As far as I understand your requirements you want to make only one call to the WebService to get the content and not to perform further calls to it. If so, I would like to inform you that we are considering implementing a client event OnClientRequestStart which will be cancelable - in this case you can cancel subsequent calls if they are not needed.
For the time being I prepared for you a workaround - please examine the attached demo. Note, that the workaround overrides an internal method and we do not recommend to have such code - if it is possible for you, please wait until the client event is available (this will be done most probably for the upcoming Q1 2010 release, scheduled for the beginning of March). If, however, you decide to use the workaround for the time being, make sure that you upgrade and remove it once this is possible.
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