在实践中,很少会构建纯粹的组合控件(《ASP.NET2.0揭秘》读书笔记——构建组合控件 ),更多的是构建混合控件,这里说的混合控件指既重写控件的CreateChildControls()方法也重写了RenderContents()方法来指定子控件的布局。
![](https://www.cnblogs.com/Images/OutliningIndicators/ContractedBlock.gif)
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;
}
}
}
}
上面代码重写了Tagkey属性,用table标签包围RenderContents方法输出的HTML内容。另外使用子控件的RenderControl(writer)方法将子控件的内容输出到HtmlTextWriter对象中。