Filtering GridView rows not working - asp.net

Question

I've written some code in the Page_PreRender event that gets the value of a DropDownList control and then performs some conditional logic. Problem is, the logic must not be very good.
The first If.. Then.. Else.. structure is working fine, however, if the selectedItem is not "Todos" (portuguese for "all") all the rows' visibility will be set to false. The issue seems to arise when the If SelectedItem <> "Todos" Then condition is met.
So, every option in the DropDownList aside from "Todos" sets the visibility of all rows to False instead of setting the visibility of the ones that don't match the SelectedItem to False.
Protected Sub Page_PreRender(sender As Object, e As EventArgs) Handles Me.PreRender
'Getting the selected item
Dim SelectedItem As String = CType(GridView1.HeaderRow.Cells(3).FindControl("DropDownList1"), DropDownList).SelectedItem.Text
If SelectedItem <> "Todos" Then
'This is the part where the issue seems to be located.
For Each Row As GridViewRow In GridView1.Rows
'Get the Text value
Dim depar As String = Row.Cells(3).Text
'If its different from the SelectedItem then the row's visible property should be set to false, if it's a match, set it to true.
If depar <> SelectedItem Then
Row.Visible = False
ElseIf depar = SelectedItem Then
Row.Visible = True
End If
Next
'If "Todos" was selected, all rows should be visible
ElseIf SelectedItem = "Todos" Then
'Make all rows visible
For Each row As GridViewRow In GridView1.Rows
row.Visible = True
Next
End If
End Sub
Code of GridView:
<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" DataSourceID="SqlDataSource1" PageSize="20" Width="100%" >
<Columns>
<asp:TemplateField>
<ItemTemplate>
<asp:CheckBox ID="CheckBox1" runat="server" />
<asp:LinkButton ID="LinkButton1" runat="server" CommandArgument='<%#CType(Container, GridViewRow).DataItem("IdPedido") %>' OnClick="LinkButton1_Click" OnCommand="LinkButton1_Command">Ver</asp:LinkButton>
</ItemTemplate>
<HeaderStyle Width="40px" />
</asp:TemplateField>
<asp:BoundField DataField="Observacoes" HeaderText="Assunto" SortExpression="Observacoes" />
<asp:BoundField DataField="NomeHotel" HeaderText="Hotel" SortExpression="NomeHotel" />
<asp:TemplateField HeaderText="Departamento" SortExpression="NomeDepartamento">
<HeaderTemplate>
Departamento<br />
<asp:DropDownList ID="DropDownList1" runat="server" AppendDataBoundItems="True" DataSourceID="SqlDataSource1" DataTextField="NomeDepartamento" DataValueField="IdDepartamento" AutoPostBack="True" OnLoad="DropDownList1_Load" OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged">
<asp:ListItem>Todos</asp:ListItem>
</asp:DropDownList>
<asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:EnotelSuporteConnectionString1 %>" SelectCommand="SELECT [NomeDepartamento], [IdDepartamento] FROM [Departamentos]"></asp:SqlDataSource>
</HeaderTemplate>
<EditItemTemplate>
<asp:TextBox ID="TextBox1" runat="server" Text='<%# Bind("NomeDepartamento") %>'></asp:TextBox>
</EditItemTemplate>
<ItemTemplate>
<asp:Label ID="Label1" runat="server" Text='<%# Bind("NomeDepartamento") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:BoundField DataField="DataPedido" HeaderText="Data" DataFormatString = "{0:dd, MMM yyyy}" SortExpression="DataPedido" />
<asp:BoundField DataField="DataFinalizado" HeaderText="Finalizado a" DataFormatString = "{0:dd, MMM yyyy}" SortExpression="DataFinalizado" />
<asp:BoundField DataField="Nome" HeaderText="Nome" SortExpression="Nome" />
<asp:BoundField DataField="Estado" HeaderText="Estado" SortExpression="Estado" Visible="False" />
<asp:BoundField DataField="IdPedido" HeaderText="IdPedido" InsertVisible="False" ReadOnly="True" SortExpression="IdPedido" Visible="False" />
</Columns>
</asp:GridView>

Answer 1

THe problem in your Row.Cells(3).Text is that you are defining the ItemTemplate in your gridview with Label and to get the ItemTemplates value you have to first find the control and then get the value from that control.
If you want the value of the label then use the following code to get the value,
Label label = (Label)Row.Cells(3).FindControl("Label1");
if(label != null)
string depar = label.Text;
NOTE
Code is in the c# you might want to convert it to the VB.