[RESOLVED] [2005] Adding item once

[Pac_741]

Hi to all,

My situation is: Im working on a webbrowser project, i created a favorites toolbar, but i didnt know how to create the custom item that has a value and a displayname kinda property, so i asked in this forum, i got help so what i have so far its this :

This its the custom class that will contain the url and the webpage name

Public Class WebPageInfo
 
  Private _title As String
    Private _url As String
    Public Property Title() As String
        Get
            Return Me._title
        End Get
        Set(ByVal value As String)
            Me._title = value
        End Set
    End Property
    Public Property Url() As String
        Get
            Return Me._url
 
        End Get
        Set(ByVal value As String)
            Me._url = value
        End Set
    End Property
    Public Sub New(ByVal title As String, ByVal url As String)
        Me._title = title
        Me._url = url
    End Sub
End Class

Okay, thats my webpageinfo class,

Dim pageinfos As New System.ComponentModel.BindingList(Of WebPageInfo)
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Me.BindingSource1.DataSource = Me.pageinfos
        Me.ListBox1.DisplayMember = "Title"
        Me.ListBox1.ValueMember = "Url"
        Me.ListBox1.DataSource = Me.BindingSource1
    End Sub

Here comes my question.

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
 Me.pageinfos.Add(New WebPageInfo(WebBrowser1.DocumentTitle, WebBrowser1.Url.ToString))
    End Sub

In this event i would like to add the new item created just ONCE but i dont know how to, i have an idea of how it could be done, can someone give me clues on how to do this ? thanks

my idea its something like this :

Dim n as object
for each n in pageinfos 
Dim once as integer
once=listbox1.findstring(listbox1.displaymember) 
if (once=-1) then
                Me.pageinfos.Add(New WebPageInfo(WebBrowser1.DocumentTitle, WebBrowser1.Url.ToString))

it could be something like that, right ?

Thanks for your help

[jmcilhinney]

As I already posted in your other thread, ListBox.FindString will find the index of the first item that starts with the specified value. What values is the ListBox displaying? It's displaying the titles of the Web pages, so should you not be passing the title of the current Web page to FindString to determine whether it's already there?

Also, I think FindStringExact would be a better option as you don't care whether some other, different Web page happens to start with the same title.

To be the "most correct" you can be you should not be comparing the result to -1 either. As the documentation says, ListBox.NoMatches is returned if no matches are found:

If Me.ListBox1.FindStringExact(someValue) <> ListBox.NoMatches Then
    'Add the new value.
End If

[Pac_741]

what value do i have to set ?

pageinfos ?

[jmcilhinney]

This is a very simple concept and I don't think you're actually engaging your brain here. Consider this. You are keeping a list of people who are in your club. The list contains the names of the people. If a person comes to you and asks to join your club, what are you going to do? Would you ask them their name and then check the list to see if that name was already there? I think it highly likely.

Now, you've got a ListBox that is displaying Web page titles. You've now got a new Web page that you want to add. What are you going to do to see whether that Web page is already on the list?

One last clue. If you had a list of people's names you would check the list for a person's name. If you had a list of Web pages' titles you will check the list for a ___ ____'s _____.

That is all I'm going to say because I'm here to help people become better programmers and thinking for them does not achieve that aim.

[FourBlades]

Could we play hangman?
Is there an "S"?

[Pac_741]

This is a very simple concept and I don't think you're actually engaging your brain here. Consider this. You are keeping a list of people who are in your club. The list contains the names of the people. If a person comes to you and asks to join your club, what are you going to do? Would you ask them their name and then check the list to see if that name was already there? I think it highly likely.

Now, you've got a ListBox that is displaying Web page titles. You've now got a new Web page that you want to add. What are you going to do to see whether that Web page is already on the list?

One last clue. If you had a list of people's names you would check the list for a person's name. If you had a list of Web pages' titles you will check the list for a i know that i have to search a webpage name in the list

That is all I'm going to say because I'm here to help people become better programmers and thinking for them does not achieve that aim.

I understand it in words, but i cant translate it into code..


Lets see, I have a list that contains the webpage names thats = to pagesinfo, right ? or Listbox1.DisplayMember ?

then i have a listbox that displays the names in the displaymember property, right ?

so if thats so, i think i have to do this :

jmcilhinney, im sorry if you are loosing ur patience with me, but im new in the world of programming......

if i have to search in displaymember its :

dim s as string=listbox1.displaymember 
if listbox1.findstringexact(s) <> listbox.nomatches then
pageinfos.add(new webpageinfo(webbrowser1.DocumentTitle, webbrowser1.url.tostring)
end if

if i have to search in pageinfos i dont know how to

[jmcilhinney]

Look at the code that you just posted. You are creating a new WebPageInfo object like this:

new webpageinfo(webbrowser1.DocumentTitle, webbrowser1.url.tostring)

Now, if you add that WebPageInfo to the ListBox what value will get displayed? Will it be webbrowser1.DocumentTitle perhaps? So is that not the value you should be looking for? How many times can I say "the title of the Web page"?

[Pac_741]

Thanks, now i now im looking for the Webbrowser1.documenttitle, so is this the code i must use ? or theres something i have to change ?

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim s As String = WebBrowser1.DocumentTitle
        For Each s In ListBox1.DisplayMember
            If ListBox1.FindStringExact(s) <> ListBox.NoMatches Then
                pageinfos.Add(New WebPageInfo(WebBrowser1.DocumentTitle, WebBrowser1.Url.ToString))
            End If
        Next
        End Sub

[Pac_741]

Finally!! i got it !!

Dim n As Integer
        n = ListBox1.FindString(WebBrowser1.DocumentTitle)
        If (n = -1) Then
            pageinfos.Add(New WebPageInfo(WebBrowser1.DocumentTitle, WebBrowser1.Url.ToString))
        End If

[jmcilhinney]

I made the mistake of post "<>" instead of "=" earlier but it should be a simple substitution:

If Me.ListBox1.FindStringExact(Me.WebBrowser1.DocumentTitle) = ListBox.NoMatches Then
    'Add the new value.
    Me.pageInfos.Add(New WebPageInfo(Me.WebBrowser1.DocumentTitle, Me.WebBrowser1.Url.ToString()))
End If

Not that your code is wrong but that's more succinct and more correct. The 'n' variable is useless and,as I said, you should compare against ListBox.NoMatches rather than -1.

[Pac_741]

Thanks!