Buttonfield and gridview and no reaction

Question

I have a gridview and in this gridview there is a buttonfield.

<asp:GridView ID="OrdersGridView" runat="server" AutoGenerateColumns="False" 
                    onrowdeleted="OrdersGridView_RowDeleted" 
                    onrowcommand="OrdersGridView_RowCommand">
   <Columns>
     <asp:TemplateField HeaderText="Product Name">
       <ItemTemplate>
          <asp:HiddenField runat="server" ID="HiddenField1" Value='<%#Eval("oid")%>'></asp:HiddenField>
       </ItemTemplate>
     </asp:TemplateField>
     <asp:BoundField DataField="titel" HeaderText="Name" />
     <asp:BoundField DataField="oid" HeaderText="Itemno" />
     <asp:BoundField DataField="prijs" HeaderText="Price" />
     <asp:ButtonField ImageUrl="Images/close.jpg" CausesValidation="false" HeaderText="Update" Text="Delete" commandname="Del" runat="server"  />
     <asp:BoundField DataField="prijs" HeaderText="Subtotal" />
    </Columns>
  </asp:GridView>

Im testing this buttonfield with the next code

protected void OrdersGridView_RowCommand(object sender, GridViewCommandEventArgs e)
{
    Check.Text = "test1";
    if (e.CommandName == "Del")
    {
        string sValue = ((HiddenField)OrdersGridView.SelectedRow.Cells[1].FindControl("HiddenField1")).Value;
        Check.Text += sValue;
    }
    else
    {
        Check.Text += "test2";
    }
}

But nothing happens when I click on the buttonlink. the label Check stays empty. What am I doing wrong?