如何使用密码保护* .sdf（sqlCE文件）

if (!File.Exists(SDK))
            {
                    SqlCeEngine engine = new SqlCeEngine(\"Data Source=\" + SDK + \"; Case Sensitive=True\"); 
                    engine.CreateDatabase();
                   OpenConn();
                    SqlCeCommand CMD = new SqlCeCommand();
                    CMD = Conn.CreateCommand();
                    CMD.CommandText = \"Create table MEN(Code int ,Fname nvarchar(50),Lname nvarchar(50))\";
                    CMD.ExecuteNonQuery();
                }