RegularExpressionValidator for textbox inside GridView not working

Question

I have GridView:

<asp:GridView ID="MyGridView" runat="server" ShowFooter="true"
                                AutoGenerateColumns="False" Visible="True">
<Columns>
<asp:BoundField DataField="id" ItemStyle-HorizontalAlign="center"/>
<asp:BoundField DataField="fullName"  />
<asp:TemplateField HeaderText="situation>">
<ItemTemplate>
  <asp:DropDownList ID="dl_situation" runat="server">
   </asp:DropDownList>
</ItemTemplate>
</asp:TemplateField>

<asp:TemplateField>
 <ItemTemplate>
         <asp:TextBox ID="tbNr" runat="server"></asp:TextBox>
</ItemTemplate>
</asp:TemplateField>  
<asp:TemplateField HeaderText="Data">
<ItemTemplate>
 <asp:TextBox ID="tbDate" runat="server"></asp:TextBox>
 </asp:RequiredFieldValidator>
 </ItemTemplate>
</asp:TemplateField>     
</Columns>
</asp:GridView>

It work fine, but when I add RegularrExpressionValidator for textbox with id="tbDate" mygrid does not work This regular expression must accept datetime in format "dd.MM.yyyy"

 <asp:GridView ID="MyGridView" runat="server" ShowFooter="true"
                                AutoGenerateColumns="False" Visible="True">
<Columns>
<asp:BoundField DataField="id" ItemStyle-HorizontalAlign="center"/>
<asp:BoundField DataField="fullName"  />
<asp:TemplateField HeaderText="situation>">
<ItemTemplate>
  <asp:DropDownList ID="dl_situation" runat="server">
   </asp:DropDownList>
</ItemTemplate>
</asp:TemplateField>

<asp:TemplateField>
 <ItemTemplate>
         <asp:TextBox ID="tbNr" runat="server"></asp:TextBox>
</ItemTemplate>
</asp:TemplateField>  
<asp:TemplateField HeaderText="Data">
<ItemTemplate>
 <asp:TextBox ID="tbDate" runat="server"></asp:TextBox>
 <asp:RegularExpressionValidator ID="RegularCert" runat="server" 
      ControlToValidate="tbDate" ErrorMessage="Incorect Data" 
 ValidationExpression=
"(0[1-9]|[12][0-9]|3[01])[-.](0[1-9]|1[012])[-.](19|20)[0-9]{2}" 
      Display="Dynamic"></asp:RegularExpressionValidator>
     <asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" 
      ErrorMessage="*" ControlToValidate="tbDate">
   </asp:RequiredFieldValidator>
 </ItemTemplate>
</asp:TemplateField>     
</Columns>
</asp:GridView>

Answer 1

I changed ClientIDMode to Predictable for TextBox, RegularExpressionValidator and RequiredFieldValidator and began to work