如果onclick和onselect中的语句在ASP.NET中不起作用

Question

This should be pretty straight forward, but I've been researching for over a day now and can't figure out why this isn't working. 这应该很简单，但是我已经研究了一天多了，无法弄清楚为什么它不起作用。 I'm making a web page in ASP.NET. 我在ASP.NET中制作一个网页。 What I'm trying to do is have a textbox with gray placeholder text that disappears and changes the font color to black when the textbox is clicked or selected. 我想做的是有一个带有灰色占位符文本的文本框，当单击或选择该文本框时，该文本框会消失，并将字体颜色更改为黑色。 Here's my code: 这是我的代码：

<asp:TextBox ID="addEditTextBox1" runat="server" onselect="if(style.color=='#999999'){style.color='Black'; this.value='';}" onclick="if(style.color=='#999999'){style.color='Black';this.value='';}" ForeColor="#999999" Width="250px">Revision #</asp:TextBox>

I've tried changing the "if" statement triggers to 我尝试将“ if”语句触发器更改为

if(style.color.value=='#999999'){...}

and 和

if(ForeColor=='#999999'){...}

and 和

if(ForeColor.value=='#999999'){...}

and many other syntaxes but I can't find one that works. 和许多其他语法，但我找不到一种有效的语法。 I do know the onclick and onselect statements are working because if I replace the "==" with a "=" they trip 100% of the time, but that completely negates the whole idea of an "if" statement. 我确实知道onclick和onselect语句是有效的，因为如果我将“ ==”替换为“ =”，它们会在100％的时间内跳闸，但这完全否定了“ if”语句的整个思想。 I'm new to ASP.NET and JavaScript, so maybe there's something obvious I'm missing, but I can't find it anywhere. 我是ASP.NET和JavaScript的新手，所以也许我缺少一些明显的东西，但是我找不到它。 Here's some other information that I didn't think was relevant but may be helpful: 以下是一些我认为不相关但可能会有所帮助的其他信息：

Running in Visual Studio Professional 2012 在Visual Studio Professional 2012中运行
This is towards the top of the page's source code: 这是页面源代码的顶部：
```
 <html xmlns="http://www.w3.org/1999/xhtml"> 
```
Target Framework: .NET Framework 4.5. 目标框架：.NET Framework 4.5。

Feel free to inquire if I left anything out. 随时询问我是否有遗漏。 Thanks! 谢谢！

Answer 1

Either just simply use a HTML5 placeholder attribute, all the browsers support it now. 只需使用HTML5 placeholder属性，所有浏览器现在都支持它。

Or use this, works for both keyboard tabbing and mouse clicking: 或使用此方法，可同时用于键盘制表键和鼠标单击：

<asp:TextBox ID="addEditTextBox1" runat="server" onfocus="this.onfocus = null; this.value = ''; this.style.color = 'black';" ForeColor="#999999" Width="250px">Revision #</asp:TextBox>

Btw, onclick is really just for buttons, you probably meant onmousedown and onkeydown - onselect is for when selecting text (to prevent it for example). 顺便说一句， onclick实际上仅用于按钮，您可能意味着onmousedown和onkeydown - onselect用于选择文本（例如，防止文本显示）。

如果onclick和onselect中的语句在ASP.NET中不起作用

问题描述

1 个解决方案

解决方案1
0 已采纳 2015-03-10 16:10:31

如果onclick和onselect中的语句在ASP.NET中不起作用

问题描述

1 个解决方案

解决方案1 0 已采纳 2015-03-10 16:10:31

解决方案1
0 已采纳 2015-03-10 16:10:31