.NET user control not loading under https

keywords: .net user control, activex, ocx, IE7, IE, https, http, secure

Justin and I just had a heck of a week fighting ActiveX controls developed using C# in .NET 2.0, so we will be blogging about some of the issues that we found and their solutions (so we can remember later), the first one is about ActiveX controls running under https.

We developed our control, everything was fine, one of our clients wanted to try that over a secure site, so we said no problem... until we tried, and tried, and tried, and nothing worked, the control would just not load.

the solution ended up being really stupid (as is usually the case); when you include your control, you usually do something like this:

<object id="someId" classid="SomeDll#Namespace.ClassName"></object>

that's the way you'll find it in all the examples around the web, and that will work just fine (once you get past all the other stuff that is required to make it work) under http, but when you move that to https, it will simply not work.

the solution?

when you create your control, you assign a guid to it

[Guid("CAE67AEA-F489-4e52-956B-CCC774F40A3A")]
[ClassInterface(ClassInterfaceType.None), ComSourceInterfaces(typeof(IControlEvents))] // --Expose events
[ComVisible(true)]
public partial class MyControl : UserControl...

something like that...
well, to make it work on https, you simply have to use that GUID, not the class name, so you would just write this on your html code

<object id="someId" classid="clsid:CAE67AEA-F489-4e52-956B-CCC774F40A3A"></object>

done, hope we saved you hours of headache