.net - input name and id changes when set runat=server

Question

In my form I need to insert different inputs of type "text". The inputs must be html controls with name and id's. Because I send this form to a external url.

For the validation I do runat=server in all inputs and then I can use requiredfieldvalidator.

But the problem is when I look in the source after visiting the page the name and id's are all changed. for example

<input id="first_name" class="formright" type="text" name="first_name" runat="server" />

changes to

<input name="ctl00$cphContent$first_name" type="text" id="ctl00_cphContent_first_name" class="formright">

I have to use html controls because the external postbackurl looks at the name and id values to find the control. So I can't use asp controls. It is because of that I used html controls with runat=server

I appreciate any help

Answer 1

This is because you're using MasterPages.

Controls contained within a content page take on a dynamic ID based on the Master Page hierarchy in order to avoid duplication of IDs.

If you need to reference the control IDs and names in client-side script, you can use <%= first_name.ClientID %>.

If you're using .NET4 you can use ClientIDMode="Static" to make the generated IDs consistent, although this comes with its own ID-conflict caveats when, for example, using multiple instances of the same user control on a page. Rick Strahl outlines those here.

However, if you're using ASP.NET validators then everything should be fine. Instead of using an HTML input you should use an ASP.NET TextBox control:

<asp:TextBox id="first_name" runat="server" CssClass="formright" />