How to filter based on ContactID

How to filter based on ContactID

Has anyone tried to use getSearchRecords and ContactID as the search condition? 

string url = "https://crm.zoho.com/crm/private/xml/Cases/getSearchRecords?ticket=" + Ticket + "&apikey=" + APIKey + "&selectColumns=All" + "&searchCondition=(CONTACTID|=|" + ZohoCONTACTID + ")";
It doesn't work for me.
I get back this
<?xml version="1.0" encoding="UTF-8" ?> <response uri="/crm/private/xml/Cases/getSearchRecords"><error><code>4832</code><message>Invalid parameter value</message></error></response>