Dinamically created checkboxes, event handler and more - vb.NET asp.NET - asp.net

Question

I'm trying to manage the checkall control in a gridview but I'm facing several problems.
This is my gridview control:
<asp:GridView ID="gvShow" runat="server" AutoPostback="True" AllowPaging="True" AllowSorting="True" AutoGenerateColumns="False" Height="224px" HorizontalAlign="Center" Width="761px" CellPadding="4" ForeColor="#333333" DataSourceID="sid_db">
<AlternatingRowStyle BackColor="White" ForeColor="#284775" />
<Columns>
<asp:TemplateField ItemStyle-Width="50px">
<HeaderTemplate>
<asp:CheckBox ID="chkCheckAll" runat="server" AutoPostBack="False" OnCheckedChanged="chkCheckAll_CheckedChanged" />
</HeaderTemplate>
<ItemTemplate>
<asp:CheckBox ID="chkCheck" runat="server" />
</ItemTemplate>
<ItemStyle Width="50px"></ItemStyle>
</asp:TemplateField>
<asp:BoundField DataField="Scope" HeaderText="Scope" SortExpression="Scope" />
<asp:BoundField DataField="Brand" HeaderText="Brand" SortExpression="Brand" />
<asp:BoundField DataField="Site ID" HeaderText="Site ID" SortExpression="Site ID" />
<asp:BoundField DataField="Site Name" HeaderText="Site Name" SortExpression="Site Name" />
<asp:BoundField DataField="Address" HeaderText="Address" SortExpression="Address" />
<asp:BoundField DataField="CAP" HeaderText="CAP" SortExpression="CAP" />
<asp:BoundField DataField="City" HeaderText="City" SortExpression="City" />
<asp:BoundField DataField="Country" HeaderText="Country" SortExpression="Country" />
<asp:BoundField DataField="Master_ID" HeaderText="Master_ID" SortExpression="Master_ID" ItemStyle-CssClass="hiddencol" HeaderStyle-CssClass="hiddencol">
<HeaderStyle CssClass="hiddencol"></HeaderStyle>
<ItemStyle CssClass="hiddencol"></ItemStyle>
</asp:BoundField>
</Columns>
<EditRowStyle BackColor="#999999" />
<FooterStyle BackColor="#5D7B9D" Font-Bold="True" ForeColor="White" />
<HeaderStyle BackColor="#5D7B9D" Font-Bold="True" ForeColor="White" />
<PagerStyle BackColor="#284775" ForeColor="White" HorizontalAlign="Center" />
<RowStyle BackColor="#F7F6F3" ForeColor="#333333" />
<SelectedRowStyle BackColor="#E2DED6" Font-Bold="True" ForeColor="#333333" />
<SortedAscendingCellStyle BackColor="#E9E7E2" />
<SortedAscendingHeaderStyle BackColor="#506C8C" />
<SortedDescendingCellStyle BackColor="#FFFDF8" />
<SortedDescendingHeaderStyle BackColor="#6F8DAE" />
</asp:GridView>
First problem:
The checkbox controls are dynamically created and I honestly have the feeling that I should create an event handler for those, but I don't know how to do it nor I know where to put/write that code. I just see those controls are not recognized once I try to reference them in my code.
Second problem:
Since I'm pretty much a newbie, I made a step back and tested with some junk code if I was able to have all the checkboxes dinamically checked at page load... here is my test... the result a complete failure, nothing happens. I even tried to put the code in the init event, but the result is the same.
For Each row As GridViewRow In gvShow.Rows
DirectCast(row.FindControl("chkCheck"), CheckBox).Checked = True
Next
I would be grateful if anyone could help me with these problems.
Thanks in advance for your time.
Regards,

Answer 1

I have found the answer myself. I had to change the code as follow:
<asp:GridView ID="gvShow" runat="server" AllowPaging="True" AllowSorting="True" AutoGenerateColumns="False" Height="224px" HorizontalAlign="Center" Width="761px" CellPadding="4" ForeColor="#333333">
<AlternatingRowStyle BackColor="White" ForeColor="#284775" />
<Columns>
<asp:TemplateField ItemStyle-Width="50px">
<HeaderTemplate>
<asp:CheckBox ID="ChkSelectAll" runat="server" Autopostback="True" OnCheckedChanged="ChkSelectAll_CheckedChanged" />
</HeaderTemplate>
<ItemTemplate>
<asp:CheckBox ID="ChkSigleItem" runat="server" OnCheckedChanged="ChkSigleItem_CheckedChanged" />
</ItemTemplate>
<ItemStyle Width="50px"></ItemStyle>
</asp:TemplateField>
<asp:BoundField DataField="Scope" HeaderText="Scope" SortExpression="Scope" />
<asp:BoundField DataField="Brand" HeaderText="Brand" SortExpression="Brand" />
<asp:BoundField DataField="Site ID" HeaderText="Site ID" SortExpression="Site ID" />
<asp:BoundField DataField="Site Name" HeaderText="Site Name" SortExpression="Site Name" />
<asp:BoundField DataField="Address" HeaderText="Address" SortExpression="Address" />
<asp:BoundField DataField="CAP" HeaderText="CAP" SortExpression="CAP" />
<asp:BoundField DataField="City" HeaderText="City" SortExpression="City" />
<asp:BoundField DataField="Country" HeaderText="Country" SortExpression="Country" />
<asp:BoundField DataField="Master_ID" HeaderText="Master_ID" SortExpression="Master_ID" ItemStyle-CssClass="hiddencol" HeaderStyle-CssClass="hiddencol">
<HeaderStyle CssClass="hiddencol"></HeaderStyle>
<ItemStyle CssClass="hiddencol"></ItemStyle>
</asp:BoundField>
</Columns>
<EditRowStyle BackColor="#999999" />
<FooterStyle BackColor="#5D7B9D" Font-Bold="True" ForeColor="White" />
<HeaderStyle BackColor="#5D7B9D" Font-Bold="True" ForeColor="White" />
<PagerStyle BackColor="#284775" ForeColor="White" HorizontalAlign="Center" />
<RowStyle BackColor="#F7F6F3" ForeColor="#333333" />
<SelectedRowStyle BackColor="#E2DED6" Font-Bold="True" ForeColor="#333333" />
<SortedAscendingCellStyle BackColor="#E9E7E2" />
<SortedAscendingHeaderStyle BackColor="#506C8C" />
<SortedDescendingCellStyle BackColor="#FFFDF8" />
<SortedDescendingHeaderStyle BackColor="#6F8DAE" />
</asp:GridView>
And then:
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
If Page.IsPostBack = False Then
''Set value for default SQL query
Dim query As String
query = "SELECT Sites.Master_ID AS Master_ID, Scopes.Name AS Scope, Brands.Extension AS [Brand], Sites.ID AS [Site ID], Sites.Name AS [Site Name], Sites.Address, Sites.CAP, Sites.City, Countries.Name AS Country FROM Sites INNER JOIN Scopes ON Sites.scope_ID = Scopes.ID INNER JOIN Brands ON Sites.brand_ID = Brands.ID INNER JOIN Countries ON Sites.country_ID = Countries.ID"
sid_db.SelectCommand = query
gvShow.DataSource = sid_db
gvShow.DataBind()
End If
End Sub
Protected Sub ChkSelectAll_CheckedChanged(sender As Object, e As EventArgs)
Dim a As Boolean = DirectCast(sender, CheckBox).Checked
For Each row As GridViewRow In gvShow.Rows
Dim cbx As CheckBox = row.FindControl("ChkSigleItem")
cbx.Checked = a
Next
End Sub