RegularExpressionValidator bound Textbox never valid within DetailsView

Question

Hello I have been having trouble with this for a while now. I have a bound textbox within a DetailsView that I have added a RegularExpressionValidator to. However after running the Web form I discovered that the value is never considered valid even when it should be. The field should only validate when the value is empty or exactly 3 uppercase letters. If I enter 'CBA' which should work I'm getting this expression as the errormessage: ^[A-Z]ABC$ where ABC is the value the field has from the datasource. So I guess it has something to do with the Eval() function inside the DetailsView but I fail to understand what exactly and how to avoid it.

<EditItemTemplate>
  <asp:TextBox ID="TBDepartFrom" runat="server" Text='<%# Bind("DepartFrom") %>'>
  </asp:TextBox>
  <asp:RegularExpressionValidator
       ID="RegularExpressionValidator1" ControlToValidate="TBDepartFrom" 
       runat="server"
       ErrorMessage="This code is invalid!" 
       Text='<%# Eval("DepartFrom", "^[A-Z]{3}$") %>'>
  </asp:RegularExpressionValidator>
</EditItemTemplate>

Answer 1

Your RegularExpressionValidator needs an ValidationExpression. You are putting the expression into the Text field instead.

<EditItemTemplate>
    <asp:TextBox ID="TBDepartFrom" runat="server" Text='<%# Bind("DepartFrom") %>'></asp:TextBox>
    <asp:RegularExpressionValidator
        ID="RegularExpressionValidator1" ControlToValidate="TBDepartFrom" 
        runat="server"
        ErrorMessage="This code is invalid!"
        ValidationExpression="^[A-Z]{3}$"
        Text="*"></asp:RegularExpressionValidator>
</EditItemTemplate>