Yesterday I got the following error:
Parser Error Message: The base class includes the field ‘IFrame’, but its type (System.Web.UI.HtmlControls.HtmlIframe) is not compatible with the type of control (System.Web.UI.HtmlControls.HtmlGenericControl).
Line 14: <iframe id=”IFrame” frameborder=”0″ runat=”server” visible=”false”/>
You need to recompile the code using the .net 4.5 runtime.
And when doing this, you need to change the *.designer.cs file reference from:
protected global::System.Web.UI.HtmlControls.HtmlGenericControl IFrame;
protected global::System.Web.UI.HtmlControls.HtmlIframe IFrame;
A bug has been reported that the VS2012 does not make this change itself, but all I had to do was to rename the ID of the IFrame control, and VS figured it out for me.