Exception handling, need help

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Hi, I have method 1 and Method 2 without try catch and Method 3 with try catch. consider following code.

Method1()
{
Method2()
' doing some stuff
}

Method2()
{
method3()
' doing some stuff
}
Method3()
{
try
catch ex as Exception
throw ex
end try 
}

if Exception occurred in Method 3 on throwing ex, code after from where method 3 is called in method2 ll not get executed also ll not get executed from method1.

Now what I need is to handle exception in Method2. consider following.

Method1( )
{
Method2( )
' doing some stuff
}

Method2( )
{
try
method3( )
' doing some stuff
catch ex as Exception
messagebox.show("")
end try
}
Method3( )
{
try
catch ex as Exception
throw ex
end try 
}

Now in this case exception from method3 ll be handle in method2 but after handling that exception I Want to stop executing code in method1 from where method 2 is called. i dont want to change anything in Method 1, because its been called from thousand of other places. :)
i can I achieve this. Please help

Posted 5-Apr-13 0:36am

Waqas Ahmad Abbasi

Updated 5-Apr-13 0:43am

Tadit Dash (ତଡିତ୍ କୁମାର ଦାଶ)

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Pheonyx · Answer 1 · 2013-04-05T00:41:00

Solution 1

Put a try catch in method 1 and re-throw the error from method 2. would be the simplest way to do it.

Posted 5-Apr-13 0:41am

Pheonyx

Comments

Waqas Ahmad Abbasi 5-Apr-13 6:53am

I cant Change Method1 as I mentioned before, I have to do something in catch of Method2 so that All code execution stops from after where Method 2 is called.

Pheonyx 5-Apr-13 6:56am

I think you need to re-evaluate your program then.

Waqas Ahmad Abbasi 5-Apr-13 7:09am

reason why i cant change in method 1 because its been called from 4000 places and i cant change in all those forms

Pheonyx 5-Apr-13 7:12am

why are you looking at changing it in all those places?
Method 1 should be defined in one location, and can be called in lots of locations.
Changing the code within method 1, should not result in 4000 changes.

If you update the method 1 code, so that it has a try/catch around where it calls method 2, then if an error occurs you can put "return;" in the catch part of it if you wish to do nothing with the exception and just exit method 1.

Waqas Ahmad Abbasi 5-Apr-13 7:34am

method 2 is common in all those,
whats happening here is method 2 returns dataset, and in method 1 they are doing some thing like this
if ds.table(0).rows.count > 0 {}

what was happening before that when method 3 throws exception than no effect happen here as this ll not get executed in method 1, now method 2 returns nothing and all these method 1 produces new exceptions as there are no checks like this
if ds isnot nothing andalso ds.Tables.count > 0 etc etc. :(

Pheonyx 5-Apr-13 7:53am

If all your method 1's are checking that the dataset returned from method 2 has rows, then why not just return a dataset containing a table with no rows? then it shouldn't process the result.
If that doesn't work, then you are out of luck I think.

Waqas Ahmad Abbasi 5-Apr-13 8:54am

I am out of luck :(

Matthew Faithfull · Answer 2 · 2013-04-05T00:47:00

Solution 2

If I understand you correctly then what you need is to rethrow the exception in Method2 just as you do in Method3 within the catch clause.

messagebox.show("");
throw ex;

If you do this then the remaining code in Method1 will not get executed, it wil get bypassed in the search for an exception handler.
If you don't want your code to crash wih an unhandled exception fault you'll need to have an exception handler further down the stack in something that ultimately calls Method1 so that the exception will get caught somewhere.

Generally though this is not looking like an ideal solution. Complex flow of control like this has a major tendency to lead to memory leaks, especially when excepton handling is involved. If these 'exceptional' cases are in fact part of the design of how the system is intended to work then they aren't really exceptional and should be coded for in another way.

Posted 5-Apr-13 0:47am

Matthew Faithfull

Comments

Waqas Ahmad Abbasi 5-Apr-13 6:52am

This is what I tried But it ll kill purpose, because am showing custom error in Method2, after showing error if I throw ex again, then default system exception ll also get shown, i dont want to show default Exception by throwing ex again :(

Matthew Faithfull 5-Apr-13 7:10am

The only way to avoid the default exception is, as I mentioned to put a catch in a function higher up (That's all the default exception is anyway). Perhaps install you own default exception handler in main that silently catches this rethrown exception from Method2 and doesn't rethrow it again. This is not recommended practice but it will solve your immediate problem.

Waqas Ahmad Abbasi 5-Apr-13 7:36am

thats the point, my main is actually method 1, which is actually hundreds of forms load events, that is calling method 2,
method 2 is common in all those, whats happening here is method 2 returns dataset, and in method 1 they are doing some thing like this if ds.table(0).rows.count > 0 {} what was happening before that when method 3 throws exception than no effect happen here as this ll not get executed in method 1, now method 2 returns nothing and all these method 1 produces new exceptions as there are no checks like this if ds isnot nothing andalso ds.Tables.count > 0 etc etc. :(

Matthew Faithfull 5-Apr-13 7:40am

Then it looks like you are out of luck, you'll have to appeal to whoever owns Method1 to be able to change the design.