Question

I have a webcontrol with two dropdownlists on in. When you choose something from the first, the second is populated accordingly. When post back occurs I get the old:

Invalid postback or callback argument. Event validation is enabled
using 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.

I know what this problem is; I am populating the dropdown with unexpected data. I’ve read up on the error and found fixes like overriding the Render method where you call “RegisterForEventValidation” for each new dropdownlist item. I can’t do this, however, as I am repopulating the dropdown client side.

In theory I could use this method if I added every possible value (around 3000) that could be included in the dropdown, but I didn’t really want to do this.

Are there any other ways of getting around this error, without disabling EventValidation or populating the dropdownlist server side?

Answer 1

You might have to use a basic html select and look for the selected value on the Request.Form collection.

With the DropdownList I’m afraid you have no other option but those 2.