ASP.NET

using System;<br />
using System.Collections.Generic;<br />
using System.ComponentModel;<br />
using System.Linq;<br />
using System.Text;<br />
using System.Web;<br />
using System.Web.UI;<br />
using System.Web.UI.WebControls;<br />
<br />
namespace TestControl<br />
{<br />
    [DefaultProperty("Text")]<br />
    [ToolboxData("<{0}:PersistText runat=server>")]<br />
    public class PersistText : WebControl<br />
    {<br />
        Panel pnl = new Panel();<br />
<br />
        [Bindable(true)]<br />
        [Category("Appearance")]<br />
        [DefaultValue("")]<br />
        [Localizable(true)]<br />
        public string Text<br />
        {<br />
            get<br />
            {<br />
                String s = (String)ViewState["Text"];<br />
                return ((s == null) ? String.Empty : s);<br />
            }<br />
<br />
            set<br />
            {<br />
                ViewState["Text"] = value;<br />
            }<br />
        }<br />
<br />
        protected override void CreateChildControls()<br />
        {<br />
            TextBox txtBox = new TextBox();<br />
            txtBox.ID = "myTextBox";<br />
            pnl.Controls.Add(txtBox);<br />
            Button btn = new Button();<br />
            btn.Text = "Assign";<br />
            btn.Attributes.Add("onclick", "document.getElementById('" + txtBox.ClientID + "').value = 'my value'; alert('Value Set!');");<br />
            pnl.Controls.Add(btn);<br />
        }<br />
<br />
        protected override void RenderContents(HtmlTextWriter output)<br />
        {<br />
            AddAttributesToRender(output);<br />
            pnl.RenderControl(output);<br />
        }<br />
    }<br />
}