I have modified the code as below referred from StackOverflow
indexlist = (from item in indexlist
where ContainsIgnoreCase(item.restaurant_location,searchtext)
|| ContainsIgnoreCase(item.restaurant_name, searchtext)
|| ContainsIgnoreCase(item.cuisine_type, searchtext)
|| ContainsIgnoreCase(item.special_dishes, searchtext)
select item).ToList();
placelist = (from item in placelist
where ContainsIgnoreCase(item.category_name, postData)
|| ContainsIgnoreCase(item.category_tags, postData)
|| ContainsIgnoreCase(item.category_address, postData)
select item).ToList();
eventlist = (from item in eventlist
where ContainsIgnoreCase(item.event_name, searchconte)
|| ContainsIgnoreCase(item.event_location, searchconte)
select item).ToList();
othersList = (from item in othersList
where ContainsIgnoreCase(item.category_name, PostData)
|| ContainsIgnoreCase(item.category_tags, PostData)
|| ContainsIgnoreCase(item.category_address, PostData)
select item).ToList();
This modification worked for me,
Thank You for trying out my problem.