C# sorting elements on a listbox

Question

4.00/5 (1 vote)

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I have a 20 elements array and I want to add them to a listbox is a specific order. I have a counter for adding elements on the array so I want the list box to show the last element added on top and then the one before it.
For Example if my last element was added when the counter was 4 I want the element to be shown on the list box in this order

{4,3,2,1,0,19,18,17,16,15,14,13,12,11,10,9,8,7,6,5}

What I have tried:

C#

string [] ListaServizi1 = new string[] { item, item2, item3, item4, item5, item6, item7, item8, item9, item10, item11, item12, item13, item14, item15, item16, item17, item18, item19, item20 };
                            if (historylistBox1.Items.Count == 20) 
                            {
                                historylistBox1.Items.Clear();
                            }
                            int startfrom =  tcounter;
                            
                          int  startover = 0;
                         int   index = 0;
                            for (int i=0; i <= 20; i++)
                            {
                                if (startfrom<listaservizi1.length mode="hold" />                                {
                                    index++;
                                    historylistBox1.Items.Add(index + "."+ListaServizi1[startfrom]);
                                    startfrom++;
                                   
                                 }
                                
                                else if(startfrom >= ListaServizi1.Length)
                                {
                                    index++;
                                    historylistBox1.Items.Add(index + "." + ListaServizi1[startover]);
                                    startover++;
                                    startfrom++;
                                  

                                }

Posted 21-Feb-16 21:22pm

coding star

Updated 21-Feb-16 23:55pm

Maciej Los

v2

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3 solutions

Solution 3

This is not really a sort problem, you want the items in reverse order and with a rotation.

First of all the pitfall:

C#

for (int i=0; i <= 20; i++)

is wrong because it loop 21 times. Use i<20

ListaServizi1[i] read items in order.
ListaServizi1[19-i] read items in reverse order.
ListaServizi1[(5+19-i)%20] read items in reverse order with rotation.

Your code simplified should look like:

C#

for (int i=0; i < 20; i++)
{
        historylistBox1.Items.Add((i+1) + "."+ListaServizi1[(5+19-i)%20]);

    }

Posted 21-Feb-16 23:55pm

Patrice T

Updated 21-Feb-16 23:59pm

v3

Comments

Maciej Los 22-Feb-16 6:05am

It looks pretty good, but does not resolve an "order" issue. Why? An algorithm to sort data is OK, but it produces string-based-output, like: {"0.A", "1.A", ..., "20.A"}, etc. So...

Patrice T 22-Feb-16 6:13am

My code should exactly what the original code does.
What is the problem ?
By the way it is {"1.A", ..., "20.A"}

Maciej Los 22-Feb-16 6:45am

I wanted to say that order of elements in the ListBox will be wrong: {"1.A", "11.A", "12.A", ..., "2.A", "20.A"}. Got it?

Patrice T 22-Feb-16 7:01am

Do you mean that historylistBox1.Items.Add is sorting the items ?

Maciej Los 22-Feb-16 7:09am

OMG, i'm an idiot! You're right! ListBox adds new item on the end of list!
5ed!

Patrice T 22-Feb-16 7:11am

Thank you

Solution 1

This is asked before but lucky this is not stackoverflow

C# - Sorting items in a listbox...![^]

Posted 21-Feb-16 21:30pm

Beginner Luck

Comments

coding star 22-Feb-16 3:37am

The questions' titles are the same ,but the sorting ways are totally different.

Beginner Luck 22-Feb-16 3:38am

because it is using linq method.

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BillWoodruff · Accepted Answer · 2016-02-21T23:21:00

On February 3, I posted a solution here for a "generic stack" that you could easily adapt ... without modification ... to your task: [^].

Using the code in that example, your stack might be declared like this:

// in Form Scope

// define your Array of Strings ...

private const int StringStackDepth = 20;

private StackT<string> stringStack = new StackT<string>(StringStackDepth);

private BindingSource bindSource = new BindingSource();

// in a Method or EventHanlder
private void Form1_Load(object sender, EventArgs e)
{
    foreach (string s in ListaServizi1)
    {
        StringStack.Push(s);    
    }
    
    bindSource = new BindingSource();
    bindSource.DataSource = StringStack;
    listBox1.DataSource = bindSource;
}

Now the "hard part" here is getting the ListBox to update when you have modified the Stack. Here's an example of what you have to do:

C#

StringStack.Push("item 21");
bindSource = new BindingSource();
bindSource.DataSource = StringStack;
listBox1.DataSource = bindSource;

I suggest you consider the possible "cost" (computation ? memory use ?) making many frequent updates of the Stack ... note that I have never tried to really evaluate this technically.

If I were using this generic Stack in this way, I'd probably modify its code to raise an Event when the data changed; then the user would subscribe to that event, and perform the UI update in that EventHandler. This would be easy to do.

Of course, I might also be associating stack values with some other object/entity in a Dictionary, or other data structure, and then setting the 'ValueMember of the ListBox.
If you are using a ListView, binding is much more difficult, but you can find resources on how to do it, like here, on CodeProject: [^], or here: [^].

I assume this is a Windows Forms Project, and you are using a ListBox, or ListView Control: if that's not correct please revise your post.

Have you studied how to do binding, and use 'DataSource, 'ValueMember, and 'DisplayMember tools ?