《ASP.NET2.0揭秘》讀書筆記——構建混合控制項

在實踐中，很少會構建純粹的群組控制項（《ASP.NET2.0揭秘》讀書筆記——構建群組控制項 ），更多的是構建混合控制項，這裡說的混合控制項指既重寫控制項的CreateChildControls（）方法也重寫了RenderContents（）方法來指定子控制項的布局。

 

Code
using System;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace myControls
{
    public class Login : CompositeControl
    {
        private TextBox txtUserName;
        private TextBox txtPassword;

        public string UserName
        {
            get
            {
                EnsureChildControls();
                return txtUserName.Text;
            }

            set
            {
                EnsureChildControls();
                txtUserName.Text = value;
            }
        }

        public string Password
        {
            get
            {
                EnsureChildControls();
                return txtPassword.Text;
            }

            set
            {
                EnsureChildControls();
                txtPassword.Text = value;
            }
        }

        protected override void CreateChildControls()
        {
            txtUserName = new TextBox();
            txtUserName.ID = "txtUserName";
            this.Controls.Add(txtUserName);

            txtPassword = new TextBox();
            txtPassword.ID = "txtPassword";
            txtPassword.TextMode = TextBoxMode.Password;
            this.Controls.Add(txtPassword);
        }

        protected override void RenderContents(HtmlTextWriter writer)
        {
            writer.RenderBeginTag(HtmlTextWriterTag.Tr);

            // Render UserName Label    
            writer.RenderBeginTag(HtmlTextWriterTag.Td);
            writer.AddAttribute(HtmlTextWriterAttribute.For, txtUserName.ClientID);
            writer.RenderBeginTag(HtmlTextWriterTag.Label);
            writer.Write("User Name:");
            writer.RenderEndTag(); // Label
            writer.RenderEndTag(); // TD
      
            // Render UserName TextBox
            writer.RenderBeginTag(HtmlTextWriterTag.Td);
            txtUserName.RenderControl(writer);
            writer.RenderEndTag(); // TD

            writer.RenderEndTag();
            writer.RenderBeginTag(HtmlTextWriterTag.Tr);

            // Render Password Label    
            writer.RenderBeginTag(HtmlTextWriterTag.Td);
            writer.AddAttribute(HtmlTextWriterAttribute.For, txtPassword.ClientID);
            writer.RenderBeginTag(HtmlTextWriterTag.Label);
            writer.Write("Password:");
            writer.RenderEndTag(); // Label
            writer.RenderEndTag(); // TD

            // Render Password TextBox
            writer.RenderBeginTag(HtmlTextWriterTag.Td);
            txtPassword.RenderControl(writer);
            writer.RenderEndTag(); // TD

            writer.RenderEndTag(); // TR
        }

        protected override HtmlTextWriterTag TagKey
        {
            get
            {
                return HtmlTextWriterTag.Table;
            }
        }

    }
}

上面代碼重寫了Tagkey屬性，用table標籤包圍RenderContents方法輸出的HTML內容。另外使用子控制項的RenderControl(writer)方法將子控制項的內容輸出到HtmlTextWriter對象中。