My masterPage, I use acordion menu
<%@ Master Language="C#" AutoEventWireup="true"
CodeBehind="DefaultMaster.Master.cs" Inherits="Lab.DefaultMaster"
ClientIDMode="Static" %>
<%@ Import Namespace="Resources" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<link type="text/css" href="css/style.css" rel="Stylesheet" />
<title>
<asp:ContentPlaceHolder ID="title" runat="server">
</asp:ContentPlaceHolder>
</title>
<link href="css/custom-theme/jquery-ui-1.8.2.custom.css" type="text/css"
rel="Stylesheet" />
<link type="text/css" href="css/accordion.css" rel="Stylesheet" />
<script type="text/javascript" src="/js/jquery-1.4.2.min.js"></script>
<script type="text/javascript" src="/js/jquery-ui-1.8.2.custom.min.js"></script>
<script src="/js/jquery.cookie.js" type="text/javascript"></script>
<script type="text/javascript" src="/js/ddaccordion.js"></script>
<script type="text/javascript">
ddaccordion.init({ //top level headers initialization
headerclass: "expandable", //Shared CSS class name of headers group that are
expandable
contentclass: "categoryitems", //Shared CSS class name of contents group
revealtype: "click", //Reveal content when user clicks or onmouseover the header?
Valid value: "click", "clickgo", or "mouseover"
mouseoverdelay: 200, //if revealtype="mouseover", set delay in milliseconds
before header expands onMouseover
collapseprev: true, //Collapse previous content (so only one open at any time)?
true/false
defaultexpanded: [0], //index of content(s) open by default [index1, index2, etc].
[] denotes no content
onemustopen: false, //Specify whether at least one header should be open always (so
never all headers closed)
animatedefault: false, //Should contents open by default be animated into view?
persiststate: true, //persist state of opened contents within browser session?
toggleclass: ["", "openheader"], //Two CSS classes to be applied to the header when
it's collapsed and expanded,
respectively ["class1", "class2"]
togglehtml: ["prefix", "", ""], //Additional HTML added to the header when it's
collapsed and expanded, respectively
["position", "html1", "html2"] (see docs)
animatespeed: "fast", //speed of animation: integer in milliseconds (ie: 200),
or keywords "fast", "normal", or "slow"
oninit: function (headers, expandedindices) { //custom code to run when headers
have initalized
//do nothing
},
onopenclose: function (header, index, state, isuseractivated) { //custom code to
run whenever a header is opened or closed
//do nothing
}
});
ddaccordion.init({ //2nd level headers initialization
headerclass: "subexpandable", //Shared CSS class name of sub headers group that
are expandable
contentclass: "subcategoryitems", //Shared CSS class name of sub contents group
revealtype: "click", //Reveal content when user clicks or onmouseover the header?
Valid value: "click" or "mouseover
mouseoverdelay: 200, //if revealtype="mouseover", set delay in milliseconds before
header expands onMouseover
collapseprev: true, //Collapse previous content (so only one open at any time)?
true/false
defaultexpanded: [], //index of content(s) open by default [index1, index2, etc]. []
denotes no content
onemustopen: false, //Specify whether at least one header should be open always (so
never all headers closed)
animatedefault: false, //Should contents open by default be animated into view?
persiststate: true, //persist state of opened contents within browser session?
toggleclass: ["opensubheader", "closedsubheader"], //Two CSS classes to be applied
to the header when it's collapsed
and expanded, respectively ["class1", "class2"]
togglehtml: ["none", "", ""], //Additional HTML added to the header when it's
collapsed and expanded, respectively
["position", "html1", "html2"] (see docs)
animatespeed: "fast", //speed of animation: integer in milliseconds (ie: 200),
or keywords "fast", "normal", or "slow"
oninit: function (headers, expandedindices) { //custom code to run when headers
have initalized
//do nothing
},
onopenclose: function (header, index, state, isuseractivated) { //custom code
to run whenever a header is opened or closed
//do nothing
}
});
</script>
<asp:ContentPlaceHolder ID="head" runat="server">
</asp:ContentPlaceHolder>
<style type="text/css">
.style1
{
width: 140px;
}
</style>
</head>
//body
<body style="min-width:930px;">
<table border="0" cellpadding="5" cellspacing="0" width="100%">
<tr>
<td style="vertical-align:top;" class="style1">
<div class="arrowlistmenu">
<h3 class="menuheader expandable">asd</h3>
<ul class="categoryitems">
<li><a href="/GeneralData/Data.aspx">asd</a></li>
</ul>
<h3 class="menuheader expandable">sd</h3>
<ul class="categoryitems">
<li><a href="/Instruct/page2.aspx">sdf</a></li>
<li><a href="/Instruct/page3.aspx">sdf</a></li>
<li><a href="#">sdf</a></li>
<li><a href="#">sdf</a></li>
<li><a href="#">sdf</a></li>
<li><a href="#">sdf</a></li>
</ul>
<h3 class="menuheader expandable">sdf</h3>
<ul class="categoryitems">
<li><a href="#">sdf</a></li>
<li><a href="#">asd</a></li>
<li><a href="#">asd</a></li>
</ul>
<h3 class="menuheader expandable">asd</h3>
</div>
</td></tr></table>
</body>
</html>
when launching a page, he gave me error
Server Error in '/' Application.
An entry with the same key already exists.
Description: An unhandled exception occurred during the execution of the current web
request. Please review the stack trace for more information about the error and where
it originated in the code.
Exception Details: System.ArgumentException: An entry with the same key already exists.
Source Error:
An unhandled exception was generated during the execution of the current web request.
Information regarding the origin and location of the exception can be identified using the exception stack trace below.
Stack Trace:
[ArgumentException: An entry with the same key already exists.]
System.Collections.Specialized.ListDictionary.Add(Object key, Object value)
+6236205
System.Web.UI.ClientScriptManager.RegisterExpandoAttribute(String controlId,
String attributeName, String attributeValue,
Boolean encode) +272
System.Web.UI.ScriptRegistrationManager.RegisterExpandoAttribute(Control control,
String controlId, String attributeName,
String attributeValue, Boolean encode) +115
System.Web.UI.ScriptManager.RegisterExpandoAttribute(Control control, S
tring controlId, String attributeName,
String attributeValue, Boolean encode) +44
You are a lucky to have an error cause in very first rows of your code. Because I'm just horrified by it. Change your validator's ClientIDMode to Predictable.
after 2 hours I found a solution for the following exception .
[ArgumentException: An entry with the same key already exists.]
System.Collections.Specialized.ListDictionary.Add(Object key, Object value) +6888908
System.Web.UI.ClientScriptManager.RegisterExpandoAttribute(String controlId, String attributeName, String attributeValue, Boolean encode) +340
System.Web.UI.ScriptRegistrationManager.RegisterExpandoAttribute(Control control, String controlId, String attributeName, String attributeValue, Boolean encode) +113
in my case it was because selected was true for more than one item in DropDownList Items dictionary
if (DropDown.Items.FindByText(value) != null) {
//important note:
//below line will reset selected true if previously this field is set and caused the exception and must be removed
//DropDown.SelectedIndex = -1;
DropDown.Items.FindByText(value).Selected = true;
}
来源：https://stackoverflow.com/questions/12037182/system-argumentexception-an-entry-with-the-same-key-already-exists