Render、RenderChildren和RenderControl
我们主要研究RenderControl,Render,RenderChildren的执行顺序.
三者的含义从他们的命名可以很清楚的看出.
RenderControl绘制控件
Render绘制
RenderChildren绘制子控件
看下面的代码
public class UserComponent : Control
{
public UserComponent()
{
}
public override void RenderControl(HtmlTextWriter writer)
{
writer.Write(@"<script language='javascript'>alert('RenderControl');</script>");
//base.RenderControl(writer);
}
protected override void Render(HtmlTextWriter writer)
{
writer.Write(@"<script language='javascript'>alert('Render');</script>");
//base.Render(writer);
}
protected override void RenderChildren(HtmlTextWriter writer)
{
writer.Write(@"<script language='javascript'>alert('RenderChildren');</script>");
//base.RenderChildren(writer);
}
}
运行程序:只弹出对话框 RenderControl
说明:最先被调用的是 RenderControl 绘制控件
将base.RenderControl(writer);的注释去掉
public override void RenderControl(HtmlTextWriter writer)
{
writer.Write(@"<script language='javascript'>alert('RenderControl');</script>");
base.RenderControl(writer);
}
运行程序:弹出对话框 RenderControl 然后弹出对话框 Render
说明:控件通过 RenderControl 调用了 Redner
将base.Render(writer);的注释去掉
protected override void Render(HtmlTextWriter writer)
{
writer.Write(@"<script language='javascript'>alert('Render');</script>");
base.Render(writer);
}
运行程序:弹出对话框 RenderControl 然后弹出对话框 Render 然后弹出对话框 RenderChildren
说明:控件通过 RenderControl 调用了 Redner 调用 RenderChildren
现在来看下面的代码,应该有些感觉了吧...
(DesignerSerializationVisibility.Hidden)]，AddAttributesToRender方法
using System;
using System.Web.UI;
namespace WebComponent
{
public class UserComponent : Control
{
public UserComponent()
{
}
public override void RenderControl(HtmlTextWriter writer)
{
//writer.Write(@"<script language='javascript'>alert('RenderControl');</script>");
//base.RenderControl(writer);
if (this.Visible)
{
Render(writer);
}
}
protected override void Render(HtmlTextWriter writer)
{
//writer.Write(@"<script language='javascript'>alert('Render');</script>");
//base.Render(writer);
RenderChildren(writer);
}
protected override void RenderChildren(HtmlTextWriter writer)
{
//writer.Write(@"<script language='javascript'>alert('RenderChildren');</script>");
//base.RenderChildren(writer);
foreach (Control c in this.Controls)
{
c.RenderControl(writer);
}
}
}
}
而在WebControl类下面的Render方法是这样的：
protected internal override void Render(HtmlTextWriter writer)
{
this.RenderBeginTag(writer);
this.RenderContents(writer);
this.RenderEndTag(writer);
}
由于WebControl会输出标签因此在这里Render的重写方法是这样的。
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