I get the same thing as well for all properties that are not mandatory in Umbraco. Say for instance i got a DateTime field on my type, but i don't have to fill it out in Umbraco i get a conversion-error when trying to use Linq2Umbraco. If i change the type to DateTime? (nullable) i get another conversion error as well.

There seems to be missing some kind of value-checking when populating data. Like if the field in Umbraco is empty and the field is not mandatory, well, just ignore it then... it shouldn't throw an error. The same case if the field wasn't found at all, which is the case when adding new properties after nodes are created....

Posting error messages makes it easier to try and solve the problem

Stack Trace of error displaying if I don't save and publish every page with the changed Document type:


[NullReferenceException: Object reference not set to an instance of an object.]
   umbraco.Linq.Core.Node.NodeDataProvider.LoadFromXml(XElement xml, T node) +2905
   umbraco.Linq.Core.Node.d__6.MoveNext() +767
   System.Linq.WhereSelectEnumerableIterator`2.MoveNext() +147
   System.Collections.Generic.List`1..ctor(IEnumerable`1 collection) +471
   System.Linq.Enumerable.ToList(IEnumerable`1 source) +79
   Foo.Web.UserControls.MainNavigation.OnLoad(EventArgs e) in C:\projects\foo\Foo.Web\Usercontrols\MainNavigation.ascx.cs:33
   System.Web.UI.Control.LoadRecursive() +70
   System.Web.UI.Control.LoadRecursive() +189
   System.Web.UI.Control.LoadRecursive() +189
   System.Web.UI.Control.LoadRecursive() +189
   System.Web.UI.Control.LoadRecursive() +189
   System.Web.UI.Control.LoadRecursive() +189
   System.Web.UI.Control.LoadRecursive() +189
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +3047

Posting answer or comment makes it easier to try and solve the problem

Pauli, the comment posted by Daniel Eriksson is the same stack trace I got when I added a new property.

I also get an error, but mine is different. I'm using Linq to Umbraco with my own NodeDataProvider which i pass a custom path to the XML file in. It works when there are no properties added to a doc type, but as soon as there are properties i get this exception

[NullReferenceException: Object reference not set to an instance of an object.]
   umbraco.BusinessLogic.User.setupUser(Int32 ID) +201
   umbraco.BusinessLogic.User..ctor(Int32 ID) +238
   umbraco.UmbracoSettings.ensureSettingsDocument() +773
   umbraco.UmbracoSettings.GetKey(String Key) +61
   umbraco.UmbracoSettings.get_ForceSafeAliases() +69
   umbraco.cms.helpers.Casing.SafeAliasWithForcingCheck(String alias) +49
   umbraco.Linq.Core.Node.NodeDataProvider.LoadFromXml(XElement xml, T node) +2836
   umbraco.Linq.Core.Node.NodeTree`1.GetEnumerator() +1057
   ASP.views_site_latestmediaentries_ascx.__Render__control1(HtmlTextWriter __w, Control parameterContainer) in d:\~FARMPROJECTS\WMA0007 - Linkin Park\branches\v1.0-MAINLINE\LinkinPark.v2\LinkinPark.Web\Views\Site\LatestMediaEntries.ascx:6
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +130
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +245
   System.Web.Mvc.ViewPage.Render(HtmlTextWriter writer) +84
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +5273

Are you overriding NodeDataProvider or UmbracoDataProvider?

If you're using your own custom XML document then you should override UmbracoDataProvider

I've added a change so that if the node hasn't been republished you wont have an exception thrown on new properties, they'll just be set to null, this matches what NodeFactory.Node works.

Great!

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