HtmlGenericControl（QUOT; BR＆Q​​UOT;）渲染两次

问题描述

我添加从code背后的一些内容，以给定的网页。当我想一些文本后添加一个突破，我尝试这样做，是这样的：

I'm adding some content to a given web page from code behind. When I want to add a break after some text, I try to do that this way:

pDoc.Controls.Add(New Label With {.Text = "whatever"})
pDoc.Controls.Add(New HtmlGenericControl("br"))

，其中PDOC是面板在我添加的内容。但它增加了两个 BR 标记成最终的HTML。

,where pDoc is the Panel in which I'm adding the content. But it adds two br tags into the final HTML.

我已经避免这种情况是这样的：

I've avoid this behaviour this way:

pDoc.Controls.Add(New Label With {.Text = "whatever" & "<br />"})

不过，我很好奇，我想知道为什么。

Anyway, I'm so curious and I want to know why

pDoc.Controls.Add(New HtmlGenericControl("br"))

行事的方式。我也觉得我的做法是不是太花哨。

is acting that way. I also think my approach is not too fancy.

问候，

推荐答案

一些测试它看起来像的原因之后是 HtmlGenericControl 不支持的自动关闭的。在服务器端的 HtmlGenericControl（BR）被视为：

After some testing it looks like the reason is that HtmlGenericControl doesn't support self closing. On server side the HtmlGenericControl("br") is treated as:

<br runat="server"></br>

有没有＆LT; / BR＆gt;在HTML 标签，所以浏览器显示它作为有两个＆LT; BR /＆GT; 标记。尼斯出路是创建 HtmlGenericSelfCloseControl 这样的（对不起，C＃code，但你应该没有问题，在VB.NET rewritting本）：

There is no </br> tag in HTML, so the browser shows it as there are two <br /> tags. Nice way out of this is to create HtmlGenericSelfCloseControl like this (sorry for C# code but you should have no issue with rewritting this in VB.NET):

public class HtmlGenericSelfCloseControl : HtmlGenericControl
{
    public HtmlGenericSelfCloseControl()
        : base()
    {
    }

    public HtmlGenericSelfCloseControl(string tag)
        : base(tag)
    {
    }

    protected override void Render(HtmlTextWriter writer)
    {
        writer.Write(HtmlTextWriter.TagLeftChar + this.TagName);
        Attributes.Render(writer);
        writer.Write(HtmlTextWriter.SelfClosingTagEnd);
    }

    public override ControlCollection Controls
    {
        get { throw new Exception("Self closing tag can't have child controls"); }
    }

    public override string InnerHtml
    {
        get { return String.Empty; }
        set { throw new Exception("Self closing tag can't have inner content"); }
    }

    public override string InnerText
    {
        get { return String.Empty; }
        set { throw new Exception("Self closing tag can't have inner text"); }
    }
}

和使用它来代替：

pDoc.Controls.Add(New Label With {.Text = "whatever"})
pDoc.Controls.Add(New HtmlGenericSelfCloseControl("br"))

作为一个更简单的选择（如果你有参考页），你可以尝试使用 Page.ParseControl ：

As a simpler alternative (if you have reference to the Page) you can try using Page.ParseControl:

pDoc.Controls.Add(New Label With {.Text = "whatever"})
pDoc.Controls.Add(Page.ParseControl("br"))

这篇关于HtmlGenericControl（QUOT; BR＆Q​​UOT;）渲染两次的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！