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how can i get back to tryp block after an exception was thrown?

Posted on 2009-05-06
10
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Last Modified: 2013-12-17
hello experts,

i loop trought a DateTime[],
while looping i get current element,
i need the precedent elemnet too!
the prob is that for the first element there's no precendent.

i dont want to test if it's first to avoid the IndexOutOfException to raise,

my question:
what can i do, if there's a possibility, in order to continue the process after the Exception was
throws, is there a way to get back  to the try block with incrementing, the index, here 's my i variable?

i add the code,

all infos are welcome.
thanks in advance.
private ArrayList GetDrainsObj(DateTime[] aDrainDateList)
        {
            Drain _tempDrain = null;
            ArrayList _allDrains = new ArrayList();
            int index = 0;
 
            try
            {
                for (int i = 1; i < aDrainDateList.Length; i++ )
                {
                    DateTime current_drain = aDrainDateList[index];
                    DateTime  last_drain = aDrainDateList[index-1];
                    _tempDrain = new Drain(id_, Ecolog_.Id_int, current_drain, last_drain, DateTime.Now);
                    _allDrains.Add(_tempDrain);
                }
            }catch(IndexOutOfRangeException)
            {
                
            }
 
            return _allDrains;
        }

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Question by:toshi_
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10 Comments
 
LVL 8

Assisted Solution

by:OBonio
OBonio earned 100 total points
ID: 24313692
I would aim not to throw the exception!  Checking whether you are on the first element or not is far better than letting an exception be thrown!

That said, try this :



private ArrayList GetDrainsObj(DateTime[] aDrainDateList)
        {
            Drain _tempDrain = null;
            ArrayList _allDrains = new ArrayList();
            int index = 0;
 
            for (int i = 1; i < aDrainDateList.Length; i++ )
            {
                DateTime current_drain = aDrainDateList[index];
                DateTime  last_drain;
                try
                {
                  last_drain = = aDrainDateList[index-1]; 
                } 
                catch(IndexOutOfRangeException)
                {
                  last_drain = null;
                }
 
                if(last_drain!=null)
                {
                  _tempDrain = new Drain(id_, Ecolog_.Id_int, current_drain, last_drain, DateTime.Now);
                  _allDrains.Add(_tempDrain);
                }
            }
 
            return _allDrains;
        }

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LVL 16

Assisted Solution

by:CuteBug
CuteBug earned 100 total points
ID: 24313702
Place the try catch block within your for loop and in the catch section you can add continue;
private ArrayList GetDrainsObj(DateTime[] aDrainDateList)
        {
            Drain _tempDrain = null;
            ArrayList _allDrains = new ArrayList();
            int index = 0;
 
            for (int i = 1; i < aDrainDateList.Length; i++ )
            {
                  try
                  {
                    DateTime current_drain = aDrainDateList[index];
                    DateTime  last_drain = aDrainDateList[index-1];
                    _tempDrain = new Drain(id_, Ecolog_.Id_int, current_drain, last_drain, DateTime.Now);
                    _allDrains.Add(_tempDrain);
                  }
                  catch(IndexOutOfRangeException){
                    continue;
                  }                
            }
 
            return _allDrains;
        }

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LVL 9

Assisted Solution

by:tillgeffken
tillgeffken earned 100 total points
ID: 24313713
From my point of view its bad practice to aim for exceptions, that's why they're called exceptions. What's the purpose of this? Your Drain class requires a last_drain so why not skip it alltogther?

private ArrayList GetDrainsObj(DateTime[] aDrainDateList)
        {
            Drain _tempDrain = null;
            ArrayList _allDrains = new ArrayList();
            int index = 1;
 
            try
            {
                for (int i = 2; i < aDrainDateList.Length; i++ )
                {
                    DateTime current_drain = aDrainDateList[index];
                    DateTime  last_drain = aDrainDateList[index-1];
                    _tempDrain = new Drain(id_, Ecolog_.Id_int, current_drain, last_drain, DateTime.Now);
                    _allDrains.Add(_tempDrain);
                }
            }catch(IndexOutOfRangeException)
            {
                
            }
 
            return _allDrains;
        }

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LVL 16

Expert Comment

by:CuteBug
ID: 24313722
Obonio's has provided a better solution.
0
 
LVL 9

Expert Comment

by:tillgeffken
ID: 24313763
I don't see the point in even processing index 0 when you already know that it can only fail.
0
 
LVL 16

Expert Comment

by:CuteBug
ID: 24313764
Another method is to loop backward. This will solve it altogether.

After the loop ends, just reverse the resultant array.
private ArrayList GetDrainsObj(DateTime[] aDrainDateList)
        {
            Drain _tempDrain = null;
            ArrayList _allDrains = new ArrayList();
            int index = 0;
 
            try
            {
                for (int i = aDrainDateList.Length - 1; i > 0; i-- )
                {
                    DateTime current_drain = aDrainDateList[index];
                    DateTime  last_drain = aDrainDateList[index-1];
                    _tempDrain = new Drain(id_, Ecolog_.Id_int, current_drain, last_drain, DateTime.Now);
                    _allDrains.Add(_tempDrain);
                }
            }catch(IndexOutOfRangeException)
            {
                
            }
 
            // Reverse the order
            Array.Reverse(_allDrains);
 
            return _allDrains;
        }

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LVL 4

Accepted Solution

by:
cauos earned 200 total points
ID: 24313813
yes Obonio's has provided a better solution.but the error occured in the index not index - 1 (he started the for loop from 1 )
 for (int i = 1; i < aDrainDateList.Length; i++ )
            {
                DateTime current_drain;
                DateTime  last_drain =aDrainDateList[index-1];                
                try
                {
                   current_drain = aDrainDateList[index];
                } 
                catch(IndexOutOfRangeException)
                {
                 current_drain= null;
                }
 
                if(current_drain!=null)
                {
                  _tempDrain = new Drain(id_, Ecolog_.Id_int, current_drain, last_drain, DateTime.Now);
                  _allDrains.Add(_tempDrain);
                }
            }

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0
 
LVL 9

Expert Comment

by:tillgeffken
ID: 24313847
I still think there is no problem in the first place. You're creating one by trying to parse data of which you know that it doesn't exist. Or am i missing something?
0
 
LVL 4

Expert Comment

by:cauos
ID: 24313937
you right tillgeffken, there is no logic by doing this if he want to return the array list before end the method he can add the finally statement and return the array list.
private ArrayList GetDrainsObj(DateTime[] aDrainDateList)
        {
            Drain _tempDrain = null;
            ArrayList _allDrains = new ArrayList();
            int index = 1;
 
            try
            {
                for (int i = 2; i < aDrainDateList.Length; i++ )
                {
                    DateTime current_drain = aDrainDateList[index];
                    DateTime  last_drain = aDrainDateList[index-1];
                    _tempDrain = new Drain(id_, Ecolog_.Id_int, current_drain, last_drain, DateTime.Now);
                    _allDrains.Add(_tempDrain);
                }
            }catch(IndexOutOfRangeException)
            {
                
            }
        finally
         {
            return _allDrains;
         }
        }

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LVL 9

Expert Comment

by:tillgeffken
ID: 24314014
Actually i left the Exception in there because i was too lazy to delete it. The following should be just fine (at least you won't get an IndexOutOfRangeException)

private ArrayList GetDrainsObj(DateTime[] aDrainDateList)
{
 Drain _tempDrain = null;
 ArrayList _allDrains = new ArrayList();
 int index = 1;
 
 for (int i = 2; i < aDrainDateList.Length; i++ )
 {
  DateTime current_drain = aDrainDateList[index];
  DateTime  last_drain = aDrainDateList[index-1];
  _tempDrain = new Drain(id_, Ecolog_.Id_int, current_drain, last_drain, DateTime.Now);
  _allDrains.Add(_tempDrain);
 }
 return _allDrains;
}

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