Try catch finally: 如果没有抛出异常，就做点什么

Question

I'm wondering, is there a way to only execute a block if no exception was thrown?

The best I can come up with is this:

bool exception = false;
try{
    // something
}catch(Exception e){
    exception = true;
}finally{
    if(!exception){
        // i can do what i want here
    } 
}

Is there a better way?

Answer 1

Sure there is: put it at the bottom of the try block.

try{
    // something
    // i can do what i want here
}catch(Exception e){
    // handle exception
}

This is not entirely equivalent to your original code in the sense that if "what you want" throws, the exception will be caught locally (this would not happen with your original scheme). This is something you might or might not care about, and there's a good chance that the different behavior is also the correct one.

If you want to bring the old behavior back, you can also use this variant that doesn't require a finally just for the sake of writing the "if no exceptions" condition:

var checkpointReached = false;
try{
    // something
    checkpointReached = true;
    // i can do what i want here
}catch(Exception e){
    if (checkpointReached) throw; // don't handle exceptions after the checkpoint
    // handle exception
}

Answer 2

You don't need the finally clause.

A solution :

bool exception = false;
try{
    // something
}catch(Exception e){
    exception = true;
}
if(!exception){
     // u can do what u want here
} 

Usually you'll simply have a return in your catch clause so that you don't even have to test :

try{
    // something
}catch(Exception e){
   // do things
   return;
}
// u can do what u want here

or (depending on the use case and generally less clear, especially if you have more than one exception expected - you don't want to have try-catch nesting...) :

try{
    // something
    // u can do what u want here
}catch(Exception e){
   // do things
}

Answer 3

Can you structure your code that the doSomething is the last statement in the block and it doesn't throw?

bool exception = false;
try{
  // something
  doSomething();
} catch {
}
finally {
}

Answer 4

是的：把它放在 try 块的末尾:)

Answer 5

Nope - what you've got is probably the best way to do it in C#.

This is assuming that:

• You don't want the "i can do what i want here" code to run at the bottom of your try block. (Perhaps because you don't want exceptions in that code to be handled by the main catch block.)
• You don't want the "i can do what i want here" code to run entirely outside of the try...catch...finally structure. (Perhaps because you want that code to run before some other code that's sitting inside the finally block.)

Answer 6

While there is nothing wrong with your code, it's unnecessary. Simply put the code you wish to execute at the bottom of the try block:

try {
    ...
    // No errors to this point, run what you wanted to run in the finally.
}
catch(Exception e) {
    ...
}

Answer 7

I believe you are looking for a try inside your try:

try{
    // something

    try{
        // something else not interfering with first try
    } catch(Exception innerEx){
        // something else threw this innerEx
    }

}catch(Exception outerEx){
    // something threw this outerEx
}

Although this is generally considered bad practice, I like it more than the flag version.