blocks|key|3825722|text|这是一个在调用方法之前可以检查到的错误条件吗？如果是这样，抛出一个异常。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3825723|否则，return一些有意义的东西(例如，如果它是一个void函数，则将其更改为返回一个bool，然后返回false)。|offset|length|style|CODE|3825724|entityMap^0|0|3|6|R|4|18|4|1H|5|0^^$0|@$1|2|3|4|5|6|7|J|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|K|8|@$D|L|E|M|F|G]|$D|N|E|O|F|G]|$D|P|E|Q|F|G]|$D|R|E|S|F|G]]|9|@]|A|$]]|$1|H|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|I|$]]

Is it an error condition that could have been checked before calling the method? If so, throw an exception.

Otherwise, <code>return</code> something meaningful (e.g. if it's a <code>void</code> function, change it to return a <code>bool</code>, and return <code>false</code>).

blocks|key|1169259|text|这就是异常的用处。抛出异常以终止函数和任何调用方，直到到达异常处理程序为止。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1169260|请注意，只有在发生异常时才应该这样做；异常不应该用作“不同类型的”返回值，因为就代码大小(无论是否抛出)和运行时间(如果抛出)而言，异常比正常返回的代价更高。|1169261|就返回到您之前的状态而言，如果您的代码和任何通过其进行调用的库代码都是以异常安全的方式编写的，那么这是可能的。|1169262|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|H|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|I|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|J|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|G|$]]

This is what exceptions are for. You throw an exception to terminate the function and any caller, until an exception handler is reached. 

Note that this should only be done if something exceptional has occurred; exceptions shouldn't be used as a "different kind of" return value, as they are more costly in terms of code size (whether thrown or not) and running time (if thrown) , than normals returns. 

As far as returning to the state you had before, this is possible if your code and any library code through which the call proceeded was written in an exception safe manner.

blocks|key|1162338|text|您可以使用Memento+pattern实现对象回档。来自here的。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1162339|1162340|管理员将对创建者执行某些操作，但希望能够撤消更改。管理员首先向发起人索要纪念品。然后，它执行它要执行的任何操作(或操作序列)。为了回滚到操作之前的状态，它将memento对象返回给发起者。|blockquote|1162341|1162342|1162343|收到指示应回滚的事件后，可以撤消更改并返回到调用方。这里有一些关于为什么不应该使用Thread.Abort的info.+and+links。|1162344|entityMap|0|LINK|mutability|MUTABLE|url|http://www.dofactory.com/Patterns/PatternMemento.aspx|1|http://en.wikipedia.org/wiki/Memento_pattern|2|http://msmvps.com/blogs/peterritchie/archive/2007/08/22/thead-abort-is-a-sign-of-a-poorly-designed-program.aspx^0|5|F|0|T|4|1|0|0|0|0|0|1I|F|2|0^^$0|@$1|2|3|4|5|6|7|X|8|@]|9|@$A|Y|B|Z|1|10]|$A|11|B|12|1|13]]|C|$]]|$1|D|3|-4|5|6|7|14|8|@]|9|@]|C|$]]|$1|E|3|F|5|G|7|15|8|@]|9|@]|C|$]]|$1|H|3|-4|5|6|7|16|8|@]|9|@]|C|$]]|$1|I|3|-4|5|6|7|17|8|@]|9|@]|C|$]]|$1|J|3|K|5|6|7|18|8|@]|9|@$A|19|B|1A|1|1B]]|C|$]]|$1|L|3|-4|5|6|7|1C|8|@]|9|@]|C|$]]]|M|$N|$5|O|P|Q|C|$R|S]]|T|$5|O|P|Q|C|$R|U]]|V|$5|O|P|Q|C|$R|W]]]]

You can use the <a href="http://www.dofactory.com/Patterns/PatternMemento.aspx" rel="nofollow noreferrer">Memento pattern</a> to implement object rollback. From <a href="http://en.wikipedia.org/wiki/Memento_pattern" rel="nofollow noreferrer">here</a> ...

<blockquote>
 The caretaker is going to do something
 to the originator, but wants to be
 able to undo the change. The caretaker
 first asks the originator for a
 memento object. Then it does whatever
 operation (or sequence of operations)
 it was going to do. To roll back to
 the state before the operations, it
 returns the memento object to the
 originator.
</blockquote>

Once you receive the event that indicates that you should roll back, you can undo the change and return to the caller. Here is some <a href="http://msmvps.com/blogs/peterritchie/archive/2007/08/22/thead-abort-is-a-sign-of-a-poorly-designed-program.aspx" rel="nofollow noreferrer">info. and links</a> on why you should not use Thread.Abort.

blocks|key|1169311|text|我猜你说的是对象事务或事务内存。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1169312|您至少可以记录正在修改的对象的状态(赋值)，并在赋值条件失败时将旧值写入其中。|1169313|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

I guess you are talking on the lines of object transactions OR transactional memory. 

The least you can do is you can record the state (assignments) of the object being modified and write the old values on it when the condition to assignment fails.

blocks|key|3826514|text|如果我没理解错的话，你希望在某些条件为真的情况下撤销对某些变量所做的更改？如果是这种情况，您将需要存储所有变量(或作为一个整体的类)的副本。然后，如果您的条件为真，那么在从函数返回之前，您必须将所有这些变量恢复到它们的初始状态。它应该是这样的：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3826515|//+In+order+to+clone+your+variable,+you+may+need+to+inherit+from+
//+ICloneable+and+implement+the+Clone+function.
bool+MyFunction(ICloneable+c)
{
++++//+1.+Create+a+copy+of+your+variable
++++ICloneable+clone+=+c.Clone();

++++//+2.+Do+whatever+you+want+in+here
++++...

++++//+3.+Now+check+your+condition
++++if+(condition)
++++{
++++++++//+Copy+all+the+attributes+back+across+to+c+from+your+clone
++++++++//+(You'll+have+to+write+the+ResetAttributes+method+yourself)
++++++++c.ResetAttributes(clone);

++++++++//+Put+a+message+box+up
++++++++MessageBox.Show("This+failed!");

++++++++//+Now+let+the+caller+know+that+the+function+failed
++++++++return+false;
++++}
++++else
++++{
++++++++//+Let+the+caller+know+that+the+function+succeeded
++++++++return+true;
++++}
}|code-block|syntax|javascript|3826516|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

If I'm understanding you correctly, you wish to undo changes you have made to certain variables if some condition is true? If that's the case, you will want to store a copy of all your variables (or your class as a whole). Then, if your condition comes up true, you'll have to revert all those variables to their initial state before returning from your function. It would be something like this:

<pre><code>// In order to clone your variable, you may need to inherit from 
// ICloneable and implement the Clone function.
bool MyFunction(ICloneable c)
{
 // 1. Create a copy of your variable
 ICloneable clone = c.Clone();

 // 2. Do whatever you want in here
 ...

 // 3. Now check your condition
 if (condition)
 {
 // Copy all the attributes back across to c from your clone
 // (You'll have to write the ResetAttributes method yourself)
 c.ResetAttributes(clone);

 // Put a message box up
 MessageBox.Show("This failed!");

 // Now let the caller know that the function failed
 return false;
 }
 else
 {
 // Let the caller know that the function succeeded
 return true;
 }
}
</code></pre>

blocks|key|605105|text|另一种解决方案，与上面的方案略有不同：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|605106|在你的示例方法中不时地检查一下指定的条件。|605107|public+void+MyMethod()
{
some+code

if+(conditionOccurred+==+true){+reset+to+the+previous+state+and+exit;}

more+code
}|code-block|syntax|javascript|605108|这可能不是本书所说的，但如果你不经常使用它，它给出了非常简单和可读的代码。|605109|如果您想要返回到程序状态，我可能不必提及您需要保存程序的状态，并且您需要编写一些代码来使您返回到这种状态。|605110|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|Q|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

Another solution, differing slightly from those above:

Check for the specified condition a bit now and then in your sample method.

<pre><code>public void MyMethod()
{
some code

if (conditionOccurred == true){ reset to the previous state and exit;}

more code
}
</code></pre>

This is probably not according to the book, but it gives quite simple and readable code if you don't use it too often.

I probably don't have to mention that you need save the program's state if you want to be able to return to it, and you need to write some code that returns you to this state.

blocks|key|4669432|text|堆上的通用回滚功能对我来说是闻所未闻的。但是您可以使用命令模式来获取撤消功能，并将其用于回滚：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4669433|http://en.wikipedia.org/wiki/Command_pattern|offset|length|4669434|从本质上讲，您将操作封装在一个对象中，该对象存储了足够的更改信息，从而可以撤消更改。您将该对象推送到堆栈上，当您的条件发生时，您可以从堆栈中弹出所有命令对象并撤消它们。如果没有更多关于你的案例的信息，就很难给出更具体的信息或判断这是否适用于你。|4669435|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|18|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@$D|Q|E|R|1|S]]|A|$]]|$1|F|3|G|5|6|7|T|8|@]|9|@]|A|$]]|$1|H|3|-4|5|6|7|U|8|@]|9|@]|A|$]]]|I|$J|$5|K|L|M|A|$N|C]]]]

A generic rollback functionality on the heap is for me unheard of. But you can use the Command pattern to get undo functionality and use it for rolling back:

<a href="http://en.wikipedia.org/wiki/Command_pattern" rel="nofollow noreferrer">http://en.wikipedia.org/wiki/Command_pattern</a>

Essentially you encapsulate an operation in an object that stores enough information of the change that it can undo it. You push that object onto a stack, and when your condition occurs, you go pop all command objects from the stack and undo them. Without more information about your case it's difficult to give more specific information or tell whether this is applicable for you.

if a condition occurs i have to stop the execution of the current method call and return to the state before the method call .how can i do it .. suppose a i am executing some sample method and a condition occurs and i am prompting a message box and then i want to return to state before this function call

how to stop the execution of current method call

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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如果出现条件，我必须停止当前方法调用的执行，并返回到方法调用.how之前的状态。假设我正在执行某个示例方法，并且发生了一个条件，我正在提示一个消息框，然后我想返回到此函数调用之前的状态

问如何停止当前方法调用的执行
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问如何停止当前方法调用的执行EN