Question

I have a gridview that contains value of every rows read from a text file. What I want to do is, edit and delete the selected row on the gridview. I already have the code to show every row on the textfile:

<asp:GridView ID="GVAnnouncement" runat="server" 
  AutoGenerateColumns="True" EmptyDataText="- No file saved -">
  <Columns>
    <asp:TemplateField HeaderText="No.">
      <ItemTemplate>
        <%# Container.DisplayIndex + 1%>
      </ItemTemplate>
    </asp:TemplateField>
  </Columns>
</asp:GridView>

On the Code Behind:

'''''Read every row then show it on gridview'''''

' Declarations  
Dim objStreamReader As New StreamReader(Server.MapPath("Announcement.txt"))
Dim arrText As New ArrayList

' Loop through the file and add each line to the ArrayList  
Do While objStreamReader.Peek() >= 0
    arrText.Add(objStreamReader.ReadLine)
Loop

' Close the reader  
objStreamReader.Close()

' Bind the results to the GridView  
GVAnnouncement.DataSource = arrText
GVAnnouncement.DataBind()

What I am going to ask is, how do I get the index of selected row return and fill the value to the textbox then update it to the textfile? Thank you very much.

Answer 1

One suggestion first: a file normally is not the best storage. You might consider to use a dbms instead.

If you want to edit/delete lines in a file, probably the easiest is to create all lines again.
You can store the index for example in a HiddenField.

<ItemTemplate>
    <asp:HiddenField runat="server" ID="HiddenIndex" Value="<%# Container.DataItem.Index %>" />
    <asp:Label ID="LblAnnouncement" Text="<%# Container.DataItem.Announcement %>" runat="server"></asp:Label>
</ItemTemplate>

Dim allAnnouncements = IO.File.ReadAllLines(Server.MapPath("Announcement.txt"))
Dim source = allAnnouncements.Select(Function(l, index) New With {.Index = index, .Announcement = l}).ToList

' Bind the results to the GridView  
GVAnnouncement.DataSource = source 
GVAnnouncement.DataBind()

Then you can edit/delete them in the following way:

Protected Sub GridView1_RowUpdated(ByVal sender As Object, ByVal e As GridViewUpdateEventArgs)  
    Dim grid = DirectCast(sender, GridView)
    Dim index = Int32.Parse(DirectCast(grid.Rows(e.RowIndex).FindControl("HiddenIndex"), HiddenField).Value)
    Dim oldAnnamouncement = e.OldValues(0).ToString
    Dim newAnnouncement = e.NewValues(0).ToString
    If Not oldAnnamouncement.Equals(newAnnouncement) Then
        Dim allAnnouncements = IO.File.ReadAllLines(Server.MapPath("Announcement.txt"))
        allAnnouncements(index) = newAnnouncement
        IO.File.WriteAllLines(Server.MapPath("Announcement.txt"), allAnnouncements)
    End If

    'Reset the edit index.
    GridView1.EditIndex = -1

    'Bind data to the GridView control.
    BindData()
End Sub



Protected Sub GridView1_RowDeleting(sender As Object, e As System.Web.UI.WebControls.GridViewDeleteEventArgs)
    Dim grid = DirectCast(sender, GridView)
    Dim index = Int32.Parse(DirectCast(grid.Rows(e.RowIndex).FindControl("HiddenIndex"), HiddenField).Value)

    Dim allAnnouncements = IO.File.ReadAllLines(Server.MapPath("Announcement.txt"))
    IO.File.WriteAllLines(Server.MapPath("Announcement.txt"), allAnnouncements.Where(Function(l, i) index <> i))

    'Bind data to the GridView control.
    BindData()
End Sub