简单服务器端控件 Simple Server Control

namespace CustomTextBox
{
    [DefaultProperty("Text")]
    [ToolboxData("<{0}:ServerControl1 runat=server></{0}:ServerControl1>")]
    public class MyTextBox : WebControl,IPostBackDataHandler
    {
        [Bindable(true)]
        [Category("Appearance")]
        [DefaultValue("")]
        [Localizable(true)]
        public string Text
        {
            get
            {
                String s = (String)ViewState["Text"];
                return ((s == null) ? "[" + this.ID + "]" : s);
            }

            set
            {
                ViewState["Text"] = value;
            }
        }

        public MyTextBox()
            : base(HtmlTextWriterTag.Input)
        {
            Text = "";
        }

        protected override void AddAttributesToRender(HtmlTextWriter writer)
        {
            writer.AddAttribute("type", "text");
            writer.AddAttribute("name", this.UniqueID);
            writer.AddAttribute(HtmlTextWriterAttribute.Value, Text);
            writer.AddAttribute("ondblclick", Page.GetPostBackEventReference(this, string.Empty));
            base.AddAttributesToRender(writer);
        }

        protected override void RenderContents(HtmlTextWriter writer)
        {
            base.RenderContents(writer);
        }

        // 返回结果:
        //     如果服务器控件的状态由于回发而发生更改，则为 true；否则为 false。
        public bool LoadPostData(string postDataKey, NameValueCollection postCollection) {
            string postedVal = postCollection[postDataKey];
            string strText = Text;
            if (strText != postedVal)
            {
                Text = postedVal;
                return true;
            }
            return false;
        }


        public event EventHandler TextChanged;

        protected virtual void OnTextChanged( EventArgs e)
        {
            if (TextChanged != null)
            {
                TextChanged(this, e);
            }
        }

        public void RaisePostDataChangedEvent() {
            OnTextChanged( new EventArgs());
        }

    }
}