iFrame parser error after upgrading to .NET 4.5

Question

We have recently upgraded all of our WebForms projects to .NET 4.5, and encountered a parser issue when loading pages with an iFrame element. We have corrected

Answer 1

Further (or in as a combination of the answers here).

I don't believe it's needed to actually change the tags from iframe to asp:HtmlIFrame if you have the reference to the updated System.Web.UI.HtmlControls.

I updated my web.config to remove specific versions of the tag prefix and replace it with:

<add tagPrefix="asp" namespace="System.Web.UI.HtmlControls" assembly="System.Web, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a"/>

Clean and rebuild the project and that regenerates all the designer tags for me with the correct HtmlIFrame output.

Answer 2

Look into designer file, and replace Htmliframe for HtmlGenericControl in the control that has problems.

Answer 3

My solution was to just rename the IFrame and rebuild and the designer file will be updated accordingly with the correct references.

Answer 4

We were able to fix the issue converting the

<iframe id="iframe" runat="server" />

to

<asp:HtmlIframe id="iframe" runat="server" />

Answer 5

Check that you have next settings in your config file. Also make sure that it's there after publishing.

<system.web>
    <httpRuntime targetFramework="4.5" />
    <compilation debug="true" targetFramework="4.5"/>
    ...
</system.web>

Hope it's should help.

Answer 6

From .NET 4.5, Microsoft decided to change the iframe from a HtmlGenericControl to its own control, a HtmlIframe. so you have to change the

System.Web.UI.HtmlControls.HtmlGenericControls to System.Web.UI.HtmlControls.HtmlIframe