（急）好奇怪的问题：cannot perform this operation on a closed dataset？(200分)

请指教，谢谢！<br>代码如下，adoqBCDef和adoqBaseCode两个ADOQuery共用一个ADOConnection。<br>把红色部分注释掉能正常运行。<br>请注意，不管把adoqBCDef改成什么名字，错误信息中指出的对象实例都是“adoqBaseCode”<br>[black]procedure TForm1.FormCreate(Sender: TObject);<br>var<br>&nbsp; strSQL: string;<br>begin<br>&nbsp; strSQL := 'SELECT * FROM BCDefTable';[/black]<br><br>[red] &nbsp;with adoqBCDef do<br>&nbsp; begin<br>&nbsp; &nbsp; Close;<br>&nbsp; &nbsp; SQL.Clear;<br>&nbsp; &nbsp; SQL.Append(strSQL);<br>&nbsp; &nbsp; Open; &nbsp; &nbsp; //运行到此句出错<br>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; //错误信息是：<br>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; // &nbsp;adoqBaseCode:cannot perform this operation on a closed dataset<br>&nbsp; &nbsp; ExecSQL;<br>&nbsp; end;[/red]<br>[black]<br>&nbsp; strSQL := 'SELECT * FROM BaseCodeTable';<br>&nbsp; with adoqBaseCode do<br>&nbsp; begin<br>&nbsp; &nbsp; Close;<br>&nbsp; &nbsp; SQL.Clear;<br>&nbsp; &nbsp; SQL.Append(strSQL);<br>&nbsp; &nbsp; Open;<br>&nbsp; &nbsp; ExecSQL;<br>&nbsp; end;<br>end;[/black]

晕死，怎么又open 又 ExecSQL 的？<br>去掉 ExecSQL吧

谢谢gxw，可去掉OPEN还是一样，关键是对adoqBCDef操作，但adoqBaseCode出错

刚才又试了试，把红色部分从FormCreate事件移到FormShow就正常了。而在FormCreate中对adoqBaseCode的类似操作就没问题

应该去掉execsql而不是去掉open,因为语句是select...,需要返回数据集的。

另外ADOConnection.connected:=true最好放在所有语句之前。

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刚才又试了试，把红色部分从FormCreate事件移到FormShow就正常了。而在FormCreate中对adoqBaseCode的类似操作就没问题

呵呵，gxw真是热心。<br>ADOConnection.connected:=true是在控件里直接设的，应该在初始化的时候就执行了。<br>最开始我是用的OPEN，出错后改为EXECSQL，还是出错，干脆两个都用了。因为OPEN已经试过，所以就删除它了。<br>问题通过把那段代码移到FromShow事件里，并在FROM1第一次SHOW的时候设置一个标志，已经变通解决了，但错误原因还是没找出来。<br>为什么对adoqBCDef进行正常操作，会报adoqBaseCode出错呢？

呵呵，gxw真是热心。<br>ADOConnection.connected:=true是在控件里直接设的，应该在初始化的时候就执行了。<br>最开始我是用的OPEN，出错后改为EXECSQL，还是出错，干脆两个都用了。因为OPEN已经试过，所以就删除它了。<br>问题通过把那段代码移到FromShow事件里，并在FROM1第一次SHOW的时候设置一个标志，已经变通解决了，但错误原因还是没找出来。<br>为什么对adoqBCDef进行正常操作，会报adoqBaseCode出错呢？

应该在FORM创建时判断一下连接状态，这样确确CONNECTED都为TRUE；

原因是：你没加try...Except语句，所以第一次发生异常没及时退出FormCreate函数，接着往下执行到了第二个select语句，所以出这个错，这么改看看：<br><br>[black]procedure TForm1.FormCreate(Sender: TObject);<br>var<br>&nbsp; strSQL: string;<br>begin<br>&nbsp; strSQL := 'SELECT * FROM BCDefTable';[/black]<br><br>[red] &nbsp;with adoqBCDef do<br>&nbsp; begin<br>&nbsp; &nbsp; Close;<br>&nbsp; &nbsp; SQL.Clear;<br>&nbsp; &nbsp; SQL.Append(strSQL);<br>&nbsp; &nbsp; try<br>&nbsp; &nbsp; &nbsp; Open; &nbsp; &nbsp; //运行到此句出错<br>&nbsp; &nbsp; except<br>&nbsp; &nbsp; &nbsp; MessageDlg('adoqBCDef出误！',mtError, [mbOK], 0);<br>&nbsp; &nbsp; &nbsp; exit;<br>&nbsp; &nbsp; end;<br>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; //错误信息是：<br>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; // &nbsp;adoqBaseCode:cannot perform this operation on a closed dataset<br>&nbsp; &nbsp; //ExecSQL; 需要返回结果集（Select语句）就不要用ExecSQL，要用Open<br>&nbsp; end;[/red]<br>[black]<br>&nbsp; strSQL := 'SELECT * FROM BaseCodeTable';<br>&nbsp; with adoqBaseCode do<br>&nbsp; begin<br>&nbsp; &nbsp; Close;<br>&nbsp; &nbsp; SQL.Clear;<br>&nbsp; &nbsp; SQL.Append(strSQL);<br>&nbsp; &nbsp; try<br>&nbsp; &nbsp; &nbsp; Open;<br>&nbsp; &nbsp; except<br>&nbsp; &nbsp; &nbsp; MessageDlg('adoqBaseCode出误！',mtError, [mbOK], 0);<br>&nbsp; &nbsp; &nbsp; exit;<br>&nbsp; &nbsp; end;<br>&nbsp; &nbsp; //ExecSQL; 需要返回结果集（Select语句）就不要用ExecSQL，要用Open<br>&nbsp; end;<br>end;[/black]

多人接受答案了。