rectidy this function in mapper

public object Fetch_details(string id34)
{
DataContext db = new DataContext();
var _result=(from r in db.tablename where r.Column1=="ASDF" && r.Column2==1 && r.Column3==id34 select r.column3).SingleOrDefault;
return _result

}

I have written this function in mapper...
Error shown in (var _result) with red underline .My error is
cannot assign method group to implicitly type local variable