Report rp = new Report();

            rp.Load(@"Print\aa.frx");

            rp.Dictionary.Connections[0].ConnectionString = "5555555";

            rp.Save(@"Print\aa.frx");//是否需要保存，未测试，请自行测试

            rp.Load(@"Print\aa.frx");

            MessageBox.Show(rp.Dictionary.Connections[0].ConnectionString);