Help draw twelve names without duplicate from txt file(code help)

I have a list of names in a txt files and i would like to have a code to draw randomly 12 names(or lines) without duplicate and put each in 12 combobox ( each combobox have a name(or line)
I am a beginner ,thank you to put a max of details.:)

The process to pick random items with no duplicates varies a little bit based on circumstances, but here's one that works:

1. Load every item in the file into a List.
2. Create an instance of the Random class.
3. Generate a random number between 0 and the list's Length -1.
4. Remove that item from the list and add it to a different list.
5. Repeat 3 and 4 until either the initial list is empty or the different list has 12 items.
6. Now the "different" list is 12 random items with no duplicates.

Try it out. If any of the steps are confusing, ask about them.

Quote:

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Originally Posted by Sitten Spynne

The process to pick random items with no duplicates varies a little bit based on circumstances, but here's one that works:

1. Load every item in the file into a List.
2. Create an instance of the Random class.
3. Generate a random number between 0 and the list's Length -1.
4. Remove that item from the list and add it to a different list.
5. Repeat 3 and 4 until either the initial list is empty or the different list has 12 items.
6. Now the "different" list is 12 random items with no duplicates.

Try it out. If any of the steps are confusing, ask about them.

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OK i understood but i need a code for the step 3 and step 4 .
please what mean random class.is a form?
thank for your smart answer

Here is an example of demonstrating Sitten's instructions:

Code:

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'Declare a new random object at the top-most level
Dim r As New Random

'Download the file into a collection
Dim lines() As String = IO.File.ReadAllLines("names.txt")

'Step1: Create a range of 0 to the length of the array
'Step2: Randomly order the array
'Step3: Take only 12 items from range
'Step4: Return the items from the lines array that match the index of the taken indices
Dim names() As String = (From i As Integer In enumerable.Range(0, lines.Length - 1) Order By r.Next() Take(12) Select lines(i)).ToArray()

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Fiddle: https://dotnetfiddle.net/ynkjmC

That LINQ can be a bit hard to understand. You can do the same thing with a loop and see the steps a bit more clearly:

Code:

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'Assuming the lines are in a List(of String) called NameSet;
'Also assuming that there are more than 12 names in the set.

Dim selectionSet As New List(of String)
Dim rand As New Random
Dim selectedName As String
For x = 0 to 11
  selectedName = NameSet(rand.Next(0,NameSet.Count))
  selectionSet.Add(selectedName)
Next

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That can be simplified by getting rid of selectedName, or can be simplified even further by using a single line LINQ statement as DDay showed. The loop can be easier when starting out, and will have superior performance, but either way will take less than a millisecond, so there isn't much difference.

Eh, I think that level of sophistication might lead to some interesting questions from whoever assigned this homework.

3-4 would look like this:

Code:

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Dim rng As New Random()
Dim randomNumber As Integer = rng.Next(0, 10)

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The Random class is used to generate random numbers. The Next() method, when used this way, will generate a number >= the first number and < the second number. That's a little weird, but the code above will generate a number between 0 and 9.

So let's say I have a list of 10 integers named '_items'. If I want to print three random items from the list, with possible duplicates:

Code:

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Dim rng As New Random()

For i As Integer = 1 To 3
    Dim randomIndex As Integer = rng.Next(0, _items.Count)
    Dim randomItem As Integer = _items(randomIndex)
    Console.WriteLine(randomItem)
Next

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It's important to NEVER call 'New Random()' inside a loop. If you do that, for technical reasons, you'll very likely see it give you the same numbers over and over again.

So your basic skeleton should look like this:

Code:

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Dim originalItems As new List(Of String)() ' I'm guessing String

' <Code to open the file and put all the items in _original items here>

Dim rng As New Random()
Dim randomItems As New List(Of String)()

For i As Integer = 1 To 12
    Dim randomIndex As Integer = rng.Next(0, _originalItems.Count)
    ' <add the item at that index to randomItems>
    ' <remove the item at that index from originalItems>
Next

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There's some blanks there for you to fill in, but if you get stuck or it doesn't work post what you tried and we'll explain what went wrong!

OK i understand a bit your reasoning. so i make a beginning with my problem.so we have this

Code:

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Dim lines() As String = IO.File.ReadAllLines(Application.StartupPath & "\DANfiles\charfighters.txt")' path of txt



        Dim selectionSet As New List(Of String)
        Dim rand As New Random
        Dim selectedName As String
        For x = 0 To 11
            selectedName = lines(rand.Next(0, lines.Count))
            selectionSet.Add(selectedName)
        Next
 ' i need put all selected names each one in a combobox different
' ex mark into combobox1, helen into combobox2,ect... to 12 combobox
' must i use a listbox?

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Could you add some lines to my code to complete this project. thank you

That doesn't make any sense. Putting all the names in one combobox (or a listbox) makes sense, but putting each name into a different combobox doesn't make any sense. The only thing you can do with a combobox is to choose an item once you drop it down. In this case, there will only be the one item to choose, so why bother dropping it down?

So, something is missing from that explanation. Is there other stuff that goes into the combobox? If so, what is it? Even if there is, I'd be wanting to put the names into labels above or beside the comboboxes.

Sorry, i just want to catch them separetely , i would have to say a label.:)

Yeah, a label would make more sense. A listbox would allow you to see them all, and sort them all (you can actually just call .Sort on selectionSet after it has been filled, if you want to Sort), and a listbox would be easier to extend. Putting twelve labels on the screen and assigning a different name to each one is possible, but becomes a chore if there is ever a thirteenth label added, or more. So, if you know it will always be 12, then labels do make sense, but if the number has any chance of changing, a Listbox would be easier.

Indeed ,the number stays 12 but 1.how retrieve my selectedname in a listbox 2 how transfer in a label( easy but i am beginner) thank you for you answer!

You can get the currently selected item in a ListBox by getting the Text property, from there simply assign the Text property of the ListBox to the Text property of the Label like this:

Code:

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Label1.Text = ListBox1.Text

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Quote:

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Originally Posted by dday9

You can get the currently selected item in a ListBox by getting the Text property, from there simply assign the Text property of the ListBox to the Text property of the Label like this:

Code:

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Label1.Text = ListBox1.Text

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OK but it is selectionset in a listbox,my problem is.( the list of random selection(12 names) in the listbox)how code it?

If you were to implement my code then it would look a little bit like this:

Code:

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Public Class Form1

    Private r As New Random
    Private Sub Form1_Load(ByVal sender As Object, ByVal e As EventArgs) Handles MyBase.Load
        Dim path As String = IO.Path.Combine(Application.StartupPath, "DANfiles", "charfighters.txt")
        Dim lines() As String = IO.File.ReadAllLines(path)
        Dim names() As String = (From i As Integer In enumerable.Range(0, lines.Length - 1) Order By r.Next() Take(12) Select lines(i)).ToArray()

        ListBox1.Items.AddRange(names)
    End Sub

    Private Sub ListBox1_SelectedIndexChanged(ByVal sender As Object, ByVal e As EventArgs) Handles ListBox1.SelectedIndexChanged
        If ListBox1.SelectedIndex <> -1 Then
            Label1.Text = ListBox1.Text
        Else
            Label1.Text = "N/A"
        End If
    End Sub
End Class

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