Help with streamwriter

**Branco Medeiros** · Mar 9 '07, 07:25 PM

Re: Help with streamwriter

pm wrote:
<backposted/>

To resize the array, you can either:

a) use Redim Preserve:

'assuming that NumRex has the new line count
Redim Preserve BookArray(0 To NumRex-1)

b) use some collection instead of an array. This way you don't need to
pre-fetch the lines to properly dim the array previouly to actually
filling it:

<aircode>
Dim Books As New List(Of Book)

'In your Load event:
Books.Clear
Do While oRead.Peek <-1
Dim Items() As String = oRead.ReadLine( ).Split(","c)
Dim NewBook As New Book
With NewBook
.BookId = CInt(Items(0))
.Title = Items(1)
.Author = Items(2)
.Publisher = Items(3)
.Datepublished = Items(4)
End With
Books.Add(NewBo ok)
Loop
oRead.Close
NumRex = Books.Count
</aircode>

Now, for adding a new record and saving it to the original file, you
can either

a) implement a "save all" functionality, where you'd overwrite the
original file with the current lines taken from the books:

<aircode>
'Create a backup and recover from errors is left as an exercise
Dim Out as New System.IO.Strea mWriter(STR_OUT FILE)
For Each B As Book in Books
Dim Line As String = String.Format(" {0},{1},{2},{3} ,{4}", _
B.BookId, B.Title, B.Author, _
B.Publisher, B.Datepublished )

Out.WriteLine(L ine)
Next
Out.Close
</aircode>

b) Open the file for appending and write just the new book:

<aircode>
Sub AddBook(NewBook As Book)
Books.Add(NewBo ok)
NumRex = Books.Count
Dim Out As Suystem.IO.Stre amWriter = _
System.IO.File. AppendText(STR_ OUTFILE)

Dim Line As String = String.Format(" {0},{1},{2},{3} ,{4}", _
NewBook.BookId, NewBook.Title, _
NewBook.Author, NewBook.Publish er, _
NewBook.Datepub lished)

Out.WriteLine(L ine)
Out.Close
End Sub
</aircode>

HTH.

Regards,

Branco.

hi
>
fairly new to vb.net . I have created a filesystem where a manager
and co workers hve limted access.
>
the manager can read members files. i have used streamreader to get
the details from a text file on my c drive into relevent text boxes eg
name, address by using arrays.
>
what i need to know is , how do i make it possible for the manager to
add a new record on the same page that will be appended to the same
text file on my c drive. and them read bak from it.
>
I also need to know how make my array bigger so say if there where
more records added.
>
any help gratfull- this is driving me mad
>
this is my code.
>
Public Class Form2
Public BookArray As Book() 'Class file
Public NumRex As Integer
Dim Current As Integer
>
Private Sub Form2_Load(ByVa l sender As System.Object, ByVal e As
System.EventArg s) Handles MyBase.Load
>
Dim datafile As String = "C:\BooksFile.t xt"
Dim oRead As New System.IO.Strea mReader(datafil e) ' Should
check that the file exists
Dim i As Integer = 0
Dim linein As String
Dim arr As String()
>
'Find out how many lines we've got
While oRead.Peek <-1
linein = oRead.ReadLine( )
i = i + 1
'MsgBox(linein & " i = " & i)
End While
NumRex = i - 1
'Redim ItemArray so it'll hold all the items
ReDim BookArray(NumRe x)
>
oRead.Close()
oRead = New System.IO.Strea mReader(datafil e)
>
For i = 0 To CastArray.Lengt h - 1
'Grab a line
linein = oRead.ReadLine( )
' Split the line at the commas and feed it into the arr
array
arr = linein.Split(", ")
'Now feed the elements of arr into the fields of
ItemArray(i)
BookArray(i) = New Book
BookArray(i).Bo okId = Int(arr(0))
BookArray(i).Ti tle = arr(1)
BookArray(i).Au thor = arr(2)
BookArray(i).Pu blisher = arr(3)
BookArray(i).Da tepublished = arr(4)
>
Next i
>
oRead.Close()
>
txtBookId.Text = BookArray(0).Bo okId
txtTitle.Text = BookArray(0).Ti tle
txtAuthor.Text = BookArray(0).Au thor
txtPublisher.Te xt = BookArray(0).Pu blisher
txtDatePublishe d.Text = BookArray(0).Da tepublished
Current = 0
>
Private Sub btnLastRecord_C lick(ByVal sender As System.Object, ByVal
e As System.EventArg s) Handles btnLastRecord.C lick
>
txtBookId.Text = BookArray(NumRe x).BookId
txtTitle.Text = BookArray(NumRe x).Title
txtAuthor.Text = BookArray(NumRe x).Author
txtPublisher.Te xt = BookArray(NumRe x).Publisher
txtDatePublishe d.Text = BookArray(NumRe x).Datepublishe d
Current = NumRex
>
Private Sub btnNextRecord_C lick(ByVal sender As System.Object, ByVal
e As System.EventArg s) Handles btnNextRecord.C lick
If Current < NumRex Then
Current = Current + 1
txtBookId.Text = BookArray(Curre nt).BookId
txtTitle.Text = BookArray(Curre nt).Title
txtAuthor.Text = BookArray(Curre nt).Author
txtPublisher.Te xt = BookArray(Curre nt).Publisher
txtDatePublishe d.Text = BookArray(Curre nt).Datepublish ed
>
End If
End Sub

Help with streamwriter

Help with streamwriter

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