why do we not use set or map as a value attribute in pageBlockTable tag in Salesforce?

Hi Yogesh,

You should really keep this type of logic out of a Visualforce page. A Visualforce page should be used simply for View logic.

Apex:-

public Boolean getRenderPageBlockTable(){
    return mapToCheck.containsKey('keyToCheck');
}

Visualforce:-

<apex:pageBlockSection rendered="{!renderPageBlockTable}">
    ...
</apex:pageBlockSection>