Move List Data to two diff lists

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I have a List<classa> , it contains n elements . I want to separate the lists into two diff lists with small changes to the Item.

EX: List<classa> obj=new List<classa>();
It has some elements

i want to move even index entry in obj to List<classa> objEven , at the same time i want to move entries whose index is divisible by 4 to List<classa> objDiv4. while moving Change one property value to EVEN and Div4.

C#

class Program
   {
       static void Main(string[] args)
       {
           List<classa> obj = new List<classa>();
           List<classa> objEven = new List<classa>();
           List<classa> objDiv4 = new List<classa>();
           int iCounter = 1;
           for (int i = 1; i <= 100; i++)
               obj.Add(new classA { ID = i, Notes = "Notes " + i.ToString() });

           classA temp = new classA();
           foreach (classA lobj in obj)
           {
               temp = lobj;
               if (iCounter % 2 == 0)
               {
                   temp.Notes = "EVEN";
                   objEven.Add(temp);
               }
               temp = lobj;
               if (iCounter % 4 == 0)
               {
                   temp.Notes = "DIV4";
                   objDiv4.Add(temp);
               }
               iCounter++;
           }

           foreach(classA lobj in objEven)
           {
               Console.Write(lobj.Notes+"  ");
           }
           Console.Read();
       }
   }

   class classA
   {
       public int ID { get; set; }

       public string Notes { get; set; }
   }

problem here objEven is containing elements with notes as DIV4.

Posted 31-Jan-15 7:33am

JagadishBB

Updated 31-Jan-15 7:51am

CPallini

v3

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Comments

Ramza360 31-Jan-15 14:20pm

The reason for this is that your setting temp to the same object, and this is creating a reference in the objEven list and objDiv4 list.

2 solutions

Solution 1

Your problem is that items with IDs which are dividable by 4 gets checked twice:
once if their ID is even and once if their ID is a multiple of 4 because the 2 if statements are unrelated.

Since every ID which is dividable by 4 is also dividable by 2 I'd place second if statement inside the first one like so:

C#

if (iCounter % 2 == 0)
{
  if (iCounter % 4 == 0) // multiples of 4 will enter this scope
  {
      temp.Notes = &quot;DIV4&quot;;
      objDiv4.Add(temp);
  }
  else // other even numbers will enter this one
  {
    temp.Notes = "EVEN";
    objEven.Add(temp);
  }
}

That way items with even ID's get into either objDiv4 or ovjEven and necessarily not into both.

Posted 31-Jan-15 8:05am

Member 11353972

Updated 31-Jan-15 8:07am

v2

Comments

JagadishBB 31-Jan-15 14:16pm

Thq for your Reply ...
Items which are divisible by 4 are also even numbers so it should exist in both objDiv4 and objEven but notes as different.

Ramza360 31-Jan-15 14:21pm

Try Solution2 :)

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Ramza360 · Accepted Answer · 2015-01-31T08:18:00

Solution 2

First off since your using a list, its easier to use the for instead of foreach.
Also my solution is assuming your don't care if the ID is even or not, just the index.

If you want to do by index, substitute the i % 2 and i % 4 with obj[i].ID.

C#

classA temp = null;
for (int i = 0; i < obj.Count - 1; i++)
{
    temp = new classA();
    if (i % 2 == 0)
    {
        temp.ID = obj[i].ID;
        temp.Notes = "EVEN";
        objEven.Add(temp);
    }

    temp = new classA();
    if (i % 4 == 0)
    {
        temp.ID = obj[i].ID;
        temp.Notes = "DIV4";
        objDiv4.Add(temp);
    }
}

Posted 31-Jan-15 8:18am

Ramza360

Updated 31-Jan-15 8:28am

v4

Comments

JagadishBB 31-Jan-15 14:34pm

Thank You So much ...It solved my Problem. But i didn't understood when an object is modified and moved to some list . After that if we change it y it is reflecting in prev moved object. Below one dont have any problem , but with objects why is different

JagadishBB 31-Jan-15 14:35pm

ArrayList obj = new ArrayList();
ArrayList objEven = new ArrayList();
ArrayList objDiv4 = new ArrayList();

for (int i = 1; i <= 100; i++)
obj.Add(i.ToString() + " ");

int iCounter = 1;
foreach (string lobj in obj)
{
string str = lobj;
if (iCounter % 2 == 0)
{
str = str + " EVEN";
objEven.Add(str);
}
if (iCounter % 4 == 0)
{
str = str + " DIV4";
objDiv4.Add(str);
}
iCounter++;
}

foreach (string lobj in objEven)
{
Console.Write(lobj + " ");
}
Console.Read();

Ramza360 31-Jan-15 14:41pm

It was basically creating a reference to the classA object rather than a copy, so changing one, changes the other.

JagadishBB 31-Jan-15 14:50pm

Thq for th answer .
Why it is not happenning the same with string object.Any memory allocation side difference is there.

Ramza360 31-Jan-15 15:08pm

That's a good question, not entirely sure how to answer it. Perhaps someone else can enlighten us both there.