Share file with Parent Record.

ParentFileSharing.cls

/*
*
* Author : M Hamza Siddiqui
* Description : Share file with Parent Record.
* Last Modified : Oct 1,2019 
*
*/
trigger ParentFileSharing on ContentDocumentLink (before insert) {

    List<ContentDocumentLink> linksToAdd = new List<ContentDocumentLink>();
    Map<String,Set<String>> mapofObject = new Map<String,set<String>>();
    Map<String,String> mapofAcc = new Map<String,String>();
    system.debug(trigger.new.size());
    for(ContentDocumentLink cdl:trigger.new){
        
        if(cdl.LinkedEntityId !=null){
            system.debug('LinkedId ::'+cdl.LinkedEntityId);
            Id myId = cdl.LinkedEntityId;
            Schema.SObjectType sobjectType = myId.getSObjectType();
            String sobjectName = sobjectType.getDescribe().getName();

            if(mapofObject.containsKey(sobjectname)){
                Set<string> ids = mapofObject.get(sobjectname);
                ids.add(myId);
                mapofObject.put((String)sobjectname,ids);
            } else {
                Set<String> ids = new Set<String>();
                ids.add(myId);
                mapofObject.put((String)sobjectname,ids);
            }
        }
    }

    if(mapofObject != null){
        for(String Objname : mapofObject.keySet()){
            set<String> ids = new set<string>();
            ids.addAll(mapofObject.get(Objname));
            if(Objname=='Contact'){
                String Query = 'Select Id,AccountId From ' + Objname + ' Where Id In :ids';
                system.debug('Query=='+Query);
                for(SObject record : Database.query(Query)){
                    mapofAcc.put((String)record.get('Id'),(String)record.get('AccountId'));
                }
            }
        }
    }

    for(ContentDocumentLink cdl:trigger.new){  
        if (mapofAcc != null) { 
            // Sharing File with Account
            linksToAdd.add(new ContentDocumentLink(ContentDocumentId=cdl.ContentDocumentId,
                                                    LinkedEntityId=mapofAcc.get(cdl.LinkedEntityId),
                                                    ShareType='C')
            );
        }
    }
    system.debug('size=='+linksToAdd.size());
    // DML Operation
    if(linksToAdd.size() != null)
    insert linksToAdd;
}