How to show a pageblockSectionItem depending on certain value selected from a selectlist?

Question

On visualforce page I have a selectlist. If A, B , or C is selected. I want to show the second pageBlockSectionItem. If it's not one of those values I want to show the first pageBlockSectionItem section.

The problem I am having is when I select A the second pageblockSectionItem shows, but it doesn't show if I select B or C.

I would like the second pageblockSectionItem section to show also if A, B or C is selected It seems to only work correctly if A is selected only.

VisualForce

<apex:actionFunction name="manageType2" action="{!manageType}" 
rerender="pbSecCharges" status="typeStatus" immediate="true">
    <apex:param name="dealType" value="" assignTo{!SelectedType}"/>
</apex:actionFunction>

<apex:selectList value="{!Opty.Deal_Rent__c}" required="true"  
 id="ddlRentType" onchange="manageType(this);" size="1" >
    <apex:selectoption itemLabel="A" itemValue="A"></apex:selectoption>
    <apex:selectoption itemLabel="B" itemValue="B"></apex:selectoption>
    <apex:selectoption itemLabel="C" itemValue="C"></apex:selectoption>
    <apex:selectoption itemLabel="D" itemValue="D"></apex:selectoption>
</apex:selectList>

<apex:pageBlockSectionItem rendered="{!Show}" id="itemRealEstate">
   <apex:inputField value="{!Opty.Permanent_Tax__c}" id="txtRealEstate" 
    required="true" />
   <apex:inputField value="{!Opty.Permanent_Tax_Notes__c}"/>
</apex:pageBlockSectionItem>

<apex:pageBlockSectionItem   rendered="{!!Show}">
     <apex:outputLabel value="$0.00"/>
     <apex:inputField value="{!Opty.Permanent_Tax_Notes__c}"/>
   </apex:pageBlockSectionItem>

Apex Class

public class RentExtension{
public string SelectedType {get;set;}
public Boolean Show {get;set;}    

public void manageType() {
Show = show(SelectedType);
}

private static boolean show(string dealType) {
boolean show = false;
 if(dealType != null){ 
    show = (dealType != Utility.DEAL_A || dealType != Utility.DEAL_B 
             ||dealType != Utility.DEAL_C);
}
return show;        
}

Answer 1

When you select ModifiedGross or Standard the expression showRealEstateTax = (dealRentType != Utility.DEAL_GROSS || dealRentType != Utility.DEAL_MODIFIEDGROSS || dealRentType != Utility.DEAL_STANDARD); evaluates to true.

And in your VF page, you have used rendered="{!!ShowRealEstate}" to show the second-page block section.

So when you select ModifiedGross or Standard ShowRealEstate becomes true and the expression {!!ShowRealEstate} evaluates to false and the apex:pageBlockSectionItem doesn't render.