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

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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toshi_
Asked:
toshi_
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4 Solutions
 
OBonioCommented:
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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CuteBugCommented:
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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tillgeffkenCommented:
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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CuteBugCommented:
Obonio's has provided a better solution.
0
 
tillgeffkenCommented:
I don't see the point in even processing index 0 when you already know that it can only fail.
0
 
CuteBugCommented:
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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cauosCommented:
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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tillgeffkenCommented:
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
 
cauosCommented:
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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tillgeffkenCommented:
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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