"Pro ASP.NET 3.5 Server Controls and AJAX Components"
Web; using System.Web.UI; using System.Collections.Specialized; using System.ComponentModel; namespace ControlsBook2Lib.Ch05 { [ToolboxData("<{0}:textbox runat=server>"), DefaultProperty("Text")] public class TextBox : Control, IPostBackDataHandler { public string Text { CHAPTER 5 ?– SERVER CONTROL EVEN TS 193 get { object text = ViewState["Text"]; if (text == null) return string.Empty; else return (string)text; } set { ViewState["Text"] = value; } } public bool LoadPostData(string postDataKey, NameValueCollection postCollection) { string postedValue = postCollection[postDataKey]; if (!Text.Equals(postedValue)) { Text = postedValue; return true; } else return false; } public void RaisePostDataChangedEvent() { OnTextChanged(EventArgs.Empty); } protected virtual void OnTextChanged(EventArgs e) { if (TextChanged != null) TextChanged(this, e); } public event EventHandler TextChanged; protected override void Render(HtmlTextWriter writer) { base.Render(writer); Page.VerifyRenderingInServerForm(this); // write out the tag writer.Write("writer.Write(this.UniqueID); writer.Write("\" value=\"" + this.Text + "\" />"); 194 CHAPTER 5 ?– SE RVER CONTROL EVENTS } } } Using the TextBox Control on a Web Form The TextBox web form shown in the Design view in Figure 5-4 hosts the newly minted TextBox control with its TextChanged event capabilities.