DataContext.ExecuteQuery<object> returns object {} - sql

Question

I'm trying to write function for selecting optional columns in linq(columns that may not exist). The problem is in linq like this:
using (DataDataContext db = new DataDataContext()){
var collection = from t in table
select new
{
Nonoptional = t.A;
Optional = IsInDB("table","B") ? t.B : -1; //this is optional column
}}
Unfortunately, this won't work because the fragment near Optional will be translated to case statement and error arises that column not exists.
So i decided to "cover" it with function:
using (DataDataContext db = new DataDataContext()){
var collection = from t in table
select new
{
Nonoptional = t.A;
Optional = IsInDB("table","B") ? OptionalColumnValue<int>("table","B","id_table",t.id_table) : -1; //this is optional column
}}
I want this function to be universal. It should work like that" If there is no value or column is nullable and value is null then return default value for type.
I came up with something like this:
//table,column - obvious,id_column - PK column of table, id - id of currently processing record
public static T OptionalColumnValue<T>(string table,string column,string id_columm,int id) T t = default(T);
DataDataContext db = new DataDataContext();
IEnumerable<object> value = db.ExecuteQuery<object>("select " + column + " from " + table + " where " + id_columm + " = " + id.ToString());
List<object> valueList = value.ToList();
if (valueList.Count == 1)//here is the problem
t = (T)valueList.First();
return t;
}
When there is null value db.ExecuteQuery return something like object{}. I'm assuming this is "empty" object,with nothing really in there. I was thinking about checking for "emptiness" of this object( BTW this is not DBull).
When i realised that this is no way either with concrete value in this column(it cannot cast it to return correct type), then I tried db.ExecuteQuery<T>. Then concrete value - OK, null - Exception.
I thought, maybe Nullable<T> as return value. Nop, because string also can be T.
I don't know what to do next. Maybe there's another solution to this problem.