动态创建的DropDownList没有触发事件。是的，是的AutoPostBack设置为TRUE [英] Dynamically created DropDownList no firing event. yes, Autopostback is set to TRUE

问题描述

下面是我的code为动态的DropDownList。它正确生成HTML。但是，不触发事件。而且，当我改变事件名称为的onchange它给了我一个编译错误说，它无法找到脚本。通过它的存在在我的code-后面。

另外，我在OnInit页面事件添加此。

  pValueCmbBox.Attributes.Add（RUNAT，服务器）;
pValueCmbBox.SelectedIndexChanged + =新的EventHandler（ddlParent_SelectedIndexChanged）;
pValueCmbBox.Attributes.Add（OnSelectedIndexChanged，ddlParent_SelectedIndexChanged）;
pValueCmbBox.Attributes.Add（的AutoPostBack，真）;
 

1. 为什么不OnSelectedIndexChanged被解雇？


2. 是的onchange仅用于调用JavaScript的？


3. 如果我实现这个作为一个ASCX呢？

解决方案

1）它不工作，因为你没有添加属性的AutoPostBack你应该的样子。

  pValueCmbBox.Attributes.Add（RUNAT，服务器）; //没有意义......它只是为了装饰......因为你不能在页面中使用的背后code
pValueCmbBox.SelectedIndexChanged + =新的EventHandler（ddlParent_SelectedIndexChanged）; //这一行也没关系
pValueCmbBox.Attributes.Add（OnSelectedIndexChanged，ddlParent_SelectedIndexChanged）; //这个是没有必要的......因为你已经通过pValueCmbBox.SelectedIndexChanged规定
pValueCmbBox.Attributes.Add（的AutoPostBack，真）; //这就是问题
 

正如你在<一见href=\"http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.dropdownlist_members%28v=VS.71%29.aspx\"相对=nofollow>这里，的SelectedIndexChanged 时发生从岗位之间的列表控件更改服务器的选择。 。所以，你不得不对的AutoPostBack =真个好主意;你应该写：

  pValueCmbBox.AutoPostBack = TRUE;
 

和现在的 =服务器问题，您可以设置的功能背后的页面如下：

 保护无效ddlParent_SelectedIndexChanged（对象发件人，EventArgs的发送）
{
 DropDownList的C =（DropDownList的）寄件人; //这是你pValueCmbBox您设置它的OnInit
 //更多code在这里
}
 

2）的onchange是Javascript，但是对于C＃/ VB可以使用 OnTextChanged 结果
3）您可以做到这一点，因为你已经尝试过......或者我的方式告诉你。 ：）

Below is my code for a dynamic dropdownlist. It does generate the HTML properly. However, the event is not fired. And, when I change the event name to "onchange" it gives me a compile error saying that it couldn't find the script. By it's there in my code-behind.

Also, I'm adding this in the OnInit page event.

pValueCmbBox.Attributes.Add("runat", "server");
pValueCmbBox.SelectedIndexChanged += new EventHandler(ddlParent_SelectedIndexChanged);
pValueCmbBox.Attributes.Add("OnSelectedIndexChanged", "ddlParent_SelectedIndexChanged");
pValueCmbBox.Attributes.Add("AutoPostBack", "True");

1. Why isn't OnSelectedIndexChanged being fired?
2. Is "onchange" only for calling javascript?
3. Should I implement this as an ASCX instead?

解决方案

1) It doesn't work because you're not adding the attribute "AutoPostBack" the way you should.

pValueCmbBox.Attributes.Add("runat", "server"); //doesn't make sense...it's just for decoration...because you can't use in page behind code
pValueCmbBox.SelectedIndexChanged += new EventHandler(ddlParent_SelectedIndexChanged); //this line it's okay
pValueCmbBox.Attributes.Add("OnSelectedIndexChanged", "ddlParent_SelectedIndexChanged"); //this it's not necessary at all...because you already specified through pValueCmbBox.SelectedIndexChanged
pValueCmbBox.Attributes.Add("AutoPostBack", "True"); //this is the problem

As you can see in here, SelectedIndexChanged "Occurs when the selection from the list control changes between posts to the server." . So you had a good idea regarding AutoPostBack = true; You should have written:

pValueCmbBox.AutoPostBack = true;

And now for the runat="server" problem you can set your page behind function as following:

protected void ddlParent_SelectedIndexChanged(object sender, EventArgs e)
{
 DropDownList c = (DropDownList)sender; //this is your pValueCmbBox that you set it in OnInit
 //more code here
}

2) onchange is for javascript, but for c#/vb you can use OnTextChanged
3) You can do that, as you already tried...or the way i told you. :)

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