Display selected data of selected Contacts

Question

I have a VF Page where I'm displaying list of Contacts as a command link. Once i click on any contact, it redirects me to a new page which displays some data (coming from another object which has a lookup on Contact) of all contacts (This is done). My requirement is once i click on any contact, in the second page, it should only display the data related to selected contact. Thanks in advance.

First Page (List of Contacts)
<apex:form >
    <apex:pageBlock title="Portfolio Services">
        <apex:pageBlockTable value="{!Conlst}" var="C">
        <apex:commandLink action="{!ViewData}">{!C.Name}</apex:commandLink>
        </apex:pageBlockTable>
    </apex:pageBlock>
</apex:form>

Second Page

<apex:form >  
<tr>
<td style="padding-left: 30px"><b><apex:outputText value="Portfolio Details of {!lstContact}"/></b></td>
                    <td></td>

                <tr>

                    <td colspan="2" width="70%">
                       <br/> 
                        <table width="35%">
                            <tr>
                                <td >
                            <apex:commandButton action="{!display}" value="Activity Detail" reRender="ActivityDetailBlock" status="status"/>
                                </td>
                                <td align="right">
                                </td>
                            </tr>
                     <apex:outputPanel id="ActivityDetailBlock" style="width:100%">
                      <apex:pageBlock rendered="{!displayBlock}" id="theBlock">
                        <apex:pageBlockSection title="Activity Details" >
                        <apex:pageBlockSectionItem >
                        <apex:pageBlockTable value="{!listTransaction}" var="trans">
                         <apex:column value="{!trans.Product__c}" width="20%" />
                        <apex:column value="{!trans.Quantity__c}" width="20%"/>
                        <apex:column value="{!trans.Product__r.Price__c}" width="20%"/>
                        <apex:column value="{!trans.Order_Type__c}" width="20%"/>
                        <apex:column value="{!trans.Transaction_Date__c}" width="20%"/>                           
                        </apex:pageBlockTable>
                        </apex:pageBlockSectionItem>
                        </apex:pageBlockSection>
                        </apex:pageBlock>
                        </apex:outputPanel>
                         </td>
                        </tr>
                    </tr>
                 </apex:form> 

Controller

public class Transactionrecordnew { 
public Boolean displayBlock{ get; set; }

public string ClientId{get;set;}
Public String selectedName {get;set;}
public string ProductId{get;set;}    
public List<Contact> lstContact {get; set;}

 public list<Transaction__c >listTransaction{get;set;}
 public list<Transaction__c >listTransaction1{get;set;}
  public Transactionrecordnew()
   {
      getTransaction();
      displayBlock = false;
      Conlst = [select Id,Name, Group__c  from Contact where Group__c='Client'];
     assets=null;
    }
   public void getTransaction()
     {
      listTransaction=new list<Transaction__c >([select name, Account__c, Amount__c,Category__c, Client_ID__c, CMP__c, Gain_Loss__c, Order_Type__c, Product__c,Product_Code__c, Product__r.Price__c, Quantity__c, Transaction_Date__c, Yield__c from Transaction__c]);
   }

     public PageReference display() {
        displayBlock = true;
        return null;
      }

     public PageReference TaxInfo(){


     PageReference reRend = new PageReference('/015/o');
     return reRend;
    }

     public void showTransactions(){
     listTransaction1 =  [Select name, Account__c, Amount__c, Category__c,Client_ID__c,CMP__c, Gain_Loss__c, Order_Type__c, Product__c, Product_Code__c,Product__r.Price__c, Quantity__c, Transaction_Date__c, Yield__c from Transaction__c where Client_ID__c != NULL AND Product__c=: ProductId];  
    }  

   public class cContact{
    public Contact con{get; set;}
    public Boolean selected{get;set;}

    public cContact(Contact c){
        con = c;
        selected = false;
        System.debug('con'+con);
        System.debug('selected'+selected);
       }
    }


public string recid{get;set;}
 public string Client {get;set;}

 public string row{ get; set;}
public list<Contact> Conlst{get;set;}
 Public Contact C;

 public List<Asset> assets {get; set;}

  pagereference ref =new pagereference('/apex/customtable');
 ref.setredirect(true);
 return ref;

}

public PageReference ViewData() {
pagereference ref =new pagereference('/apex/PortfolioDetails');
 ref.setredirect(true);
  return ref;
  }

public void setupAssets()
{
  assets=[select id, Asset_Class__c, Name from Asset where ContactId=:recId];
    }

   public PageReference displayTable() {
    return null;
   }
   }

Answer 1

From what I am reading, you are loading the second page without any reference from the first page.

public PageReference ViewData() {
pagereference ref =new pagereference('/apex/PortfolioDetails');
 ref.setredirect(true);
  return ref;
  }

you probably want to append ?id=XXXXXXXXXXX to the page reference so the controller can read for an ID and look up the contact's transactions that way.