Two-way binding of string property to TextBox in ASP.NET WebForms

Question

I am trying to implement the simplest possible (so it seemed to me) databinding of a TextBox to a property of the page, except the databinding is supposed to be two-way, so instead of <%# Test %>, I use <%# Bind("Test") %>. (Actually, the goal is to have a single object as a property and to bind to its properties, but let's start from something simple.) I am testing it on this simple code:

TestForm.aspx

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:TextBox ID="TestTextBox" runat="server" Text='<%# Bind("Test") %>' />
    </div>
    </form>
</body>
</html>

TestForm.aspx.cs:

using System;

namespace WebApplication1
{
    public partial class TestForm : System.Web.UI.Page
    {
        public string Test { get; set; }

        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                Test = "Hello";
            }
        }

        protected override void OnPreRender(EventArgs e)
        {
            base.OnPreRender(e);
            DataBind();
        }
    }
}

The call of DataBind() results in an InvalidOperationException: Databinding methods such as Eval(), XPath(), and Bind() can only be used in the context of a databound control.

What is wrong with this approach?

Reg Edit · Accepted Answer · 2014-08-27 19:23:02Z

1

Sadly, Eval and Bind can only be used in conjunction with a databound control such as a grid. This is because they expect to be executed within a naming container that has a current data item, such as the selected row in a grid.

So you can use that syntax to bind to a textbox that's located within a grid row template or suchlike, but not a textbox out on its own.

answered Aug 27, 2014 at 19:23

Reg Edit

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Comments

Rajnikant · Accepted Answer · 2014-10-08 12:25:08Z

0

You should be using any one of

Microsoft.Ajax library which has two way data binding support.
1. Knockout Js (Mv* style, supports two way binding)
2. Angular Js (MV* style, supports two way binding)

using above framework you can retrieve json object and bind that directly to any of html element or attribute.

answered Oct 8, 2014 at 12:25

Rajnikant

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