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Thread: listbox to richtextbox

  1. #1

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    Unhappy listbox to richtextbox

    Hi All. This is my first post here at VBForums.
    VB 2013. I have a listbox populated with .rtf files. When clicking a filename I want that file to show up in my richtextbox.
    I had it working in VB6 long time ago, but now I can not get it to work.
    Please help. It must be very simple.

    Here the listbox is populated with the specific .rtf files, and it work just fine.
    ListBox1.DataSource = IO.Directory.GetFiles("C:\MiniTanks\RTF", "*.rtf").Select(Function(file) IO.Path.GetFileName(file)).ToList

    Then the hard part, not working.
    Private Sub ListBox1_SelectedIndexChanged(sender As Object, e As EventArgs) Handles ListBox1.SelectedIndexChanged
    rtb3.LoadFile = ListBox1.SelectedItem.ToString()

    Please.
    My Best // Gert Persson, Malmö Sweden

  2. #2
    PowerPoster techgnome's Avatar
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    Re: listbox to richtextbox

    It's probably because LoadFile isn't a property, but a method.
    https://docs.microsoft.com/en-us/dot...System_String_

    Tad bit surprised VS didn't bark at you.

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  3. #3
    eXtreme Programmer .paul.'s Avatar
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    Re: listbox to richtextbox

    The problem also is ListBox1.SelectedItem is the filename. You need the full path

  4. #4

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    Re: listbox to richtextbox

    Thx for answering.

    This easy it was. Lol

    rtb3.LoadFile(FilPath + FilNamn)

  5. #5
    .NUT jmcilhinney's Avatar
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    Re: listbox to richtextbox

    I would suggest using DirectoryInfo instead of Directory. You can then get a list of FileInfo objects, which contain both name and path, to bind to your ListBox:
    vb.net Code:
    1. Dim folder As New DirectoryInfo("C:\MiniTanks\RTF")
    2. Dim files = folder.GetFiles("*.rtf")
    3.  
    4. With ListBox1
    5.     .DisplayMember = "Name"
    6.     .ValueMember = "FullName"
    7.     .DataSource = files
    8. End With
    then:
    vb.net Code:
    1. rtb3.LoadFile(CStr(ListBox1.SelectedValue))

  6. #6

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    Re: listbox to richtextbox

    Thanks for intresting code.
    I will test that code later.
    Best // Gert

  7. #7
    Super Moderator dday9's Avatar
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    Re: listbox to richtextbox

    Quote Originally Posted by jmcilhinney View Post
    vb.net Code:
    1. rtb3.LoadFile(CStr(ListBox1.SelectedValue))
    I think my eye slightly twitched a bit when I saw CStr.
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  8. #8
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    Re: listbox to richtextbox

    I think my eye slightly twitched a bit when I saw CStr.
    Lol, mine too. But I didn't want to poke the bear.

  9. #9
    eXtreme Programmer .paul.'s Avatar
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    Re: listbox to richtextbox

    ListBox1.SelectedValue is an Object containing a string. Hence the cast...

  10. #10
    .NUT jmcilhinney's Avatar
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    Re: listbox to richtextbox

    Quote Originally Posted by dday9 View Post
    I think my eye slightly twitched a bit when I saw CStr.
    Quote Originally Posted by wes4dbt View Post
    Lol, mine too. But I didn't want to poke the bear.
    LoadFile expects a String - requires a String with Option Strict On - and, as .paul. suggests, SelectedValue is type Object, because it can expose any type of object. As such, a cast or conversion is always required. Your choices would be:
    vb.net Code:
    1. rtb3.LoadFile(ListBox1.SelectedValue.ToString())
    2. rtb3.LoadFile(CType(ListBox1.SelectedValue, String))
    3. rtb3.LoadFile(CStr(ListBox1.SelectedValue))
    4. rtb3.LoadFile(DirectCast(ListBox1.SelectedValue, String))
    Personally, I NEVER call ToString on an Object reference that refers to a String. I keep that strictly for actual conversions from one type to another. DirectCast is actually the most correct here, because we are actually casting an Object reference to String as type String. Personally, I never use CType directly for anything. I either use DirectCast for a cast or some other method for a conversion, e.g. ToString or Convert.ToInt32. In cases like this one, I do use CType indirectly because it makes the code more succinct. That means that if I'm casting an Object reference to type String, Integer, Double, etc, then I will use CStr, CInt, CDbl, etc. In this case and those like it, the first two options above will work but I consider them less appropriate that the last two.

    In C#, I would write this:
    csharp Code:
    1. rtb3.LoadFile((string)ListBox1.SelectedValue);
    That is directly equivalent to the use of DirectCast in VB but, as I said, I use CStr and the like for brevity.

  11. #11
    Super Moderator dday9's Avatar
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    Re: listbox to richtextbox

    I would’ve called ToString, I didn’t consider DirectCast in this situation. It’s just the Microsoft.VisualBasic reference that caused the (very opinionated) twitch
    "Code is like humor. When you have to explain it, it’s bad." - Cory House
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  12. #12
    .NUT jmcilhinney's Avatar
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    Re: listbox to richtextbox

    Quote Originally Posted by dday9 View Post
    I would’ve called ToString, I didn’t consider DirectCast in this situation. It’s just the Microsoft.VisualBasic reference that caused the (very opinionated) twitch
    CStr has nothing to do with Microsoft.VisualBasic. It is a VB keyword, i.e. part of the VB language, which is why it turns blue in the code editor. Things like MsgBox, InStr, etc, are members of modules that are members of the Microsoft.VisualBasic namespace. There is no such module that CStr or CType or the like are part of. Note that calls to CStr, CType etc are actually inlined by the compiler, so they are more efficient than ToString as well.

    I guess that also begs the question, what would you have done if SelectedValue was exposing an ID of type Integer?

  13. #13
    Super Moderator dday9's Avatar
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    Re: listbox to richtextbox

    Quote Originally Posted by jmcilhinney View Post
    I guess that also begs the question, what would you have done if SelectedValue was exposing an ID of type Integer?
    Convert.ToInt32 has an object overload:
    Code:
    If (MyListBox.SelectedValue Is Nothing) Then
        Return ' or something meaningful
    End If
    
    Dim id = Convert.ToInt32(MyListBox.SelectedValue)
    "Code is like humor. When you have to explain it, it’s bad." - Cory House
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  14. #14
    .NUT jmcilhinney's Avatar
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    Re: listbox to richtextbox

    Quote Originally Posted by dday9 View Post
    Convert.ToInt32 has an object overload:
    Code:
    If (MyListBox.SelectedValue Is Nothing) Then
        Return ' or something meaningful
    End If
    
    Dim id = Convert.ToInt32(MyListBox.SelectedValue)
    So, again, that's converting something that is already an Int32 to an Int32. You should cast when you're changing the type of the reference only and convert when changing the type of the object.

  15. #15
    Fanatic Member Delaney's Avatar
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    Re: listbox to richtextbox

    On my side, when I tested you code, I used that :
    Code:
    CType(ListBox1.SelectedItem, IO.FileInfo).FullName
    so no need for a CStr or a .tostring. A bit different but work the same.
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  16. #16

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    Re: listbox to richtextbox

    Intresting discussion.
    Thx u all for spreding lights on this topics.
    Actually I only use this code.
    And that works just fine for me



    Private Sub Form2_Load(sender As Object, e As EventArgs) Handles MyBase.Load, MyBase.CursorChanged
    ListBox1.DataSource = IO.Directory.GetFiles("C:\MiniTanks\RTF", "*.rtf").Select(Function(file) IO.Path.GetFileName(file)).ToList
    End Sub

    Private Sub ListBox1_SelectedIndexChanged(sender As Object, e As EventArgs) Handles ListBox1.SelectedIndexChanged

    Dim FilNamn As String
    Dim FilPath As String

    FilPath = "C:\MiniTanks\RTF"
    FilNamn = (ListBox1.SelectedItem.ToString())

    rtb3.LoadFile(FilPath + FilNamn)

    End Sub
    I'm Swedish so FileName is FilNamn
    and FilePasth is FilPath

    And that works fine.
    In VB6 there was a FileList control as well as DirectoryList and Drive List.

    Thx ALL for contribute to this thread.
    Next broblem I have is about the DataGridView.
    Will start a new tread about it. Welcome to spread light on that topic too. Lol

    My Best // Gert Persson, Malmö Sweden

  17. #17
    Super Moderator dday9's Avatar
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    Re: listbox to richtextbox

    You're Swedish? I love y'all's fish.

    (this is a pun, it goes by pastellfiskar in your neck of the woods)
    "Code is like humor. When you have to explain it, it’s bad." - Cory House
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  18. #18

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    Re: listbox to richtextbox

    I dont get that dday9.

  19. #19
    eXtreme Programmer .paul.'s Avatar
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    Re: listbox to richtextbox

    Try this.

    instead of...

    Code:
    ListBox1.SelectedItem.ToString()
    Use...

    Code:
    ListBox1.Text

  20. #20
    .NUT jmcilhinney's Avatar
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    Re: listbox to richtextbox

    Quote Originally Posted by Delaney View Post
    On my side, when I tested you code, I used that :
    Code:
    CType(ListBox1.SelectedItem, IO.FileInfo).FullName
    so no need for a CStr or a .tostring. A bit different but work the same.
    Writing code to use CType so that you don't have to use CStr is achieving nothing because, as I mentioned in post #10, CStr, CInt and the like are simply shortcuts to using CType, to make the code more succinct. You've succeeded only in making the code more complex and reduced the effectiveness of the data-binding.

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