请教关于下面这段代码，这是我在一个事件触发函数中写的，databaseip,databasename,dbpw,databasepsaaword,Uname,Unamedb,Upassword都为预定义好的全局String变量，我这段代码的意图是通过用户输入的sqlserver ip地址和sqlserver用户名，密码，来重新连接数据库。通过输入的当前操作用户的用户名和密码，来检验操作员的密码是否正确。这段代码编译没有什么问题，可执行这后做相应的操作便会有一大堆错误？请教高手！这该如何解决？
       char[] dbpw;
       char[] oppw;
       databaseip = jTextField36.getText();
       databasename = jTextField37.getText();
       dbpw = jPasswordField15.getPassword();
       databasepassword = dbpw.toString();
       Uname = jTextField38.getText();
       Unamedb = "'" + Uname + "'";
       oppw = jPasswordField16.getPassword();
       Upassword = oppw.toString();
       database = "jdbc:microsoft:sqlserver://" + databaseip + ":1433;DatabaseName=Bank";
       database1.setConnection(new com.borland.dx.sql.dataset.ConnectionDescriptor(database, databasename, databasepassword, false, "com.microsoft.jdbc.sqlserver.SQLServerDriver"));
       if (Upassword  != null)
       {
             String sqlres=null;
             sqlstatement = "SELECT U_Password FROM Userinfo WHERE UID = " + Uname;
             queryDataSet1.close();
             queryDataSet1.setQuery(new com.borland.dx.sql.dataset.QueryDescriptor(database1, sqlstatement, null, true, Load.ALL));
             sqlres = queryDataSet1.getString(0);
             if (!sqlres.equals(Upassword))
             {
                  JOptionPane.showMessageDialog(jOptionPane1, "操作密码错误！请重新输入！",
                        "错误", JOptionPane.ERROR_MESSAGE);
             }

       }

错误提示
See com.borland.dx.dataset.DataSetException error code:  BASE+42

com.borland.dx.dataset.DataSetException: Operation failed.  DataSet is not open.

at com.borland.dx.dataset.DataSetException.a(Unknown Source)

at com.borland.dx.dataset.DataSetException.dataSetNotOpen(Unknown Source)

at com.borland.dx.dataset.DataSet.getVariantStorage(Unknown Source)

at com.borland.dx.dataset.ReadRow.getString(Unknown Source)

at com.seu.bank.admin.Main.jButton32_actionPerformed(Main.java:1183)

at com.seu.bank.admin.Main$29.actionPerformed(Main.java:702)

at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1764)

at javax.swing.AbstractButton$ForwardActionEvents.actionPerformed(AbstractButton.java:1817)

at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:419)

at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:257)

at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:245)

at java.awt.Component.processMouseEvent(Component.java:5093)

at java.awt.Component.processEvent(Component.java:4890)

at java.awt.Container.processEvent(Container.java:1566)

at java.awt.Component.dispatchEventImpl(Component.java:3598)

at java.awt.Container.dispatchEventImpl(Container.java:1623)

at java.awt.Component.dispatchEvent(Component.java:3439)

at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:3450)

at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3165)

at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3095)

at java.awt.Container.dispatchEventImpl(Container.java:1609)

at java.awt.Window.dispatchEventImpl(Window.java:1585)

at java.awt.Component.dispatchEvent(Component.java:3439)

at java.awt.EventQueue.dispatchEvent(EventQueue.java:450)

at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:197)

at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)

at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:144)

at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:136)

at java.awt.EventDispatchThread.run(EventDispatchThread.java:99)

queryDataSet1.close();
queryDataSet1.setQuery(new com.borland.dx.sql.dataset.QueryDescriptor(database1, sqlstatement, null, true, Load.ALL));
queryDataSet1.open();//你忘了打开DataSet

不需要啊！只要关闭就可以了！Cbuilder也是可以不需要的！你只要使用 
SQL->SetText(_T(SQL))就行了！