An interesting problem I keep coming across is how to re-order an arraylist item up or down, it's something I've needed to use on a number of applications, so I figured it's about time I got my head round the problem, and it's surprisingly simple.

First we create an Arraylist and populate it:        

    ArrayList MyRA = new ArrayList();               
    MyRA.Add("Item1");        
    MyRA.Add("Item2");        
    MyRA.Add("Item3");        
    MyRA.Add("Item4");        
    MyRA.Add("Item5");

Next we identify the item we want to move:        

    String myItem = "Item4";

And create an integer to hold the position of the item:        

    Int32 myIndex = new Int32();

Now get the position:        

    myIndex = MyRA.IndexOf(myItem);

Almost there, now we insert the Item at that the position before it's current on (Position - 1):        

    MyRA.Insert((myIndex - 1), myItem);

Finally we need to remove the old item, it's position would have moved up one since we've added an extra item:                

    MyRA.RemoveAt((myIndex + 1)); 

So if you're in a hurry and just want the full code here you go:        

        ArrayList MyRA = new ArrayList();
        String myItem = "Item4";
        Int32 myIndex = new Int32();

        MyRA.Add("Item1");
        MyRA.Add("Item2");
        MyRA.Add("Item3");
        MyRA.Add("Item4");
        MyRA.Add("Item5");

        myIndex = MyRA.IndexOf(myItem);
        MyRA.Insert((myIndex - 1), myItem);
        MyRA.RemoveAt((myIndex + 1));

Of course this only moves items down the list, to move them up simply reverse the numbers on the last two lines:        

    MyRA.Insert((myIndex + 1), myItem);        
    MyRA.RemoveAt((myIndex - 1));

Happy Coding :0)

Tags: ArrayList, Re-order, c#