LinkButton on GridView

[rnooraei]

Hi
I have the following code in my GridView, I would like to make my linkbutton visible or invisible (depend on action)
please see the following code

Dim CancelButton As LinkButton = CType(Me.grdContacts.FindControl("LinkButton_Cancel"), LinkButton)
Dim DeleteButton As LinkButton = CType(Me.grdContacts.FindControl("LinkButton_Delete"), LinkButton)
CancelButton.Visible = True
DeleteButton.Visible = False

but when I get to CancelButton.Visible = True , I get the following error message.
NullReferenceExeption was unhandled by user code
any help appreciated.
Thanks

 

[jbenson001]

What event is this code in? Is the FindControl() actually finding the control?

 

[jmeckley]

Assuming this is in the RowDataBound Event and assuming these controls are located within a TemplateField like this

<TemplateField>
    <ItemTemplate>
        <asp:Button ID="LinkButton_Delete" runat="server" ... />
    </ItemTemplate>
    <EditTemplate>
        <asp:Button ID="LinkButton_Cancel" runat="server" ... />
    </EditTemplate>
</TemplateField>

then

if e.Row.RowIndex > -1 Then
   Dim CancelButton As LinkButton = CType(Me.grdContacts.FindControl("LinkButton_Cancel"), LinkButton)
   If (Not CancelButton is Nothing) Then
      CancelButton.Visible = True
   End If

   Dim DeleteButton As LinkButton = CType(Me.grdContacts.FindControl("LinkButton_Delete"), LinkButton)
   If (Not DeleteButton is Nothing) Then
      DeleteButton .Visible = True
   End If
End If

when using templateFields selected controls are only rendered for a specific template (Item, Select, Edit) so depending on row state will effect which controls are available.

the RowIndex > -1 checks to make sure your not in the Header or Footer row.
you could also check the RowState and RowType if you don't want to use Indexes or Nothing checks. Just remember to Check for Item or AlternateItem if you go the non-index route.

Jason Meckley
Programmer
Specialty Bakers, Inc.

 

[rnooraei]

Hi
What is happen if I want to use in the other event

Protected Sub grdContacts_RowCommand(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewCommandEventArgs) Handles grdContacts.RowCommand
If e.CommandName = "Edit" Then
Dim CancelButton As LinkButton = CType(Me.grdContacts.FindControl("LinkButton_Cancel"), LinkButton)
Dim DeleteButton As LinkButton = CType(Me.grdContacts.FindControl("LinkButton_Delete"), LinkButton)
CancelButton.Visible = True
DeleteButton.Visible = False
End If

End Sub

 

[jmeckley]

if you use row command you have 2 options
1. get the row index the command was issued against.
2. cycle throug each row in the grid and preform the action.

personall this is the main purpose of the RowDataBound event. I would use that instead of the RowCommand event.

Jason Meckley
Programmer
Specialty Bakers, Inc.