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Is there an ASP.NET databindable control (like Repeater), which only expects a single item?

I'm trying display lots of properties from a business object on a Web Form. I could of course, create loads of labels and assign all the values in code-behind, but I feel there must be a less verbose way.
What I want is something like an asp:Panel but where you can specify a datasource. It doesn't seem like Panels support any kind of databinding.
What I'd like is something like this
// C#
panel.DataSource = theCompany;
panel.DataBind();
Then:
// ASPX
<asp:Panel runat="server">
Name: <%# Eval("Name") %>
Phone: <%# Eval("Phone") %>
...
</asp:Panel>
..but I can't find anything which will allow me to work in this way.
I thought I might be able to use asp:FormView but this just gives the error "Data source is an invalid type. It must be either an IListSource, IEnumerable, or IDataSource."
A caveat is that I do not want to call a global DataBind() (this has caused us no-end of problems in the past) - I would like the databind to be constrained to a particular part of the page.

It seems you can do this using a Panel, but you have to assign your business object to a page property first, as there's no way to set the business object as a "DataSource" for the panel (as you would for a Repeater control, for instance).
Once the object is assigned as a page property, you can then use the following syntax in the .aspx to access the properties of that object, without needing to manually assign each item to control values in code behind:
<%# Company.Name %>

You don't need to databind (although you can). What you need is a simple expression evaluator. Add a property to your code behind like this
public string Test { get; set; }
protected void Page_Load(object sender, EventArgs e)
{
Test = "<script>alert('test');</script>";
}
Then use it to render code directly to the page like this
The value: <%: Test %>
Note that the <%: syntax escapes the input. If you wish to NOT escape the input then you can use <%= syntax. Note that you don't need to have a string object you can access any properties you like for example
The value lenght: <%: Test.Length %>

Use The below:
<asp:DetailsView runat="server">
Name: <%# Eval("Name") %>
Phone: <%# Eval("Phone") %>
</asp:DetailsView>

Use DetailsView. You can add it from the Toolbox. It's for Single Row Data Presentation.
<asp:DetailsView runat="server">
Name: <%# Eval("Name") %>
Phone: <%# Eval("Phone") %>
</asp:DetailsView>

Why not using DetailsView. Its perfect for what you want. Showing single row of data only and that too in two column form.

I suggest using a standard Repeater, databound with an array containing a single item.
Repeater.DataSource = new [] { theCompany };
Repeater.DataBind();
Advantage over databinding to a Panel: you can still use the ItemType attribute, and have access to the nice strongly typed Item object and don't have to go about using Eval, i.e.:
<asp:Repeater runat="server" Id="Repeater" ItemType="CompanyViewModel">
<ItemTemplate>
Name: <%# Item.Name %>
Phone: <%# Item.Phone %>
</ItemTemplate>
</asp:Repeater>
(Replace "CompanyViewModel" with the Type of your: "theCompany".)
You can also try experimenting with DetailsView, but it's not as malleable as a Repeater.

Create your own user control that shows the properties of the objects. You can use reflection to read property names and values and display in control.
Create a property for your object in your user control. Inside user control code behind write function Show() with below code.
//Build html strin from all propeties
PropertyInfo[] properties = yourObject.GetType().GetProperties();
string lbl = "<label>{0}</label>";
string value= "<span>{0}</span>";
string tab ="\t";
StringBuilder sb = new StringBuilder();
foreach (PropertyInfo pi in properties)
{
var label = string.Format(lbl,pi.Name);
var val = string.Format(value, pi.GetValue(yourObject, null))
sb.Append(label+tab+val);
sb.Append("<br/>")
}
Response.Write(sb.ToString());
Now in your pager add that control and sets its object property in code behind like
myControl.MyObject = yourObject;
myControl.Show();

NickG's answer will work... however consider two scenarios.
If your business object is ever null, the page will crash with an "Object Reference" error. This can be avoided with a cumbersome looking
<% if(MyObject != null) { %><%= MyObject.Prop %><% } %>
... but doing that every time makes for messy code.
If your page uses PostBack processing via UpdatePanel, the business object will have to be reloaded to the property every time the Page lifecycle runs... even if that portion of the page isn't being redrawn. This is because IIS will resolve all the <%= MyObject.Prop %> references regardless, causing wasted CPU cycles and probably wasted database calls if your object is coming from a database.
For these reasons I always use a Repeater control, which is lightweight, supports ViewState, can easily be assigned a one item list, and avoids the aforementioned issues. Here's an example using the HttpContext.Current.Request object as a "business object".
<asp:Repeater ID="rptTest" runat="server">
<ItemTemplate>
Request.URL = <%# Eval("Url") %>
</ItemTemplate>
</asp:Repeater>
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
var objTest = Request; //Using the Request object as a test business object
rptTest.DataSource = new List<System.Web.HttpRequest>() { objTest };
rptTest.DataBind();
}
}

To make this work we can customize ASP.NET Panel by inheriting it and using Custom Server control for ASP.NET
Use Below Code to modify the ASP.NET Panel in an ASP.NET Custom Server Control Project:
[DefaultProperty("Text")]
[ToolboxData("<{0}:CustomPanel runat=server></{0}:CustomPanel>")]
public class CustomPanel : Panel
{
[Bindable(true)]
public object MyDataSource
{
get;
set;
}
[Bindable(true)]
[Category("Appearance")]
[DefaultValue("")]
[Localizable(true)]
public StringBuilder Text
{
get;
set;
}
public void MyDataBind()
{
Text = new StringBuilder();
foreach (PropertyInfo p in MyDataSource.GetType().GetProperties())
{
Text.Append(string.Format("<b>{0}</b>", p.Name));
Text.Append(":");
if (p.GetIndexParameters() == null || p.GetIndexParameters().Length == 0)
Text.Append(p.GetValue(MyDataSource, null));
Text.Append("<br />");
}
}
protected override void RenderContents(HtmlTextWriter output)
{
output.Write(Text);
}
}
Then add this control's reference and toolbox item to your ASP.NET page:
<cc2:CustomPanel ID="MyCustomPanel" runat="server">
</cc2:CustomPanel>
Use the control as shown below:
MyCustomPanel.MyDataSource = theCompany;
MyCustomPanel.MyDataBind();

NullReferenceException when assigning a Session variable/value

I have in many places in my ASP.NET project used the Session variable for storing data. I usually write something like this:
public uint MyPropery
{
get
{
object o = Session["MyProperty"];
if (o != null)
return (uint)o;
else
return 0;
}
set
{
Session["MyProperty"] = value;
}
}
However, this time I get a NullReferenceException in the setter. As far as I know, it is valid to assign the Session variable in the manner above. Also, Session is not null and neither is value.
Any ideas on this?
Edit:
Adding the code for the UserControl in which the property exists. I am using ext.net but that shouldn't have anything to do with this. One thought that crossed my mind:
The UserControl (seen below) is added dynamically in code-behind of a page. Can that have anything to do with it?
I am adding UserControls like this (on a Page):
foreach(CoreCommons.System.Comment c in cg.Reply_Comments)
{
WebApplicationExtNetTest.Secure.UserControls.CoreComment cc = new UserControls.CoreComment();
cc._Comment = c; // here is where i get the NullRef
this.Panel1.ContentControls.Add(cc);
}
Markup:
<%# Control Language="C#" AutoEventWireup="true" CodeBehind="CoreComment.ascx.cs" Inherits="WebApplicationExtNetTest.Secure.UserControls.CoreComment" %>
<%# Register Assembly="Ext.Net" Namespace="Ext.Net" TagPrefix="ext" %>
<ext:Panel runat="server" ID="CoreCommentOuterPanel" BodyStyle="background: #FFFDDE">
<Items>
<ext:ColumnLayout runat="server">
<Columns>
<ext:LayoutColumn ColumnWidth="0.8">
<ext:Image runat="server" ImageUrl="/Resources/bullet_triangle_green_16x16.png" Align="AbsMiddle"></ext:Image>
<ext:Label runat="server" ID="lblCommentInfo"></ext:Label>
</ext:LayoutColumn>
<ext:LayoutColumn ColumnWidth="0.2"><ext:Button runat="server" ID="btnDelete" Icon="Delete"></ext:Button></ext:LayoutColumn>
</Columns>
</ext:ColumnLayout>
<ext:Label runat="server" ID="lblComment"></ext:Label>
</Items>
</ext:Panel>
Code-behind:
namespace WebApplicationExtNetTest.Secure.UserControls
{
public partial class CoreComment : System.Web.UI.UserControl
{
public CoreCommons.System.Comment _Comment
{
get
{
object o = Session["CoreComment_ObjectId"];
if (o != null)
return (tWorks.Core.CoreCommons.System.Comment)o;
else
return null;
}
set
{
Session["CoreComment_ObjectId"] = value;
SetComment();
}
}
protected void Page_Load(object sender, EventArgs e)
{
}
private void SetComment()
{
if (_Comment == null)
{
lblCommentInfo.Text = "";
lblComment.Text = "";
}
else
{
lblCommentInfo.Text = _Comment.Author + ", " + _Comment.TimeStamp.ToString("g");
lblComment.Text = _Comment.Text;
}
}
}
}

I'm almost completely sure the NullReferenceException is thrown in SetComment() because none of the CoreComment's child controls (lblComment, lblCommentInfo) are properly instantiated at the point you set the _Comment property.
The reason these child controls are not instantiated is indeed the way you currently add the CoreComment controls. For dynamically adding UserControls, you must use Page.LoadControl() (see: here) to create a new instance of the control, as it does some behind-the-scenes magic to ensure it is properly initialized, which includes the instantiation of the child controls.
On a sidenote, personally I'd change SetComment() to SetComment(CoreCommons.System.Comment comment) and use the parameter instead of repeatedly calling the getter, or, if staying with the original, at least call the getter only once and store the result in a local variable. With what I assume is probably InProc session storage it won't make much of a difference, but in any other storage mode you'd repeatedly deserialize the Comment object for no reason.

You need to use the Page.LoadControl() method instead , please look here
BTW:the problem is in adding the control programatically with that way.

Use:
return Session["MyProperty"] as uint? ?? 0;
and post somewhere full exception stack trace with inner exception(s)

How to display a list of user controls in ASP.NET WebForms

This is not really a question so I hope don't be fired!
So I have to make a twitter like timeline, a superposition of blocks containing informations.
I really don't know how to make this.. The problem is the number of blocks aren't the same each time, sometimes it will be 1 block only, sometimes two or sometimes more..
So do I make some HtmlWriter to write the html directly? I pretty new in asp.net so maybe it is possible to do that more easily! With WebUserControl maybe, a block = a wuc so I can add the number of wuc I need.. I'm quite lost so maybe somebody have done this kind of thing already and can put me on the right way..
Thank you for reading!

You are on a right track with creating a usercontrol to represent a "block", but what you're lacking is a mechanism to show them as a list.
ASP.NET has many possible solutions for this, but the simplest one would be to use a ListView control.
It's hard to provide example code without knowing what your data looks like, but let's assume you have a class called Block:
public class Block
{
public string Title {get; set;}
public string Text { get; set; }
}
To display one block, you would create a user control, let's call it BlockControl:
Markup:
<div style="margin:10px; padding:10px; background:#eee;">
<h2><%= Block.Title %></h2>
<%= Block.Text %>
</div>
Code-behind:
public partial class BlockControl : System.Web.UI.UserControl
{
//Note the public property, we'll use this to data bind the ListView's item to the user control
public Block Block { get; set; }
protected void Page_Load(object sender, EventArgs e)
{
}
}
Then, in your .aspx page you can declare an ASP.NET ListView control, and use BlockControl in the ListView's ItemTemplate to present the data. Notice how we bind the ListView's current data item to the BlockControl.Block property.
<asp:ListView ID="BlockList" runat="server">
<ItemTemplate>
<uc:BlockControl Block="<%# Container.DataItem %>" runat="server" />
</ItemTemplate>
</asp:ListView>
From the .aspx code-behind you set the ListView data source. In your case the data probably comes from a database, but here it's just some mock data:
protected void Page_Load(object sender, EventArgs e)
{
List<Block> blocks = new List<Block>
{
new Block { Title = "Block1", Text="This is the block 1 content"},
new Block { Title = "Block2", Text="This is the block 2 content"}
};
this.BlockList.DataSource = blocks;
this.BlockList.DataBind();
}
Now you have the presentation of a single block encapsulated in a user control, and the ListView provides you with the mechanism to display a variable number of these user controls based on your data.

Adding an ASP.NET Web User Control to a Control Dynamically

I have a simple ASP.NET Web User Control. It looks like this:
<%# Control Language="C#" AutoEventWireup="true"
CodeBehind="NewsArticle.ascx.cs"
Inherits="Website.Controls.NewsArticle" %>
<div>
<asp:Literal ID="ltlBody" runat="server" />
</div>
My code behind looks like this:
namespace Website.Controls
{
public partial class NewsArticle : System.Web.UI.UserControl
{
public String bodyText
{
//get { return ltlBody.Text; }
set { ltlBody.Text = value; }
}
}
}
On a .aspx page I have <asp:Panel ID="pNews" runat="server" />
In the code behind I have:
foreach (vwNews news in newsQuery)
{
NewsArticle article = new NewsArticle();
article.bodyText = news.Body;
pNews.Controls.Add(article);
}
Every time I run this code the newsQuery is populated correctly and I get to the line
aticle.bodyText = news.Body; and then I received the error article.bodyText threw an exception of type 'System.NullReferenceException'
I am not sure what is causing this error message or how to fix it. I would think that there should not be an issue. I tried creating a constructor for my Web User Control so that it would give default values to my properties but that didn't work. Any idea how to make this work? It doesn't seem like it should be that

To load a control programatically you need to use the Page.LoadControl() method. See this MSDN article

You have a typo within the code you've written. 'aticle' instead of 'article'.

How do I declare a C# Web User Control but stop it from initializing?

I have a C#/ASP.NET .aspx page that declares two controls that each represents the content of one tab. I want a query string argument (e.g., ?tab=1) to determine which of the two controls is activated. My problem is, they both go through the initialization events and populate their child controls, wasting CPU resources and slowing the response time. Is it possible to deactivate them somehow so they don't go through any initialization?
My .aspx page looks like this:
<% if (TabId == 0)
{ %>
<my:usercontroltabone id="ctrl1" runat="server" />
<% }
else if (TabId == 1)
{ %>
<my:usercontroltabtwo id="ctrl2" runat="server" />
<% } %>
And that part works fine. I assumed the that <%'s would have meant the control wouldn't actually be declared and so wouldn't initialize, but that isn't so...

If inline/spaghetti server side code does not help, I can only think of one alternative solution: avoid declaring the controls in the markup. Instead, load the control you actually want on the page from your Page_Init event handler. The Page.LoadControl() method can be used for this:
void Page_Init(object sender, System.EventArgs e)
{
Control tab;
switch (TabId)
{
case 0: tab = LoadControl("usercontroltabone.ascx"); break;
case 1: tab = LoadControl("usercontroltabtwo.ascx"); break;
default: tab = LoadControl("defaulttab.ascx"); break;
}
somePlaceholder.Controls.Add(tab);
}

move the initialization code out of the .Load and into your own custom public method, and call the initiator explicitly when appropriate.

Apply your logic in the codebehind.
Declare the control:
<my:usercontroltabtwo id="ctrl2" Visible="False" runat="server" />
And then set the Visibility:
if(TabId == 0)
{
ctrl1.Visible = true;
}
else if(TabId == 1)
{
ctrl2.Visible = true;
}

UserControl.dispose() method stop usercontrol page_load event to fire.