">
....
<ItemTemplate>
<asp:Label ID="Label1" runat="server" Text='<%# Eval(“SomeProperty”) %>'></asp:Label>
</ItemTemplate>
....
</asp:Repeater>
....
This works fine.
You're mostly right about the <%=...%> syntax.
Here is an example of what happens under the hood:
<script runat="server">
public string SomeProperty { get { return "Hello World!"; } }
</script>
<form id="form1" runat="server">
<%= SomeProperty %>
<div>
<asp:Label ID="Label1" runat="server" Text="<%= SomeProperty %>"></asp:Label>
</div>
</form>
This is parsed and the following C# code is created (I've simplified it a bit):
private Label #__BuildControlLabel1()
{
Label #__ctrl = new Label();
this.Label1 = #__ctrl;
#__ctrl.ApplyStyleSheetSkin(this);
#__ctrl.ID = "Label1";
#__ctrl.Text = "<%= SomeProperty %>";
return #__ctrl;
}
private void #__Renderform1(HtmlTextWriter #__w, Control parameterContainer)
{
#__w.Write( SomeProperty );
#__w.Write("\r\n <div>\r\n ");
parameterContainer.Controls[0].RenderControl(#__w);
#__w.Write("\r\n </div>\r\n ");
}
Here is an example of what happens under the hood for the <%#...%> syntax:
<script runat="server">
public string SomeProperty { get { return "Hello World!"; } }
protected void Page_Load(object sender, EventArgs e) { Label1.DataBind(); }
</script>
<form id="form1" runat="server">
<div>
<asp:Label ID="Label1" runat="server" Text="<%# SomeProperty %>"></asp:Label>
</div>
</form>
Generates this code:
private Label #__BuildControlLabel1()
{
Label #__ctrl = new Label();
this.Label1 = #__ctrl;
#__ctrl.ApplyStyleSheetSkin(this);
#__ctrl.ID = "Label1";
#__ctrl.DataBinding += new System.EventHandler(this.#__DataBindingLabel1);
return #__ctrl;
}
public void #__DataBindingLabel1(object sender, EventArgs e)
{
Label dataBindingExpressionBuilderTarget = ((Label)(sender));
Page Container = ((Page)(dataBindingExpressionBuilderTarget.BindingContainer));
dataBindingExpressionBuilderTarget.Text = System.Convert.ToString( SomeProperty , System.Globalization.CultureInfo.CurrentCulture);
}
As you can see the <%=...%> syntax can be used outside of a server control's properties to directly render the returned value. On the other hand the <%#...%> syntax generates a event handler for the DataBinding event of the label. This event sets the value of the label's property to the value of SomeProperty. The DataBinding event fires whenever the DataBind method is called which is why I added that call to the Page_Load event.
Hopefully this will help you understand the difference between them.
You could create a custom ExpressionBuilder so you use something like <%$ Code: SomeProperty %>
You can create a custom databound control, e.g.
namespace FooBar.WebControls
{
public class DataBoundPlaceHolder:PlaceHolder
{
private bool hasDataBound = false;
protected override void CreateChildControls()
{
if (!hasDataBound)
{
this.DataBind();
hasDataBound = true;
}
base.CreateChildControls();
}
}
}
Then wrap your code in this new control, and use the <%# %> syntax, e.g.
<%# Register TagPrefix="WebControls" Namespace="FooBar.WebControls" Assembly="FooBar" %>
<form id="form1" runat="server">
<WebControls:DataBoundPlaceHolder runat="server">
<asp:Label ID="Label1" runat="server" Text='<%# SomeProperty %>'></asp:Label>
</WebControls:DataBoundPlaceHolder>
</form>