Hi Björn, did you solve this?

Nope, still same problem... Cant open to choose any x-form. Still getting the same error...

Anyone got any idéa?

[NullReferenceException: Object reference not set to an instance of an object.]
   EPiServer.Util.XFormHelper.ListFormReferences(String formId) +178
   EPiServer.UI.Edit.XFormSelect.GetxFormUsedonPages(String formId) +23
   EPiServer.UI.Edit.XFormSelect.LoadForms(String folder, Boolean iListMyFormOnly, Boolean loadSelectedFormPageIndex) +665
   EPiServer.UI.Edit.XFormSelect.OnLoad(EventArgs e) +356
   System.Web.UI.Control.LoadRecursive() +50
   System.Web.UI.Control.LoadRecursive() +141
   System.Web.UI.Control.LoadRecursive() +141
   System.Web.UI.Control.LoadRecursive() +141
   System.Web.UI.Control.LoadRecursive() +141
   System.Web.UI.Control.LoadRecursive() +141
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +627

When looking at the code that throws the exception, could you please see below

Hashtable defTypeNames = new Hashtable();

          ArrayList pageDefsWithNullTypes = new ArrayList();
            foreach (PageType type in PageType.List())
                foreach (PageDefinition def in type.Definitions)
                {
                    if (def.Type == null)
                    {
                        pageDefsWithNullTypes.Add(def);
                        continue;
                    }
                    if (def.Type.Name.IndexOf("XForm") != -1 && !defTypeNames.Contains(def.Name))
                        defTypeNames.Add(def.Name, def.Name);
                }

My guess is that something is wrong in some pagetype. E.g. it could be that for some reason some property misses a Type.
My suggestion would be to try to run the following code under a debugger against your database

Hi,

I'm wonering how you solved this issue. Would be very helpful if you can help since I have the same problem after migration to CMS 6 R2.

Best regards,

Maryam

Hi,
We're also facing the same problem and therefore very interested in a solution.
Many thanks for any hints.

Best Regards
Xuan

We are also facing the same problem, Does anybody has a solution for this?

I think we had something like this and if I remember correctlu it was a broken pagetypedefinition in the databas. Strange enouggh both creating new and browsing already existing pages of the offending type worked. 

Thank you for your help. Especially Huy and Per Nergård. I didn't get your answers at the first sight. But after using reflection on the method EPiServer.Util.XFormHelper.ListFormReferences(string formId) and debugging its code I finally understood Huy's hint. 

There could be any broken Pagetype which interferes with the xform functionality. That is really a painful side effect.

So to wrap it up: Just click all the pagetype in the backend admin pagetype section to verify if they work. After identifying the culprit try to remove him carefully from the database.