C# Discussion Boards - CodeProject

Re: Adding Items in a Class

4-Jan-18 21:27

I'd like to add to the useful answer Mycroft gave you ...

To me your question suggests you are new to object-oriented programming ... nothing wrong with that ! Everybody here was "new" ... once Smile | :)

It's important you get a clear understanding of what the fundamental elements of .NET OOP are: Classes, Abstract Classes, Structs, Interfaces, Inheritance.

The best way to do this, imho, is to get a good book and study it carefully. Here are recommendations I have made that people have found useful:
[^], [^].

Some disciplined study ... and lots of experimentation ... will have a great value for you in the near future.

«While I complain of being able to see only a shadow of the past, I may be insensitive to reality as it is now, since I'm not at a stage of development where I'm capable of seeing it.» Claude Levi-Strauss (Tristes Tropiques, 1955)

OriginalGriff4-Jan-18 21:39

OriginalGriff

4-Jan-18 21:39

Ignore this specific example, and think more generally: how would you do this in the "real world"?
What information is there that is "single use" and associated with one individual? What information is shared by multiple individuals? And what information is multiply associated with a single individual?

Think about cars for a moment.
"Your car" is a specific vehicle: it has a unique registration, VIN number. But it shares it's manufacturer with many other vehicles, it's model with a large number of those, it's colour with a range of vehicles from other manufacturers, and it has a number of optional features associated with that specific vehicle.

So you have "single use" info: registration, VIN, owner.
"shared" info: manufacturer, model, colour.
"multiple" info: reversing camera, GPS system, leather interior.

So a Car class would need to have a way to contain that:

public class Car
    {
    public string Registration { get; set; }
    public string VIN { get; set; }
    public Manufacturer Manufacturer { get; set; }
    public Model Model { get; set; }
    public Color Color { get; set; }
    public List<Option> Options { get; set; }
    }

Your problem is the same thing: analyze the data you need to handle, and work out how you need to store it. With a bit of thinking, it should be pretty obvious what you need to do - so try it with several examples, and refine your model until it works with everything you can think of.

Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...
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listview to combobox - HELP

Member 136074164-Jan-18 10:31

4-Jan-18 10:31

Hi,
i need help.
How to when select item from listview from Form1 and click button, to open it Form2 and focus that item to combobox.

Thank you in advance !

Gerry Schmitz4-Jan-18 10:40

4-Jan-18 10:40

Why do you have a ListView and a ComboBox if they both contain the same items?

What's the point of switching forms if it's the same data? And the same "selected item"?

"(I) am amazed to see myself here rather than there ... now rather than then".
― Blaise Pascal

Member 136074165-Jan-18 12:32

5-Jan-18 12:32

In first Form are just name of users in listview, and in the other Form2 are all data from user(name, age ...) .
Witch code to get that select item form listview from Form1 switch to Form2 and focus in combobox.

Gerry Schmitz6-Jan-18 6:28

6-Jan-18 6:28

You have 2 "challenges":

1) Passing data between forms
2) And initializing a combobox.

And since all can be done in any number of ways, there is no easy answer.

For (1), it sounds like form1 creates form2, so pass the "selected name" to form2 in form2's constructor. Form1's "selection" is the .SelectedItem / item at .SelectedIndex in the listview.

In (2), initialize the combobox to the item with the "selected name" by locating it's index in the cb's itemsource; and set the .SelectedIndex to that.

(As I said, there are other ways; but you got to start somewhere).

"(I) am amazed to see myself here rather than there ... now rather than then".
― Blaise Pascal

Member 136074167-Jan-18 3:59

7-Jan-18 3:59

Something doesn't work.

This is database table:

CREATE TABLE [dbo].[Klijent] (
[klijentId] INT IDENTITY (1, 1) NOT NULL,
[naziv_klijenta] VARCHAR (50) NOT NULL,
[telefon] CHAR (15) NOT NULL,
PRIMARY KEY CLUSTERED ([klijentId] ASC)
);

Code Form1:

private void buttonPrikazi_Click(object sender, RoutedEventArgs e)
{
PostojeciKorisnik korisnik = new PostojeciKorisnik();
korisnik.itemForm1 = listViewPregled.SelectedItem.ToString();
korisnik.Show();
}

Code Form2:

public string itemForm1;

public PostojeciKorisnik(string item)
{
InitializeComponent();
this.itemForm1 = item;
}

private void Window_Loaded(object sender, RoutedEventArgs e)
{
comboBoxKlijent.Items.Add(itemForm1);
}

Gerry Schmitz7-Jan-18 7:10

7-Jan-18 7:10

Even with this little code, there's a lot going on. First, just get the "selected item".

The "selected item" depends on the "selected index".

if the selected index is not > -1, the selected item will be null. You need code to handle that.

Then you need to decide how you want to get the "name" to form 2.

You have a constructor, which you ignored; and set the property directyly instead. Works, but "why"?

Your combo box should already be loaded; you're just doing a "lookup"; and setting the selected index on the combo box.

Methinks you should have a better plan; a flow chart perhaps.

"(I) am amazed to see myself here rather than there ... now rather than then".
― Blaise Pascal

Mycroft Holmes4-Jan-18 12:44

Mycroft Holmes

4-Jan-18 12:44

Assuming you actually want to pass the selected item from form 1 to form 2 you do this in the click event of the button.

Try this Search

Never underestimate the power of human stupidity
RAH

Member 136074165-Jan-18 12:26

5-Jan-18 12:26

Yes, which code can this item from Form1 switch to Form2 and focus in combobox.

improve a recursive search method ?

Mycroft Holmes6-Jan-18 10:27

Mycroft Holmes

6-Jan-18 10:27

Did you even look at the results of the search? The article there will tell you how to achieve what you are hoping to do.

Never underestimate the power of human stupidity
RAH

BillWoodruff4-Jan-18 5:01

4-Jan-18 5:01

I set myself "coding challenges:" this is one of them.

The questions: how to "stop" the recursion without using an external boolean flag. Context: while I know how to write hierarchy-enumeration code using a Stack, for TreeViews and such, the "path-finding" problem, here, is running down the walls of my brain like warm honey Smile | :)

.. the code works, but it don't feel right. A bigger issue may be if the strategy I used to try and optimize the search ... via keeping track of "visited" values ... is accurate, robust, etc.

Using a generic Dictionary<T1, List<T1>> RDictT1T2; named 'test5 ... with these sample values:

var test5 = new Dictionary<string. List<string>>>();

test5.Add("a", new List<string>{"c", "d", "b" });

test5.Add("b", new List<string> { "c","f","g", "e" });

test5.Add("e", new List<string> { "g", "h", "k" });

test5.Add("k", new List<string> { "b", "l",});

I use the following code to get a possible "path" between one string value and another:

private List<T1> Result, Visited;
private T1 Start, Target;
private bool found = false;

public List<T1> FindPath(T1 start, T1 target)
{
    Result = new List<T1>();
    Visited = new List<T1>();

    Start = start;

    if (RDictT1T2[Start].Count == 0) return null;

    Target = target;

    Visited.Add(Start);
    Result.Add(Start);

    // check for direct linkage
    if (RDictT1T2.ContainsKey(Start) && RDictT1T2[Start].Contains(Target))
    {
        Result.Add(Target);
        return Result;
    }

    // recursion time
    found = false;
    return FindRecurse(Start);
}

private List<T1> FindRecurse(T1 rstart)
{
    foreach (var t1 in RDictT1T2[rstart])
    {
        if (Visited.Contains(t1)) 
        {
            continue;
        }
        else
        {
            if(
                !RDictT1T2.ContainsKey(t1)
                ||
                RDictT1T2[t1].Count == 0
              )
            {
                Visited.Add(t1);
                continue;
            }
        }

        Result.Add(t1);
        Visited.Add(t1);

        if (RDictT1T2[t1].Contains(Target))
        {
            Result.Add(Target);
            found = true;
        }
        else
        {
            FindRecurse(t1);
        }
    }

    return found ? Result : null;
}

These tests produce the expected results:

var r1 = test5.FindPath("a", "d"); // a d

var r2 = test5.FindPath("a", "f"); // a b f

var r3 = test5.FindPath("a", "k"); // a b e k

var r4 = test5.FindPath("k", "x"); // null

var r5 = test5.FindPath("k", "g"); // k b g

Gerry Schmitz4-Jan-18 10:02

4-Jan-18 10:02

I would have taken it one step further ... and built the actual "object graph"; which would be easier to traverse than probing a dictionary.

I use producedural code to build object graphs that can then be accessed "functionally" at run time.

"(I) am amazed to see myself here rather than there ... now rather than then".
― Blaise Pascal

BillWoodruff4-Jan-18 12:24

4-Jan-18 12:24

Gerry Schmitz wrote:
I use producedural code to build object graphs that can then be accessed "functionally" at run time.

I do too; it would be great to see an example of your code.

Message Closed

4-Jan-18 13:05

4-Jan-18 13:05

Message Closed

modified 5-Jan-18 2:47am.

Message Closed

4-Jan-18 20:10

4-Jan-18 20:10

Message Closed

modified 15-Jan-18 13:17pm.

Gerry Schmitz4-Jan-18 20:27

4-Jan-18 20:27

Sorry ... I thought it was a tree.

And sorry for boring you.

"(I) am amazed to see myself here rather than there ... now rather than then".
― Blaise Pascal

Richard Deeming8-Jan-18 5:55

Richard Deeming

8-Jan-18 5:55

Something like this seems to work:

public static IReadOnlyCollection<T> FindPath<T>(this IReadOnlyDictionary<T, IReadOnlyCollection<T>> nodes, T start, T target, IEqualityComparer<T> comparer = null)
{
    if (nodes == null) throw new ArgumentNullException(nameof(nodes));
    if (comparer == null) comparer = EqualityComparer<T>.Default;
    
    var prefix = new List<T> { start };
    return FindPathCore(start, prefix);

    IReadOnlyCollection<T> FindPathCore(T current, IReadOnlyCollection<T> pathToCurrent)
    {
        if (comparer.Equals(current, target))
        {
            return pathToCurrent;
        }
        if (nodes.TryGetValue(current, out var connections))
        {
            foreach (T node in connections.Except(pathToCurrent))
            {
                var path = new List<T>(pathToCurrent);
                path.Add(node);
                var result = FindPathCore(node, path);
                if (result != null) return result;
            }
        }
        
        return null;
    }
}

Test:

var test5 = new Dictionary<string, IReadOnlyCollection<string>>
{
    ["a"] = new List<string> { "c", "d", "b" },
    ["b"] = new List<string> { "c", "f", "g", "e" },
    ["e"] = new List<string> { "g", "h", "k" },
    ["k"] = new List<string> { "b", "l" },
};

test5.FindPath("a", "d").Dump(); // a d
test5.FindPath("a", "f").Dump(); // a b f
test5.FindPath("a", "k").Dump(); // a b e k
test5.FindPath("k", "x").Dump(); // null
test5.FindPath("k", "g").Dump(); // k b g

"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer

BillWoodruff15-Jan-18 6:01