Get variable value from code behind and use in aspx page control

Question

I got a web user control where I have controls that needs to be fed with some data from variables or properties from the underlying page.

<%@ Control Language="C#" AutoEventWireup="False" CodeFile="Header.ascx.cs" Inherits="Site.UserControls.Base.Header" %>
<asp:Literal runat="server" Text='<%# Testing %>' id="ltrTesting" />

Codebehind

namespace Site.UserControls.Base
{
    public partial class Header : UserControlBase
    {
        public string Testing = "hello world!";

        protected void Page_Load(object sender, EventArgs e)
        {
            //this.DataBind(); // Does not work
            //PageBase.DataBind(); // Does not work
            //base.DataBind(); // Does not work
            //Page.DataBind(); // Does not work
        }
    }
}

I did read this topic, but it wont solve my problem, I assume it's because this is a user control and not a page. I want to get property value from code behind

Kingmaker

Why not set the value to the controls from code behind instead? – Broomcorn

@Broomcorn Because of portability of the controls, that is of course an option but it's the last option out of this – Kingmaker

The sample above is a simplification of the actual code. The actual usage is that I populate a custom webcontrol with data by sending an entire object to the control. The user controls is standardized in their design and will usually only contain the empty PageLoad method and the object that is to be sent to the webcontrol. Now portability might be the wrong word but due to different reasons we'd prefer to keep it this way, if possible. If not we will go with the code-behind style instead. – Kingmaker

Answer 1

Solved this, solution below

Since I used a web user control in this case the usual scenarios would not work. But by putting a databind in the page that controls the user control, or any materpage in the chain above the web user control the code started to work

MasterPage codebehind

public partial class MasterPages_MyTopMaster : System.Web.UI.MasterPage
{
    protected void Page_Load(object sender, EventArgs e)
    {
        // Databind this to ensure user controls will behave
        this.DataBind();
    }
}

Ascx file, all suggested solutions below works

<%@ Control Language="C#" AutoEventWireup="False" CodeFile="Header.ascx.cs" Inherits="Site.UserControls.Base.Header" %>
1: <asp:Literal runat="server" Text='<%# DataBinder.GetPropertyValue(this, "Testing") %>' />
2: <asp:Literal runat="server" Text='<%# DataBinder.Eval(this, "Testing") %>' />
3: <asp:Literal runat="server" Text='<%# Testing2 %>' />

Codebehind of ascx

namespace Site.UserControls.Base
{
    public partial class Header : UserControlBase //UserControl
    {
        public string Testing { get { return "hello world!"; } }
        public string Testing2 = "hello world!";

        protected void Page_Load(object sender, EventArgs e)
        { }
    }
}

Thanks for the inspiration!

Kingmaker

Answer 2

You can't usually put scriplets in server controls. But there's an easy workaround: use a plain html control:

<span id="ltrTesting"><%= this.Testing %></span>

Jaimiejain

Thats a simple solution but if I let's say want to use a bit more advanced controls like a custom webcontrol that only renders if the value assigned is not null that wont do – Kingmaker

A web control that only renders if a certain value is assigned? That's a whole separate set of issues – Jaimiejain

Adam, that one is already covered and working. If we assign a value to the webcontrol from codebehind everything works fine. But why o why wont it work when accessing the variable values from the aspx page. – Kingmaker

@Trikks - you can't run scriplets in server controls. That's probably why it's not working. – Jaimiejain

Adam, have a look at my own answer, it solves the issue. And my tests to further extend this beyond literals or ASP:controls have been successful. It's awesome :) – Kingmaker

Answer 3

Or you could set the Text property of the Literal in the code behind:

ltrTesting.Text = "Hello World!";

Antediluvian

true, but I do not want to access it from code-behind like that :) – Kingmaker

Answer 4

try making Testing be a property rather than a field:

e.g.

public string Testing
{
    get { return "Hello World!"; }
}

Swinson

Won't make the least difference. – Jaimiejain

sorry but no, that wont change anything – Kingmaker

My excuses, after doing some laborations this turned out to be a part of the solution. +1 for that! – Kingmaker