Invalid postback or callback argument. Event validation is enabled using '<pages enableEventValidation="true"/>'

I am getting the following error when I post back a page from the client-side. I have JavaScript code that modifies an asp:ListBox on the client side.

How do we fix this?

Error details below:

Server Error in '/XXX' Application.

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Invalid postback or callback argument.  Event validation is enabled using <pages enableEventValidation="true"/> in configuration or <%@ Page EnableEventValidation="true" %> in a page.  For security purposes, this feature verifies that arguments to postback or callback events originate from the server control that originally rendered them.  If the data is valid and expected, use the ClientScriptManager.RegisterForEventValidation method in order to register the postback or callback data for validation.
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: Invalid postback or callback argument.  Event validation is enabled using <pages enableEventValidation="true"/> in configuration or <%@ Page EnableEventValidation="true" %> in a page.  For security purposes, this feature verifies that arguments to postback or callback events originate from the server control that originally rendered them.  If the data is valid and expected, use the ClientScriptManager.RegisterForEventValidation method in order to register the postback or callback data for validation.

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: Invalid postback or callback argument.  Event validation is enabled using <pages enableEventValidation="true"/> in configuration or <%@ Page EnableEventValidation="true" %> in a page.  For security purposes, this feature verifies that arguments to postback or callback events originate from the server control that originally rendered them.  If the data is valid and expected, use the ClientScriptManager.RegisterForEventValidation method in order to register the postback or callback data for validation.]
   System.Web.UI.ClientScriptManager.ValidateEvent(String uniqueId, String argument) +2132728
   System.Web.UI.Control.ValidateEvent(String uniqueID, String eventArgument) +108
   System.Web.UI.WebControls.ListBox.LoadPostData(String postDataKey, NameValueCollection postCollection) +274
   System.Web.UI.WebControls.ListBox.System.Web.UI.IPostBackDataHandler.LoadPostData(String postDataKey, NameValueCollection postCollection) +11
   System.Web.UI.Page.ProcessPostData(NameValueCollection postData, Boolean fBeforeLoad) +353
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1194

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Version Information: Microsoft .NET Framework Version:2.0.50727.1433; ASP.NET Version:2.0.50727.1433

The problem is that ASP.NET does not get to know about this extra or removed listitem. You got an number of options (listed below):

• Disable eventvalidation (bad idea, because you lose a little of security that come with very little cost).
• Use ASP.NET Ajax UpdatePanel. (Put the listbox in the Updatepanel and trigger a update, if you add or remove listbox. This way viewstate and related fields get updates and eventvalidation will pass.)
• Forget client-side and use the classic postback and add or remove the listitems server-side.