Vb .net .dat file probelm

Ziycon

im able to write to the .dat file but if i go to add another line it just over writes the fist line so it will only ever have one line in the .dat file, how do i get app to move to the end of file and then add the new line to the .dat file?

Private Sub cmdSaveClient_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdSaveClient.Click
Dim Main As New frmMain
Dim str As String = ""
Dim loc As String = "e:\client.dat"
Dim binWriter As New IO.BinaryWriter(IO.File.OpenWrite(loc))
If (txtNewClientName.Text <> " ") And (txtNewClientSource.Text <> " ") Then
MsgBox("Make sure all fields have been filled.", vbExclamation, "Warning")
Else
binWriter.Write(txtNewClientName.Text)
binWriter.Close()
Me.Hide()
Main.Show()
End If
End Sub

Mutant_Fruit

isn't there an append mode for appending to a file?

Ziycon

not sure, i'll look into it now, thanks.

bonkey

Yeah...either open for append (instead of for write), or don't open/close the file on every click, but rather open it (on first click / on form load / ???) and then keep it open until the form unloads or some other 'single occurrence' event.

The latter (keep-open) approach is often not the ideal, for a number of reasons, but it is an option to consider. Append is more likely to be your friend though.

jc

Ziycon

do u mean like:

binWriter.Append(txtNewClientName.Text)

i tried this but append is not an option for the Binary writer, its saying this are the only ones u can use:

binWriter.

options:
BaseStream
Close
Flush
GetType
Null
Seek
Write

mewso

Something like this might work:-

Dim loc As String = "e:\client.dat"
Dim fs As New IO.FileStream(loc, IO.FileMode.Append)
Dim binWriter As New IO.BinaryWriter(fs)

bonkey

http://www.devx.com/dotnet/Article/6971/0/page/2

Ziycon

thanks for everyones help, i got the reading and writing working to a .dat file!

One last question, i know the vbNewLine moves the curstor to thxt line, is there a way when you delete a row to move up one line?

stevenmu

Binary files don't really have the same concept of 'lines' that text files would, they're just a stream of data you can probably use 'seek' to go back to a certain point, but you'd have to figure out what point yourself.

Looking at the data you're putting out, it may make more sense for you to use a text file instead of a binary one (or maybe even XML ?). On the other hand I don't think text files support seek, to delete a line you have to read all lines up to that point, empty the whole file and write them back out again.

Maybe I'm wrong on that, I'm sure someone can correct me if so.