Inserting composite row using fluent cassandra api

Question

I created a composite primary key column family in cassandra

CREATE TABLE rMessage ( Key varchar,msg_id varchar, msg blob, PRIMARY KEY(key,msg_id) );

I am trying to create a record via Fluent cassandra api.

       string key = "cat1"; 
       string id = "2";

       CompositeType compositeKey = new CompositeType<FluentCassandra.Types.AsciiType, FluentCassandra.Types.AsciiType>(key,id);
       FluentColumnFamily record = ColumnFamily.CreateRecord(compositeKey.ToString());
       dynamic r = record.AsDynamic();
       r.msg = blob;
       record.Columns[0].ColumnTimeUntilDeleted = diff;
       Context.Attach(record);                
       Context.SaveChanges();

The above code return error "Not enough bytes to read value of component 0". I couldn't figure out why.

I tried the below approach but still getting the same error "Not enough bytes to read value of component 0".

var blob = CassandraBinaryFormatter.Serialzie(value);
            var compositeKey = new CompositeType<FluentCassandra.Types.UTF8Type, FluentCassandra.Types.UTF8Type>(key, value.ID.ToString());
            FluentColumnFamily record = ColumnFamily.CreateRecord(key); 
            record[compositeKey.ToString()] = blob;
            Context.Attach(record);
            Context.SaveChanges();

Thanks for help.