Deleting records from files

T

torg

Regular
Joined
Nov 7, 2002
Messages
60
Location
Norway
Thought I had solved the problem but oh...no

My problem is I want to delete an Item from the Listbox and therat deleting the corresponding value in the file, What am I doing wrong? Is it possible to remove entries from a file without having to delete files? What about System.IO.file.copy....?
eg:
If the items in the listbox is as follows:
Donald
Duck
Mickey
Mouse

And If I selects Mouse to remove, the data in the file look like:
Donald. (Everyone but one record is deleted)

I want it to look like this after deleting one record:
Donald
Duck
Mickey

Im inserting Items in a listbox from a textbox( txtPosts) in order to save the Items to a file. I`ve also got a button btnInsert and btnRemov.

Visual Basic: 
####Assuming Imports System.IO#### 

'In formloadprocedure i have the following code: 
Private Sub Instillinger_Load..... 
 If Not File.Exists("Data.txt") Then 
            Dim writerAs StreamWriter = File.CreateText("Data.txt") 
            writer.Close() 
        End If 

             Dim ReaderAs StreamReader = File.OpenText("Data.txt") 
        Do While ReaderAs .Peek <> -1 
            ListBox1.Items.Add(leser.ReadLine) 
        Loop 

        leser.Close() 
        TabControl1.Dock = DockStyle.Fill 
end sub 

private sub Insert 
Dim WriterAs StreamWriter = File.AppendText("Data.txt") 
         ListBox1.Items.Add(txtPosts.Text) 

        Writer.WriteLine(ListBox1.Items.Item(ListBox1.Items.Count - 1)) 
        Writer.Close() 

        txtPosts.Text = "" 
        txtposts.Focus() 
end sub 

private sub remove 
If Not File.Exists("Data.txt") Then 
            File.CreateText("Data.txt") 
        End If 

        Dim Writer As StreamWriter = File.CreateText("Temp.txt") 
        ListBox1.Items.Remove(ListBox1.SelectedItem) 
        Try 
            Writer.WriteLine(ListBox1.Items.Item(ListBox1.Items.Count - 1)) 
            Writer.Close() 
        Catch x As Exception 
        End Try 

        File.Delete("Data.txt") 
        File.Move("Temp.txt", "Data.txt")
 
On first glance, it looks like your remove method is just writing one item back to the list. The easy way would be after an item is deleted to loop through the list of remaining items, writing each one to the file. You shouldn't have to create the Temp file either.
 
What I thought I had done with my code was to delete one item from The listbox, then write all the remaining Items in the listbox to a file.. But here is the problem. I obviously don`t . Therefore I don`t follow your instructions. Could you demonstrate with a codeexample? :):)
 
Just put your current writeline inside the Remove method in a loop. If this doesn't work, post your project and I'll take a look.
Visual Basic: 
 Dim Writer As StreamWriter = File.CreateText("Temp.txt") 
'Here you're removing the item.
        ListBox1.Items.Remove(ListBox1.SelectedItem) 
        Try 
'I think you'd be alright if you just put this in a loop of *all*
' the remaining items.  
 Dim i As Integer
For i = 0 To ListBox1.Items.Count - 1
            Writer.WriteLine(ListBox1.Items.Item(i)) 
Loop
        Catch x As Exception 

        Finally
                Writer.Close() 
        End Try
 
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