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I have a page with two datagrids. One reads the value from a database and allows selection. When the user selects a grid it adds the data to the second datagrid. This is the code I am using for this:

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

    Dim dc1 As New DataColumn("NAME")
    Dim dc2 As New DataColumn("PRICE")
    dt.Columns.Add(dc1)
    dt.Columns.Add(dc2)
    Dim dr1 As DataRow = dt.NewRow()
    GridView2.DataSource = dt
    GridView2.DataBind()
End Sub

and

Protected Sub GridView1_SelectedIndexChanged(sender As Object, e As EventArgs) Handles GridView1.SelectedIndexChanged
        Dim dr1 As DataRow = dt.NewRow()

        dr1(0) = Name.ToString
        dr1(1) = Price.ToString
        dt.Rows.Add(dr1)
        GridView2.DataSource = dt
        GridView2.DataBind()

Now, this works perfectly.... but this obviously would work under a forms service. In a web based enviroment whenever a user selects a value in Grid 1 it resets the values in Grid 2 and I need that multiple rows are added to the 2nd Datagrid every time the user selects a value. The "data adding" is fired when the selectedindexchanged event takes place in GridView1. I think I need to save the data to a session/cookie but I have no idea how would I do this in the case of a datagrid. Like, what should I save and how I'd read it. Both Gridviews are under an Update Panel control so Postback should be instantaneous (if needed).

Sightly updated code...

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
    If Not IsPostBack Then
        dt = DirectCast(Session("Purchase"), DataTable)
    Else
        Dim dc1 As New DataColumn("NAME")
        Dim dc2 As New DataColumn("PRICE")
        dt.Columns.Add(dc1)
        dt.Columns.Add(dc2)
        Dim dr1 As DataRow = dt.NewRow()
        GridView2.DataSource = dt
        GridView2.DataBind()
    End If
End Sub

and

            Dim dr1 As DataRow = dt.NewRow()
        Session.Add("Purchase", dt)
        dr1(0) = Name.ToString
        dr1(1) = Price.ToString
        dt.Rows.Add(dr1)
        dt = DirectCast(Session("Purchase"), DataTable)
        GridView2.DataSource = dt
        GridView2.DataBind()
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  • You wouldn't save the datagrid in the session you would save the datatable and set the datasource of the datagrid to the datatable each time a record is added. Session.Add("Key", dt) to save it to the session and directcast(Session("Key"), datatable) to read it back. Commented May 14, 2013 at 18:25
  • I adjusted the code accordingly but still no go. I set this under Selectedindex changed Session.Add("Purchase", dt) after the dr1 is declared. Then in pageload I added this If Not IsPostBack Then dt = DirectCast(Session("Purchase"), DataTable) Else ... code. Still the same result. Am I doing it wrong? Commented May 14, 2013 at 18:48
  • can you edit your question with the updated code? Commented May 14, 2013 at 19:00
  • Updated the code Mike! Commented May 14, 2013 at 19:11

2 Answers 2

Reset to default
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Try this:

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
    'This will load the DT into the session when the page initially loads and then skip it on subsequent page loads.
    If Not IsPostBack Then
        Dim dc1 As New DataColumn("NAME")
        Dim dc2 As New DataColumn("PRICE")
        dt.Columns.Add(dc1)
        dt.Columns.Add(dc2)
        Session.Add("Purchase", dt)
        GridView2.DataSource = dt
        GridView2.DataBind()
    End If
End Sub

GridView1_SelectedIndexChanged:

'Clear out the old datasource.
GridView2.Datasource = Nothing
GridView2.DataBind()
'Pull the datatable from the session variable
dt = DirectCast(Session("Purchase"), DataTable)
'Create the new row and set the values
Dim dr1 As DataRow = dt.NewRow()
dr1(0) = Name.ToString
dr1(1) = Price.ToString
'Add the row to the table
dt.Rows.Add(dr1)
'If the session variable exists(which is should) then we overwrite it, if not we create it.
If Session("Purchase") Is Nothing Then Session.Add("Purchase", dt) Else Session("Purchase") = dt
'Reset the datasource of the datagrid
GridView2.DataSource = dt
GridView2.DataBind()

One thing I've run into doing this before is that in order for the datasource to actually update as expected I needed to do GridView2.Datasource = Nothing and GridView2.DataBind() as the very first thing in the event handler, I'm not sure why but it works when I do that and it doesn't when I don't so I didn't spend the time looking into it.

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3 Comments

Man just now I got it working with a very similar code. I deleted the page_load area altogether though, but this is even better and more detailed than my code. Thanks a million though! I updated my code with yours since this seems "classier". Love the comments as well.
I need to have a delete command each row. I've already done this in Design view but it doesn't (surprise!) do anything. How would I go programming the code behind? I already have the RowUpdating event but nothing works as I expect :P!
how are you thinking of implementing the delete? would the user select a row and click a button or what is the process they would go through?
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Seems to me like the problem is that when you select the first value, it creates a postback and that resets the other grid, you could disable EnableAutoPostback on your original element but i would like to know how are you manipulating the selected data.

I think you can easily accomplish this if instead of using 2 grids use one, add a column with a checkbox to grid named 'selected' and then save the selected row ids. Are you saving the selected rows to a database or how are you going to manipulate the selected rows? Another possibility is to use JQuery Drag and Drop (which in my opinion would be the most elegant solution but would require more time to code) with that, you can drag rows from one grid to another and then save the selected rows.

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1 Comment

Actually the idea is "kinda" like a cashier system. I first have, all under an Update Panel, three categories... Drinks, Food, Candy. The user selects one and the datagrid1 updates appropriately with the data from a table called products. Now, the user "Selects" (Adds to Cart) a product and it should display in a secondary datagrid where it shows what products he has added. Of course at the end I'll sum the values and it will give me a total. This is the best way I thought of :P! It doesn't need to be overly complex.

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