No client side password matching on MVC view

Question

I have the following (abridged) DTO for registering a new user:

[PropertiesMustMatch("Password", "ConfirmPassword", ErrorMessage = "The password and confirmation password do not match.")]
public class RegisterModel
{
    //.....
    [DataType(DataType.Password)]
    public string Password { get; set; }
    [DataType(DataType.Password)]
    public string ConfirmPassword { get; set; }
}

This is then wrapped in a View Model as such:

public class RegisterModelViewData: BaseViewData
{
    public RegisterModel RegisterModel { get; set; }
    public int PasswordLength { get; set; }
}

And finally, on the view, I have the two fields as such:

<div class="editor-field">
    <%= Html.PasswordFor(m => m.RegisterModel.Password) %>
    <%= Html.ValidationMessageFor(m => m.RegisterModel.Password) %>
</div>
<div class="editor-field">
    <%= Html.PasswordFor(m => m.RegisterModel.ConfirmPassword) %>
    <%= Html.ValidationMessageFor(m => m.RegisterModel.ConfirmPassword) %>
</div>

Apparently, I am supposed to get a client side validation, and no post, if the passwords don't match. I get a post and then a message that "Account creation wAs unsuccessful", but nothing about mismatched passwords. I have omitted the Required and MininumLength attributes from the password proeprties here for brevity, but they seem to behave as expected and validate on the client.

Answer 1

Now available in ASP.MVC 3 in case anyone is still wondering

public string Password { get; set; }
[Compare("Password", ErrorMessage = "Passwords must match")]
public string ConfirmPassword { get; set; }