Your query is vulnerable for a security issue called SQL injection!
You should NEVER use string concatenation for building a query from strings (some SQL, some parameters)... Use always parameterized queries...
Sample code:
comm.BindByName = true;
comm.CommandText = "SELECT * FROM ZAEDBA WHERE USER_ID = :login_id AND APPID = :app_id";
comm.Parameters.AddWithValue ("login_id", login_id);
comm.Parameters.AddWithValue ("app_id", app_id);