ASP VB.NET: GridView Dynamic Link Buttons Event Handling

[lilOlMe]

Hi there!

I have generated a GridView that looks something like:

SportName| CompanyNameX |CompanyNameY |CompanyNameZ
Hockey.....| Shipping------------ |Accounting-------- |Shipping------------
BaseBall...| Receiving-----------|Shipping------------|Accounting---------
Etc............| Accounting----------|Receiving---------- |Receiving-----------

Where there are an unknown number of Company Names and an unknown number of Sport Names....these are dynamically generated based on a database.

I've added link buttons to each of the Department Names.
When these are clicked I need to be able to pull up details on the department based on the Company Name and the Sport Name and display them in a panel below the GridView.

My problem is that I have no idea how to handle the link button clicks.
I've created a Template Class to convert the data to be displayed in the GridView into Link buttons...here's a quick snippet

Private Sub DisplayGV()
   Dim dv As DataView = CreateDataSource()
   myGV.DataSource= dv
   For i As Integer = 0 To dv.Table.Columns.Count -1
        Dim tf As New TemplateField
        tf.ItemTemplate = New GridViewClickableTemplate(DataControlRowType.DataRow, _
                _dv.Table.Columns(i).ColumnName)
            tf.HeaderTemplate = New GridViewClickableTemplate(DataControlRowType.Header, _dv.Table.Columns(i).ColumnName)
         myGV.Columns.Add(tf)
    Next
    myGV.DataBind()
 
End Sub
 
 
 Private Class GridViewClickableTemplate
        Implements ITemplate
        Private _templateType As DataControlRowType
        Private _columnName As String
 
        Sub New(ByVal type As DataControlRowType, ByVal colname As String)
            _templateType = type
            _columnName = colname
 
        End Sub
 
  Public Sub InstantiateIn(ByVal container As System.Web.UI.Control) Implements System.Web.UI.ITemplate.InstantiateIn
            Select Case _templateType
                Case DataControlRowType.Header
                    Dim headerText As New Label
                    headerText.Text = _columnName
                    container.Controls.Add(headerText)
                Case DataControlRowType.DataRow
                    Dim lnkBtn As New LinkButton
                    AddHandler lnkBtn.DataBinding, AddressOf Me.BindLinkButtons
 
                    container.Controls.Add(lnkBtn)
                Case Else
            End Select
        End Sub
 
Private Sub BindLinkButtons(ByVal sender As Object, ByVal e As EventArgs)
            Dim lnkBtn As LinkButton = CType(sender, LinkButton)
            Dim row As GridViewRow = CType(lnkBtn.NamingContainer, GridViewRow)
            Dim content As String = DataBinder.Eval(row.DataItem, _columnName).ToString
            lnkBtn.Text = content
            If String.Compare(content, "Shipping") = 0 Then
                lnkBtn.CssClass = "red"
                lnkBtn.CommandName = "DisplayInfo"
                lnkBtn.CommandArgument = 1
            ElseIf String.Compare(content, "Accounting") = 0 Then
                lnkBtn.CssClass = "green"
                lnkBtn.CommandName = "DisplayInfo"
                lnkBtn.CommandArgument = 2
            ElseIf content.StartsWith("Receiving") Then
                lnkBtn.CssClass = "blue"
                lnkBtn.CommandName = "DisplayInfo"
                lnkBtn.CommandArgument = 3
            End If
        End Sub
End Class
 

I have a sub named DisplayInfo and would have assumed that the CommandName would link the link buttons to this command:

Protected Sub DisplayInfo (ByVal sender As Object, ByVal e As EventArgs)
        Dim lnkBtn As LinkButton = CType(sender, LinkButton)
        DisplayTheStuff(lnkBtn.CommandArgument)
    End Sub
 

However DisplayInfo is never reached...

How do you handle dynamically created link buttons in a GridView through one event handler?

Thanks

-LilOlMe

[nateraaaa]

I think you will need to use the RowCommand event of the GridView to accomplish what you are trying to do. In this event you should be able to check the value of CommandName using GridViewCommandEventArgs e parameter. Give this a try and let us know if you get stuck on something.

Nathan

[lilOlMe]

I think you will need to use the RowCommand event of the GridView to accomplish what you are trying to do. In this event you should be able to check the value of CommandName using GridViewCommandEventArgs e parameter. Give this a try and let us know if you get stuck on something.

Nathan

The RowCommand event did not fire.

[nateraaaa]

The RowCommand event did not fire.

Do you have the RowCommand event wired up for the GridView? You can right click the GridView in Design View and click Properties then click the lightning bolt at the top of the properties window. Now double click on the RowCommand event. This will create the event in your code behind file. Set a breakpoint in the Page_Load event and also in the RowCommand event. Tell me where your breakpoint hits after the Page_Load event.

Nathan

[lilOlMe]

Do you have the RowCommand event wired up for the GridView? You can right click the GridView in Design View and click Properties then click the lightning bolt at the top of the properties window. Now double click on the RowCommand event. This will create the event in your code behind file. Set a breakpoint in the Page_Load event and also in the RowCommand event. Tell me where your breakpoint hits after the Page_Load event.

Nathan

It doesn't hit a break point after the Page_Load break point.

   <asp:GridView ID="MyGV" runat="server" CellPadding="4" 
              BorderColor="Black" BorderWidth="1" GridLines="both"
              ForeColor="#333333" PagerSettings-Position=top
              allowpaging=true PageSize=10 PagerSettings-Mode=NumericFirstLast
              autogeneratecolumns="false"
              onrowcommand="MyGV_RowCommand">
 
                 <FooterStyle BackColor="#104E8B" Font-Bold="True" ForeColor="White" />
                 <RowStyle BackColor="#F7F6F3" ForeColor="#333333" />
                 <PagerStyle BackColor="#5D7B9D" ForeColor="White" HorizontalAlign="Center" />
                 <HeaderStyle BackColor="#104E8B" Font-Bold="True" ForeColor="White" />
            </asp:GridView>   
 

    Protected Sub MyGV_RowCommand(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewCommandEventArgs) Handles MyGV.RowCommand
        Dim lnkBtn As LinkButton = CType(sender, LinkButton)
        ShowDetails(lnkBtn.CommandArgument)
    End Sub
 

[lilOlMe]

I've had something similar happen once before...when I had given more than one ListItem the same Value property in a DropDownList....the SelectedIndexChanged never fired in that case.

I don't know why it would seem to be the same problem with LinkButtons though, each of them has a unique name, the CommandName and the Arguments may be duplicated...but the are individual LinkButtons...so I'm not sure it's the same problem.

Thanks a lot for your help...it's greatly appreciated.
-LilOlMe

[nateraaaa]

Try using the e parameter of the RowCommand event to assign the parameter value of ShowDetails.

ShowDetails(e.CommandArgument);

Nathan

[lilOlMe]

1. <LI style="FONT-SIZE: 8pt; BACKGROUND: #fcfcfc">[font='Courier New', Courier, monospace] [/font]

[font='Courier New', Courier, monospace]Try changing your RowCommand event to use the GridViewCommandEventArgs parameter.[/font]
[font='Courier New', Courier, monospace] [/font]

1. <LI style="FONT-SIZE: 8pt; BACKGROUND: #fcfcfc">[font='Courier New', Courier, monospace]Protected [color=#0600ff]Sub[/color] MyGV_RowCommand[color=#000000]([/color][color=#ff8000]ByVal[/color] sender [color=#ff8000]As[/color] [color=#ff0000]Object[/color], [color=#ff8000]ByVal[/color] e [color=#ff8000]As[/color] System.[color=#0000ff]Web[/color].[color=#0000ff]UI[/color].[color=#0000ff]WebControls[/color].[color=#0000ff]GridViewCommandEventArgs[/color] [color=#000000])[/color] [color=#ff8000]Handles[/color] MyGV.[color=#0000ff]RowCommand[/color][/font]
   <LI style="FONT-SIZE: 8pt; BACKGROUND: #fcfcfc">[font='Courier New', Courier, monospace] ShowDetails[color=#000000](e[/color].[color=#0000ff]CommandArgument[/color][color=#000000])[/color][/font]
2. [font='Courier New', Courier, monospace] [color=#0600ff]End[/color] [color=#0600ff]Sub[/color][/font]

[font='Courier New', Courier, monospace][color=#0600ff]Nathan[/color][/font]

I don't understand....
Could you please repost?

[lilOlMe]

This really isn't a "Row Command" that I'm issuing
I'm issuing a LinkButton to mimic what I would call a "Cell Command"......

Each Cell contains a LinkButton (not ButtonFields...)

Seeing as the RowCommand Event is not fired when I click these link buttons, I'm still wondering how to capture the click events for each of these link buttons.

There's a Lot of them:
There can be 2 - 40 columns, and 1-511 rows....that's a lot of link buttons...
up to (40 X 511) 20440 link buttons.
<edit> correction: there can only be 40X10 at one time because the GridView pages...so 400 link buttons...still a lot</edit>

I just need to check the value of the cell that's been selected...Just need to check the Command Argument of the specific link button clicked.

[lilOlMe]

I solved the problem...though it feels like somewhat of a workaround.
I never did get the RowCommand event to fire.

When I converted the GridView's content into LinkButtons I added a JavaScript call:

Private Sub BindLinkButtons(ByVal sender As Object, ByVal e As EventArgs)
           Dim lnkBtn As LinkButton = CType(sender, LinkButton)
           Dim row As GridViewRow = CType(lnkBtn.NamingContainer, GridViewRow)
            Dim content As String = DataBinder.Eval(row.DataItem, _columnName).ToString
            lnkBtn.Text = content
            If String.Compare(content, "Shipping") = 0 Then
                lnkBtn.CssClass = "red"
                lnkBtn.Attributes.Add("onclick", "javascript:SetDisplayCode('0');")
            ElseIf String.Compare(content, "Accounting") = 0 Then
                lnkBtn.CssClass = "green"
                lnkBtn.Attributes.Add("onclick", "javascript:SetDisplayCode('255');")
            ElseIf content.StartsWith("Receiving") Then
                lnkBtn.CssClass = "blue"
                lnkBtn.Attributes.Add("onclick", "javascript:SetDisplayCode('2');")
            End If
End Sub
 

The JavaScript function sets a hidden field with the "display code" and I check that in the PageLoad and automatically display the thing that needs to be displayed.

Thanks again for your help!

-LilOlMe