Problem with adding items to lists

[soryjero]

hello, i am coding a program but i have a problem with it.

 

i have defined a list of items and a item of the same class of the list to read a item and add it to list. i read it and i add it to list. first time is everything ok but if i read it more times, first item i add is the same as second. i mean if for example first item is value 1 and second is value 3, when i read first time item value of list is 1 but second time, both elements of the list are 3.

i dont know why this can be happen.

 

Could anyone help me please?

[Wizatek]

U are trying to add the same class and just changed some values.

 

The values inside a class are passed by reference.

 

So lets say your class named Items. And u do this.

 

Items itemA = new Items();

itemA.id = 1;

 

Items itemB = itemA;

itemB.id = 2;

 

U would think that itemB is a copy of itemA with only a different id.

But its not. itemB is a reference to itemA. So everything u change in itemB gets changed in itemA aswell.

 

If u really want to make a copy lookup MemberwiseClone()

[soryjero]

U are trying to add the same class and just changed some values.

 

The values inside a class are passed by reference.

 

So lets say your class named Items. And u do this.

 

Items itemA = new Items();

itemA.id = 1;

 

Items itemB = itemA;

itemB.id = 2;

 

U would think that itemB is a copy of itemA with only a different id.

But its not. itemB is a reference to itemA. So everything u change in itemB gets changed in itemA aswell.

 

If u really want to make a copy lookup MemberwiseClone()

i think i havent explain my problem well.

 

i have this:

 

List<Items> itemA = new List<Items>();

Items itemB;

 

and i want to add elements to list so i do this:

 

for(int i = 0; i < 5; i++)

{

itemB.ID = br.readInt32();

itemB.power = br.readInt32();

ItemA.Add(itemB);

}

 

and the result should be these:

 

itemA[0].ID = 1

ItemA[0].power = 1

 

itemA[1].ID = 2

ItemA[1].power = 2

 

itemA[2].ID = 3

ItemA[2].power = 3

 

itemA[3].ID = 4

ItemA[3].power = 4

 

itemA[4].ID = 5

ItemA[4].power = 5

 

but instead of this, the results are these:

 

itemA[0].ID = 5

ItemA[0].power = 5

 

itemA[1].ID = 5

ItemA[1].power = 5

 

itemA[2].ID = 5

ItemA[2].power = 5

 

itemA[3].ID = 5

ItemA[3].power = 5

 

itemA[4].ID = 5

ItemA[4].power = 5

 

and i dunno why this happen

[Wizatek]

Try this

 

for(int i = 0; i

{

itemB = new Items();

itemB.ID = br.readInt32();

itemB.power = br.readInt32();

ItemA.Add(itemB);

}

 

 

The reason why it was happening is because of the reference. 

itemB stays the same when u dont initialize it again. 

And even if added to the list, itemB is still itemB.

So basically u just added 5x the same object to the list that all point to the same data.

[soryjero]

Try this

 

for(int i = 0; i < 5; i++)

{

itemB = new Items();

itemB.ID = br.readInt32();

itemB.power = br.readInt32();

ItemA.Add(itemB);

}

 

 

The reason why it was happening is because of the reference. 

itemB stays the same when u dont initialize it again. 

And even if added to the list, itemB is still itemB.

So basically u just added 5x the same object to the list that all point to the same data.

 

yeah, it works. thans so much again @2